Application letter project development intern-kenya

ACF - INTERNATIONAL NET WORK

The subsistence fishfarming
in Africa: Technical Manual

Yves FERMON

In collaboration with:

Aımara

Cover photos:
Ö Top right: Tilapia zillii - © Anton Lamboj
Ö Top left: Pond built by ACF in DRC, 2008 - © François Charrier
Ö Bottom: Beneficiaries in front of the pond they have done, Liberia, ASUR, 2006 - © Yves Fermon

ii Subsistence fishfarming in Africa

OBJECTIVES OF THE MANUAL
Ö The objective of the handbook is to bring to the essential elements for the installa-
tion of production of animal proteins “fish” to lower costs in relation to the existing
natural resources and with a minimum of external contributions. This in a context of
subsistence.

Ö In this case, it is a question above all of proposing an information system strategic
plan of a system making it possible to produce consumable fish in the shortest pos-
sible time, and with lower costs to mitigate the lack of animal proteins. This does not
prevent the installation of structures having a certain durability. The unit must be
adapted to the environmental context.
In this work, it is a question of providing a guide:
¾ To program managers and their technical teams,
¾ To managers at headquarters to monitor the success of programs.

This manual covers:
Ö The various stages of setting up a «fishfarming» program,
As of the arrival on the ground, it is a question of evaluating the renewable resources present, the
needs for the populations and the already existing supply in fish. Then, a whole process is connected
involving the technical sides of the installation of fish ponds, follow-ups of the biological aspects
of the ponds. Finally, it is a question of managing and of carrying out a follow-up of the ponds and
production of fish.
Ö The constraints that must be taken into account by the field actors.
Various constraints will influence the choice for the development of fish production or not and
what kind of techniques for a good fit with human needs and the environment. They are environmen-
tal, in conjunction with the available resources, geomorphology, climate and hydrology of the area of
intervention. But they are also a social and cultural development, with the beliefs and taboos, land
issues and laws. The fact that, according the region of intervention, the ethnic and social groups and
countries, modes of intervention will be different.

WHY ANOTHER HANDBOOK?
Several organizations have published manuals for the establishment of fish farms in Africa.
The first books calling systems in place at the time of the colonial system, but as a fish produc-
tion for food self-sufficiency. However, after many trials, the majority of them has proved unsustai-
nable in the longer term, for various reasons.
The studies undertaken by different agencies of national or international research as the World-
Fish Center (formerly ICLARM), CIRAD, IRD (ex ORSTOM), Universities of Louvain and Liège ... have
provided evidence concerning the failures and have provided solutions and contributions to knowle-
dge in both technical, social or biological species used.
However, looking at all the works, one can put forward four points:
9 Most handbooks are intended for production systems of fish for sale, involving:
¾ A temporal investment which can become important and which leads to a professio-
nalisation. This requires a technology with the appropriate training of technicians on aspects of
reproduction, nutrition or health of fish, either for the establishment of systems to produce food
to feed all the fish... Application requires external inputs whose supply may become a barrier for
small producers.
¾ Financial investment for, sometimes, land, establishment of ponds, the use of workers,
qualified technicians…

Subsistence fishfarming in Africa III

9 The handbooks do not take account of the local biodiversity. Indeed, many introductions and
movements of species were made with the intention to set up farms and caused significant disrup-
tion to the balance of ecological systems.
9 Whereas these documents present solutions which appear universal, the great variation of
the geomorphology, hydrology and the climate in Africa will make that there exist conditions very
different according to the zones from interventions.
9 Few works also reflect the socio-ethnological aspects. Educational levels, beliefs and
cultures of different peoples and the appropriation of this type of project by the people is often put
forward, despite real progress in recent years.
9 Most of these books are made for aspects related to development and therefore with a po-
tentiality of longer temporal installation.

LIMITS OF THIS HANDBOOK
This handbook is primarily a guide to give to the actors the stages and procedures to be
followed. However, it will be necessary to adapt these stages and procedures according to the
context in which the actions will be undertaken:
9 From a social, cultural and political point of view
¾ Culture and belief
Food taboos exist, to varying degrees in all cultures. It is obvious that food, the basic element
for the subsistence of man, is a field where the distinction between allowed and forbidden, the pure
and impure, is fundamental for health reasons, moral or symbolic systems.
¾ Local law
Each country is governed by laws concerning wildlife protection and movement of species from
one region to another. These laws can be enacted at the regional level and at all administrative levels,
to the village itself. They may be linked to land issues.
9 From an environmental point of view:
¾ Biodiversity and available resources
The fauna of African fish includes over 3200 described species belonging to 94 families, but all
are not exploitable. The distribution is not uniform across the continent and some species are known
only of well delimited zones. For example, the African Great Lakes have a fauna whose majority of
the species are endemic there. This means to act with a good knowledge of the fauna compared to
the potentially exploitable species and the ecological risks of damages that could be related to the
establishment of a fishfarming.
¾ Geomorphology, climate and hydrology
If wildlife is so diverse across the continent, it is the result of historical and geological events
that led Africa over millions of years. This has caused major hydrological changes. On a smaller time
scale, climate variations are crucial for the viability of a fish. The availability of water, with its different
uses (drinking, domestic, agriculture ...) is a limiting factor and a source of conflict. The type of terrain
and the nature of the soils of the region will lead to technical problems for the achievement of the
pond it will be solved.

THE STEPS
The first handbook is intended for internal use to Action Against Hunger network, therefore,
with restricted diffusion. If possible and requests, a handbook with corrections and revisions will be
proposed later. Then, an external diffusion to ACF could be considered.

iv Subsistence fishfarming in Africa

ACRONYMS

ACF/AAH: Action Contre la Faim / Action Against Hunger

AIMARA: Association de spécialistes oeuvrant pour le développement et
l’application des connaissances sur les poissons et les rela-
tions Homme-Nature

APDRA-F: Association Pisciculture et Développement Rural

ASUR: Association d’Agronomie et Sciences Utiles à la Réhabilitation
des populations vulnérables

CIRAD: Centre de coopération Internationale en recherche Agrono-
mique pour le Développement

CNRS: Centre national de la recherche scientifique

FAO: Food and Agriculture Organization of the United Nations

IRD: Institut de Recherche pour le Développement

MNHN: Muséum national d’Histoire naturelle

UNO: United Nation Organisation

NGO: Non Governemental Organisation

GIS: Geographic Informatic System

BDC: Biological Diversity Convention

IBI: Integrity Biological Indice

DRC: Democratic Republic of Congo (ex-Zaïre)

Subsistence fishfarming in Africa V

Aımara
Association of specialists working for the development and the
application of knowledge on fish and Man-Nature relationships

The aquatic environments and the management of water represent one of the major stakes for the
decades to come.
The fish are a source of proteins of good quality for the human consumption, but also a source of
income considerable for the developing as developed countries.
However, demography, the urban development, the installation of the rivers, industrialization, the
climate changes, deforestation… have irreversible consequences on the water courses and the biodi-
versity and thus on the men who live of these resources.

Ö Goals
Research
9 To acquire new ichthyologic knowledge - systematic, biology, ecology, ethology… - on
the fresh water, brackish and marine species;
9 To highlight knowledge and practices relating to fishing and management of the biodi-
versity and their modes of transmission.
Diffusion of knowledge
9 To disseminate the results to the local populations, the general public and the scientific
community by publications, exhibitions, contacts with the media and Internet.
Sustainable management of environment and resources
9 To sensitive by using the social, cultural, food, economic and patrimonial values of the
species with the aim of the conservation, of the management and of the preservationof the
biodiversity;
9 To collaborate with the local actors in the durable management of the aquatic resources.

Ö Scope of activities
• Studies of the characteristics of environments and impacts;
• Studies of the biology, biogeography, ecology and behavior of species;
• Anthropological and socio-economic relations man - Nature studies;
• Ecosystem modeling, statistical analysis:
• Development of databases;
• Expertise and faunistic inventories. Association AÏMARA
50 avenue de La Dhuys
93170 Bagnolet - FRANCE
association.aimara@gmail.com

vi Subsistence fishfarming in Africa

ACKNOWLEDGEMENTS

Ö ACF
Devrig VELLY - Senior Food Security advisor, AAH

Cédric BERNARD - Food Security advisor in DRC, AAH

François CHARRIER - Food Security advisor in DRC, AAH, Rereader
Ö Aimara
François MEUNIER - Emeritas Professor at MNHN, President of AIMA-
RA, Rereader

Patrice PRUVOST - Secretary of AIMARA

Hélène PAGÉZY - Researcher, CNRS
Ö Other collaborators
Roland BILLARD - Emeritas Professor at MNHN, Rereader

Didier PAUGY - Research Director at IRD

Thierry OBERDORFF - Research Director at IRD

Jérome LAZARD - Research Director at IRD

Alain BARBET - Agronomist

Anton LAMBOJ - Researcher, University of Vienna, Austria.

Mickael NEGRINI - Fishfarming technician

Kirk WINNEMILLER - Researcher, University of Texas, USA

Étienne BEZAULT - Researcher, EAWAG, Switzerland

Fabien NANEIX - Teacher

Subsistence fishfarming in Africa VII

CONTENTS

Part I - INTRODUCTION AND THEORICAL ASPECTS 1
Chapter 01 - FISHFARMING: AIM AND ISSUES 3
I. WHY? 3
II. PRESSURE ON THE RESOURCES 6
II.1. Modifications of the habitat 6
II.2. Water pollution 8
II.3. Fisheries impact 9
II.4. Introductions 9
III. INTERNATIONAL ASPECTS 12
IV. OBJECTIVE OF FISHFARMING 13

Chapter 02 - TYPE OF FISHFARMING 15
I. VARIOUS TYPES OF FISHFARMING 15
II. SOME HISTORY… 17
III. A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE 17
IV. POLYCULTURE VS MONOCULTURE 18

Chapter 03 - BIOGEOGRAPHY AND FISH SPECIES 21
I. GEOGRAPHY 21
II. THE SPECIES 21
II.1. The Cichlidae 22
II.2. The Siluriformes or catfishes 23
II.3. The Cyprinidae 23
II.4. Other families and species 24

SUMMARY - PART 01 25

Part II - PRACTICAL ASPECTS 27
Chapter 04 - THE INITIAL PRE-PROJECT ASSESSMENT 33
I. THE ECOSYSTEM 33
II. THE ASSESSMENT 36
III. PRINCIPLE 37
IV. BIOLOGICAL AND ECOLOGICAL ASSESSMENT 38
V. SOCIO-ETHNOLOGY 40
V.1. Socio-economic and cultural characteristics 40

viii Subsistence fishfarming in Africa

V.2. The relations man-resources 40
V.3. The relations man-man 41

Chapter 05 - VILLAGES AND SITES SELECTIONS 43
I. THE VILLAGES SELECTION 43
II. THE SITES SELECTION 45
II.1. The water 45
II.2. The soil 50
II.3. The topography 53
II.4. The other parameters 56
Chapter 06 - CHARACTERISTICS OF THE PONDS 59
I. DESCRIPTION 59
II. TYPES OF PONDS 59
II.1. Barrage ponds 62
II.2. Diversion ponds 62
II.3. Comparison 62
III. CHARACTERISTICS 63
III.1. General criteria 63
III.2. Pond shape 66
III.3. According the slope 67
III.4. Layout of ponds 67
III.5. Size and depth of the ponds 68
III.6. Differences in levels 69
IV. SUMMARY 71
Chapter 07 - THE CONSTRUCTION OF POND 73
I. THE DESIGN PLAN 73
II. THE CLEANING OF THE SITE 75
III. WATER SUPPLY: WATER INTAKE AND CHANNEL 77
IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE 81
V. THE PICKETING OF THE POND 82
VI. THE CONSTRUCTION OF THE DIKES 83
VII. THE DEVELOPMENT OF THE PLATE (BOTTOM) 89
VIII. THE CONSTRUCTION OF THE POND INLET AND OUTLET 90
VIII.1. Pond inlet structures 90
VIII.2. Pond outlet structures 94
VIII.3. Sedimentation tank 105
Ix. ADDITIONAL INSTALLATIONS 106
Ix.1. The anti-erosive protection 106
Ix.2. The anti-erosive fight 107
Ix.3. Biological plastic 108

Subsistence fishfarming in Africa Ix

Ix.4. The fence 108
Ix.5. The filling of the pond and tests 109
x. NECESSARY RESOURCES 109
x.1. Materials 109
x.2. Human Resources and necessary time 110
xI. SUMMARY 112

Chapter 08 - BIOLOGICAL APPROACH 113
I. THE LIFE IN A POND 113
I.1. Primary producers 115
I.2. The invertebrates 116
I.3. The vertebrates 118
II. THE FERTILIZATION 118
II.1. The fertilizers or manure 118
II.2. The compost 121
III. SUMMARY 126

Chapter 09 - THE HANDLING OF THE FISH 127
I. CATCH METHODS 127
I.1. Seine nets 129
I.2. Gill nets 132
I.3. Cast nets 133
I.4. Dip or hand nets 134
I.5. Traps 135
I.6. Handline and hooks 136
II. THE TRANSPORT OF LIVE FISH 136
III. THE PRODUCTION OF FINGERLINGS OF TILAPIA 139
III.1. The recognition of the sex 139
III.2. The nursery ponds 139
III.3. Hapas and cages 142
III.4. The other structures 145
IV. THE STOCKING OF THE PONDS 146
V. THE FOLLOW-UP OF FISH 149
VI. DRAINING AND HARVEST 150
VI.1.Intermediate fishings 150
VI.2. Complete draining 151
VII. SUMMARY 152

Chapter 10 - MAINTENANCE AND MANAGEMENT OF THE PONDS 153
I. THE MAINTENANCE OF THE PONDS 153
I.1. The diseases of fish 153
I.2. The feeding of the fish 158
I.3. Daily activities of follow-up 162
I.4. Maintenance work after draining 163

x Subsistence fishfarming in Africa

I.5. Fight against predators 164
I.6. Summary 164
II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION 165
III. THE MANAGEMENT OF PONDS 167
III.1. Fish Stocks and useful indices for monitoring 167
III.2. The expected yields 168
III.3. The management of harvests 168
III.4. Several kinds of production costs 170
III.5. Record keeping and accounting 170
III.6. The formation 171
IV. PONDS AND HEALTH 171
GENERAL SUMMARY 173
REFERENCES 177
GLOSSARY 179
APPENDIx 187
Appendix 01 - ExAMPLES OF FILES 189
I. FILES FOR MONITORING THE PONDS 189
II. FILES FOR THE FOLLOW-UP OF THE FISH 191

Appendix 02 - TABLE OF DATA 193
Appendix 03 - SOME ELEMENTS OF THE BIOLOGY OF THE SPECIES 207
I. THE MORPHOLOGY AND THE SYSTEMATIC 207
II. THE BIOLOGY OF CICHLIDAE 216
II.1. The taxonomy 216
II.2. The feeding habits 217
II.3. The reproduction and parental care 218
III. THE BIOLOGY OF SILURIFORMES OR CATFISH 226
III.1. The Clariidae 226
III.2. The Claroteidae and Auchenoglanididae 231
III.3. The Schilbeidae 233
III.4. The Mochokidae 233
IV. THE OTHER FAMILIES 234
IV.1. The Cyprinidae 234
IV.2. The Citharinidae 234
IV.3. The Distichodontidae 236
IV.4. The Channidae 236
IV.5. The Latidae 237
IV.6. The Arapaimidae 237
Appendix 04 - BIOGEOGRAPHIC DATA 239
Appendix 05 - FILE OF SPECIES 255

Subsistence fishfarming in Africa xI

LIST OF FIGURES
Figure 1. World capture and aquaculture production (FAO, 2007). 3
Figure 2. Inland capture fisheries by continent in 2004 (FAO, 2007). 5
Figure 3. Aquaculture production by regional grouping in 2004 (FAO, 2007). 5
Figure 4. Relative contribution of aquaculture and capture fisheries to food fish consumption (FAO, 2007). 6
Figure 5. GIS assessment of potential areas for production fish farms in Africa. 14
Figure 6. Continuum Aquaculture - Fishery en relation with the investment intensification. 19
Figure 7. The ichthyoregions and the countries. 22

Figure 8. General implementation plan. 32
Figure 9. Setting of fish ponds: 1. Assessment. 34
Figure 10. Water cycle. 35
Figure 11. Contextual components of the assessment. 36
Figure 12. Setting of fish pond: 2. Selections. 44
Figure 13. Volume of a pond. 46
Figure 14. Water loss through evaporation by weather. 46
Figure 15. Water loss by ground. 46
Figure 16. Flow measurement for small rivers. 47
Figure 17. Measurement of section of the river. 47
Figure 18. Measurement of speed V of the river. 47
Figure 19. Examples of factors that may affect water quality. 48
Figure 20. Secchi disk. 49
Figure 21. Impermeability of clay and sandy soils. 50
Figure 22. Test of the ball (1). 51
Figure 23. Test of the ball (2). 51
Figure 24. Test of soil permeability. 52
Figure 25. Identification of potential water supplies, drainage options, individual valleys, comparison of the
various good sites for the installation of ponds, vision of the bottoms (CIRAD). 53
Figure 26. Water supply by gravity. 54
Figure 27. Type of slopes and constraints. 55
Figure 28. Hill slope. 55
Figure 29. Measurement of a slope: Device. 57
Figure 30. Measurement of a slope: Calculation. 57
Figure 31. Example of location of a pond in relation of the house. 58
Figure 32. Setting of fish pond: 3. Ponds. 60
Figure 33. Main components of a pond. 61
Figure 34. Cross section of a ponds. 61
Figure 35. Examples of barrage ponds. 64
Figure 36. Examples of diversion ponds. 65
Figure 37. Disposition of ponds in relation to the topography (CIRAD). 66
Figure 38. Optimization of the surface / work (CIRAD). 66
Figure 39. Example of pond whose shape is adapted to the topography. 67
Figure 40. Disposition and shape of ponds according the slope. 67
Figure 41. Layout of ponds. In series; In parallel. 67
Figure 42. Maximal and minimal depth of a pond. 69
Figure 43. The different points for the management of water by gravity. 70
Figure 44. Level differences. 70
Figure 45. Classical plan a diversion ponds. 71
Figure 46. Examples of diversion fishfarm. 72

xii Subsistence fishfarming in Africa

Figure 47. Setting of fish pond: 3. Ponds. 74
Figure 48. Visualization by picketing of the first plan of possible water supply, possible drainage, of diffe-
rents valley (CIRAD). 75
Figure 49. Preparation of the site of the pond. 76
Figure 50. Cleaning of the site. 76
Figure 51. Water levels differences. 78
Figure 52. Setting of the water supply channel. 79
Figure 53. Transverse profile of the channel. Measure and slope of sides. 79
Figure 54. Channel digging. 80
Figure 55. Setting of draining channel. 81
Figure 56. Level of draining channel. 81
Figure 57. Picketing of the pond and the dikes. 82
Figure 58. Cleaning of the zones where the dikes will be build. 83
Figure 59. Definition of the different types of dikes. 83
Figure 60. Description and proportion of a dike (of 1 m high). 83
Figure 61. Pressure difference on a dike. 84
Figure 62. Dikes. Good high; Dikes too small. 84
Figure 63. Digging of the cut-off trench for clay core. 85
Figure 64. Clay core and saturation of the dikes. 85
Figure 65. High of a dike. Depth; Freeboard; Settlement. 85
Figure 66. High of the structure. 85
Figure 67. Dimension of a dike. 86
Figure 68. Calculation of the slope of the dikes. 87
Figure 69. Construction of the dikes (I). Traditionnal - By blocks. 88
Figure 70. Construction the dikes (II). 88
Figure 71. Preparation of the bottom. 88
Figure 72. The bottom or plate. Direction of the slope and drain setting: In ray; As «fish bones». 89
Figure 73. Bottom drain. 90
Figure 74. Cross cut of a pond at the bottom drain. 90
Figure 75. Cross cut of the inlet of a pond. 91
Figure 76. Pipe inlet. 91
Figure 77. End of bamboo pipe. 91
Figure 78. Gutter inlet. 92
Figure 79. Different types of gutter. 92
Figure 80. Canal inlet. 92
Figure 81. Diagram of an example of sand filter. 93
Figure 82. Turn-down pipe inside pond outlet. 95
Figure 83. Composition of a monk. 96
Figure 84. Position of the monk in the pond. 97
Figure 85. Position of the monk according the downstream dike. 97
Figure 86. Wooden monk. Small and medium size. 98
Figure 87. Wooden pipe. 99
Figure 88. Mould of a monk. Front view; Upper view. 100
Figure 89. Monk. Upper view and example of size. 101
Figure 90. Functioning of a monk. 102
Figure 91. Concrete pipe. Croos cut; Mould; Final pipe. 103
Figure 92. Setting of a pipe overflow. 104
Figure 93. Type of setting basin. Natural; In concrete. 105
Figure 94. Setting basin. Normal; Improved. 106
Figure 95. Setting of a vegetable cover on the dikes. 106
Figure 96. Dikes with plants. Vegetable garden; Small animals; Trees. 107
Figure 97. Type of erosion and soil conservation. Streaming; Infiltration; Protection channel. 107
Figure 98. Fences. In scrubs; In wood or bamboo. 108
Figure 99. Schematic life cycle of a pond. 113

Subsistence fishfarming in Africa xIII

Figure 100. Setting of fish pond: 4. Fishfarming. 114
Figure 101. Trophic pyramids. 115
Figure 102. Differents algae. 115
Figure 103. Aquatic plants. 116
Figure 104. Rotifers. 116
Figure 105. Crustaceans. 116
Figure 106. Insects. 117
Figure 107. Molluscs. 117
Figure 108. Vertebrates other than fish. 118
Figure 109. Beneficial effects of organic fertilizers. 119
Figure 110. Preparation of dry compost. 123
Figure 111. Applying animal manures to a drained pond bottom. 125
Figure 112. Applying animal manures to water-filled ponds that have been stocked (I). 125
Figure 113. Applying animal manures to water-filled ponds that have been stocked (II). 125
Figure 114. Preparation of an anaerobic compost. 125
Figure 115. Compost heap in crib in a pond. 126
Figure 116. Setting of fish pond: 4. Fishfarming and 5. End of cycle. 128
Figure 117. Diagram of a seine. 129
Figure 118. The differents steps to construct a simple seine. 130
Figure 119. Setting of the pole to hold the seine. 130
Figure 120. Construction of a central-bag seine. 131
Figure 121. Manipulation of a seine. 131
Figure 122. Gill nets. 133
Figure 123. Use of a cast net. 134
Figure 124. Different types of dip nets. 135
Figure 125. Differents types of local traps. 135
Figure 126. Fish packing in plastic bags. 138
Figure 127. Sexual differentiation of differents species. 140
Figure 128. Fingerlings produced per fish density in Oreochromis niloticus. 141
Figure 129. Fingerlings produced per females body weight in Oreochromis niloticus. 141
Figure 130. Hapas and cages. 142
Figure 131. Differents systems of reproduction of tilapia in hapas and cages. 143
Figure 132. Live fish storage in hapas or nets. 144
Figure 133. Diagram on the relationships between the stocking density, the instant growth rate (G) and the
instant yield per surface unit (Y) with and without complementary feeding. 146
Figure 134. Yield and average weight of Oreochromis niloticus at the harvest in function of initial density. 147
Figure 135. Impact of the presence of a predator (here, Hemichromis fasciatus) in fishponds. 148
Figure 136. Measurement gears. 149
Figure 137. Length - Weight relationships. 150
Figure 138. Harvest of the fish. 151
Figure 139. Examples of way to collect the fish outside of the pond. 152
Figure 140. Setting of fish pond: 5. End of cycle and start again… 154
Figure 141. Fish piping on surface; Dead fish floating on surface. 156
Figure 142. Diseases of fish. Bacterial diseases; External parasites. 156
Figure 143. Example of life cycles of fish disease factors. 157
Figure 144. Structures to facilitate the feeding. 161
Figure 145. Some predators of fish. 164
Figure 146. Differents methods of natural drying of fish. 166
Figure 147. Example of smoking method of fish. 166
Figure 148. Example of salting system. 166
Figure 149. Mosquito and snail. 172
Figure 150. Several human behavior to avoid nearby the ponds. 172
Figure 151. Cleaning of the dikes. 172

xiv Subsistence fishfarming in Africa

APPENDIx 187
Figure 152. Principal terms pertinent to the external morphology of a fish. 207
Figure 153. Different body shapes. 207
Figure 154. Cross-section of body. 208
Figure 155. Jaws. 208
Figure 156. Tooth shapes. 209
Figure 157. Fontanellae. 209
Figure 158. Barbels. 210
Figure 159. Gill slits without opercule; gill arch formed by ceratobranchial, gill rakers, hypobranchial and
epibranchial, gill filaments; external gill. 210
Figure 160. Accessory aerial breathing organs. 211
Figure 161. Pair fins. 211
Figure 162. Dorsal fin. 212
Figure 163. Caudal fin. 212
Figure 164. Different types of scales. 213
Figure 165. Lateral line. 213
Figure 166. Location of electric organs. 213
Figure 167. Principal measurements that may be taken on a fish. 215
Figure 168. External features of the Cichlidae. 216
Figure 169. Courtship and spawning in a substrate spawner Cichlidae, Tilapia zillii. 218
Figure 170. Nest of Oreochromis niloticus; Oreochromis macrochir. 219
Figure 171. Courtship and spawning in a mouthbrooder Cichlidae, Haplochromis burtoni from Lake Tanga-
nyika. 220
Figure 172. Mouthbrooding. 220
Figure 173. Example of the life cycle of a maternal mouthbrooding tilapia. 221
Figure 174. Different stages in mouthbrooders. 222
Figure 175. Comparison between fry of substrate spawners and mouthbrooders. 222
Figure 176. Relationship the weight of fish of 20 cm and the size of maturation for Oreochromis niloticus for
several geographic location. 224
Figure 177. Size class of Oreochromis niloticus according several geographic location. 224
Figure 178. Comparison of growth rate for different species in natural field by locality. 225
Figure 179. Comparison of growth rate for different species in natural field by species. 225
Figure 180. Relative Fecundity (% of total weight), % of hatching (% total eggs) of Clarias gariepinus,
monthly average rainfall and average temperature. Brazzaville. 227
Figure 181. Courtship in Clarias gariepinus. 228
Figure 182. First stages of development for Clarias gariepinus. 229
Figure 183. Several stages of larval development until 17 days. Clarias gariepinus; Heterobranchus longifi-
lis. 229
Figure 184. Compared growth of several African fish species. 230
Figure 185. Growth of Heterotis niloticus and of Lates niloticus. 238
Figure 186. The ichthyoregions and the countries. 245

Subsistence fishfarming in Africa xV

LIST OF TABLES
Table I. World fisheries and aquaculture production and utilization, excluding China (FAO, 2007). 4
Table II. Origin and number of fish species introductions in Africa. 10
Table III. Introduced species with a negative ecological effect recorded. 11
Table IV. Different levels of intensification of fishfarming systems 16
Table V. Characteristics of the two main models of farming towards the various factors of production. 17

Table VI. Color of the soil and drainage conditions of the soil. 50
Table VII. Topographical features for ponds. 54
Table VIII. Advantages and disadvantages of the barrage and diversion ponds. 63
Table IX. Differents shape of a pond of 100 m2. 66
Table X. Size of fattening ponds. 68
Table XI. Resource availability and pond size. 68
Table XII. Characteristics of shallow and deep ponds. 69
Table XIII. Diversion structures to control stream water levels. 78
Table XIV. Channel dimensions. 80
Table XV. Examples fo dimension of dikes. 86
Table XVI. Expression of values of slope according the chosen unit. 87
Table XVII. Informations on the dimensions of the monk according the size of the pond. 100
Table XVIII. Estimation of the discharge and draining duration of the pond according the diameter of the
outlet. 101
Table XIX. Inside dimensions of the monk according the diameter of the pipe. 101
Table XX. Examples of necessary time for building of ponds (man/day). 110
Table XXI. Approximate output on the works of excavation made by hand. 110
Table XXII. Example of calendar of works to do for the construction of a pond (workers of 400 men per
day). 111
Table XXIII. Example of calendar according the seasons (15 ponds) in Cameroon. 111
Table XXIV. Maximum amount of fresh solid manure per day in 100 m2 pond. 120
Table XXV. Quantity to spread per type of manure. 120
Table XXVI. Organic fertilizers commonly used in small-scale fish farming. 121
Table XXVII. Particular characteristics of composting methods. 122
Table XXVIII. Production of Oreochromis niloticus in function of the number of breeders in a pond of 4 ares
– 122 farming days. 141
Table XXIX. Levels of various nutrients in different species of fish. 158
Table XXX. Relative value of major feedstuffs as supplementary feed for fish. 159
Table XXXI. Example of formula for tilapia and catfish farming. 160
Table XXXII. Example of quantity of food to give according time per m2 of pond. 160
Table XXXIII. Feeding rate for tilapia in pond related to the size (table of Marek). 160
Table XXXIV. Examples of stop feeding per species in function of the temperature 161
Table XXXV. Monitoring. x: following; xx: fuller check or major repair; V: In drained pond only. 162
Table XXXVI. Examples of management for 4 ponds. Harvest after 3 months; After 4 months. 169
Table XXXVII. Useful life of fish farm structures and equipment (in years, assuming correct utilization) 170

xvi Subsistence fishfarming in Africa

APPENDIx 187
Table XXXVIII. The tonnage of halieutic products in 2005 per African countries (FAO, 2006). 194
Table XXXIX. The checklist of freshwater species which have been the subject of an introduction in Africa
(FAO, 2006; Fishbase, 2006). 195
Table XL. List of species introduced by African countries. 197
Table XLI. List of freshwater fish used in aquaculture by country (FAO, 2006; Fishbase, 2008). 203
Table XLII. Diet of several species of tilapia in natural waters. 217
Table XLIII. Size at sexual maturation, maximale size and longevity of different species of tilapia. 223
Table XLIV. Some characteristics of African countries. 240
Table XLV. Characteristics of ichthyoregions and lakes in Africa. 244
Table XLVI. The ichthyoregions and their repartition by country in Africa. 246
Table XLVII. The genera and species of tilapias recorded by countries. 248

LIST OF SPECIES FILE
File I. Cichlidae. - Oreochromis andersoni 256
File II. Cichlidae. - Oreochromis aureus 257
File III. Cichlidae. - Oreochromis esculentus 258
File IV. Cichlidae. - Oreochromis macrochir 259
File V. Cichlidae. - Oreochromis mossambicus 260
File VI. Cichlidae. - Oreochromis niloticus 261
File VII. Cichlidae. - Oreochromis shiranus 262
File VIII. Cichlidae. - Sarotherodon galileus 263
File IX. Cichlidae. - Sarotherodon melanotheron 264
File X. Cichlidae. - Tilapia guineensis 265
File XI. Cichlidae. - Tilapia mariae 266
File XII. Cichlidae. - Tilapia rendalli 267
File XIII. Cichlidae. - Tilapia zillii 268
File XIV. Cichlidae. - Hemichromis elongatus and Hemichromis fasciatus 269
File XV. Cichlidae. - Serranochromis angusticeps 270
File XVI. Cichlidae. - Serranochromis robustus 271
File XVII. Clariidae. - Clarias gariepinus 272
File XVIII. Clariidae. - Heterobranchus longifilis 273
File XIX. Arapaimidae. - Heterotis niloticus 274

Subsistence fishfarming in Africa xVII

LIST OF PHOTOS

Photo A. Measurement of a slope (DRC) [© Y. Fermon]. 56
Photo B. Example of rectangular ponds in construction laying in parallel (Liberia) [© Y. Fermon]. 68
Photo C. Cleaning of the site. Tree remaining nearby a pond {To avoid}(DRC); Sites before cleaning (Liberia)
[© Y. Fermon]. 77
Photo D. Channel during the digging (Liberia) [© Y. Fermon]. 80
Photo E. Stakes during the building of the dikes (Liberia) [© Y. Fermon]. 82
Photo F. Dikes. Slope badly made, destroed by erosion (DRC)[© Y. Fermon]; Construction (Ivory Coast)
[© APDRA-F](CIRAD). 89
Photo G. Example of non efficient screen at the inlet of a pond (Liberia) [© Y. Fermon]. 93
Photo H. Example of filters set at the inlet of a pond in Liberia [© Y. Fermon]. 93
Photo I. Mould and monks (Guinea). The first floor and the mould; Setting of the secund floor [© APDRA-F]
(CIRAD). 100
Photo J. First floor of the monk associated with the pipe (Guinea) [© APDRA-F](CIRAD). 102
Photo K. Top of a monk (DRC)[© Y. Fermon]. 102
Photo L. Building of a pipe(Guinea) [© APDRA-F](CIRAD). 103
Photo M. Setting of a fences with branches (Liberia) [© Y. Fermon]. 108
Photo N. Compost heap. [Liberia © Y. Fermon], [© APDRA-F](CIRAD). 126
Photo O. Use of small beach seine (Liberia, Guinea, DRC) [© Y. Fermon]. 132
Photo P. Mounting, repair and use of gill nets (Kenya, Tanzania) [© Y. Fermon]. 132
Photo Q. Cast net throwing (Kenya, Ghana) [© F. Naneix, © Y. Fermon]. 134
Photo R. Dip net (Guinea) [© Y. Fermon]. 135
Photo S. Traps. Traditionnal trap (Liberia); Grid trap full of tilapia (Ehiopia) [© Y. Fermon]. 136
Photo T. Fish packing in plastic bags (Guinea, (Ehiopia) [© Y. Fermon, © É. Bezault]. 138
Photo U. Hapas in ponds (Ghana) [© É. Bezault]. 143
Photo V. Concrete basins and aquariums (Ghana) [© Y. Fermon]. 145

APPENDIx 187
Photo W. Nests of Tilapia zillii (Liberia) [© Y. Fermon]. 219
Photo X. Claroteidae. Chrysichthys nigrodigitatus [© Planet Catfish]; C. maurus [© Teigler - Fishbase];
Auchenoglanididae. Auchenoglanis occidentalis [© Planet Catfish]. 232
Photo Y. Schilbeidae. Schilbe intermedius [© Luc De Vos]. 233
Photo Z. Mochokidae. Synodontis batensoda [© Mody - Fishbase]; Synodontis schall [© Payne - Fishbase]. 234
Photo AA. Cyprinidae. Barbus altianalis; Labeo victorianus [© Luc De Vos, © FAO (drawings)]. 235
Photo AB. Citharinidae. Citharinus gibbosus; C. citharus [© Luc De Vos]. 235
Photo AC. Distichodontidae. Distichodus rostratus; D. sexfasciatus [© Fishbase]. 236
Photo AD. Channidae. Parachanna obscura (DRC) [© Y. Fermon]. 236
Photo AE. Latidae. Lates niloticus [© Luc De Vos]. 237

xviii Subsistence fishfarming in Africa

Part I
INTRODUCTION AND THEORICAL ASPECTS

Contents
• Fishfarming: Aim and issues
• Type of fishfarming
• Biogeography and fish species
• Summary

Subsistence fishfarming in Africa 1

CONTENTS - PART I

Chapter 01 - FISHFARMING: AIM AND ISSUES 3
I. WHY? 3
II. PRESSURE ON THE RESOURCES 6
II.1. Modifications of the habitat 6
II.2. Water pollution 8
II.3. Fisheries impact 9
II.4. Introductions 9
III. INTERNATIONAL ASPECTS 12
IV. OBJECTIVE OF FISHFARMING 13

Chapter 02 - TYPE OF FISHFARMING 15
I. VARIOUS TYPES OF FISHFARMING 15
II. SOME HISTORY… 17
III. A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE 17
IV. POLYCULTURE VS MONOCULTURE 18

Chapter 03 - BIOGEOGRAPHY AND FISH SPECIES 21
I. GEOGRAPHY 21
II. THE SPECIES 21
I.1. The Cichlidae 22
II.2. The Siluriformes or catfishes 23
II.3. The Cyprinidae 23
II.4. Other families and species 24

SUMMARY 25

Cover photo:
Ö Children fishing fingerlings in river for the ponds, Liberia, ASUR, 2006 - © Yves Fermon

2 Subsistence fishfarming in Africa

Chapter 01
FISHFARMING: AIM AND ISSUES
I. WHY?
Fisheries and aquaculture contribute to the food security primarily in three ways:
Ö To increase the food availabilities,
Ö To provide highly nutritive animal proteins and important trace elements,
Ö To offer employment and incomes which people use to buy of other food products.

A little more than 100 million tons of fish are consumed worldwide each year, and ensure to 2.5
billion of human at least 20% their average needs per capita of animal proteins (Figure 1 below).
This can range to over 50% in the developing countries. In some of the zones most affected by food
insecurity - in Asia and Africa, for example - the fish proteins are essential because, they guarantee a
good part of the already low level of needs of animal proteins. Approximately 97% of the fishermen
live in the developing countries, where fishing is extremely important.
Fish production in Africa has stagnated over the past decade, and availability of fish per capita
decrease (8.8 kg in the 90s, about 7.8 kg in 2001) (Table I, p. 4). Africa is the only continent where this
tendency is observed, and the problem is that there do not exist other sources of proteins accessible
to all. For a continent where food security is so precarious, the situation is alarming.
Even if Africa has the lowest consumption of fish per capita in the world, the marine and inland
water ecosystems are very productive and sustain important fisheries which recorded a rise in some
countries. With a production of 7.5 million tons in 2003 and similar levels in previous years, the fish
ensures 50% or more of the animal protein contributions of many Africans - i.e. the second rank
after Asia. Even in sub-Saharan Africa, the fish ensures nearly 19% of the animal protein contribu-
tions of the population. This constitutes an important contribution in an area afflicted by hunger and
malnutrition.
But whereas the levels of production of fishings are stabilized, the population continues to grow.
With the sight of the forecasts of UN on the population trends and the evaluations available on the

Millions tonnes
140
China
120 World excluding China

100

80

60

40

20

0
50 55 60 65 70 75 80 85 90 95 00 04
Years
Figure 1. World capture and aquaculture production (FAO, 2007).


Table I. World fisheries and aquaculture production and utilization, excluding China
(FAO, 2007).
2000 2001 2002 2003 2004 2005

Production (million tonnes)

Inland Capture 6.6 6.7 6.5 6.6 6.8 7.0

Aquaculture 6.0 6.5 7.0 7.6 8.3 8.8

Total 12.6 13.3 13.5 14.2 15.1 15.8

Marine Capture 72.0 69.8 70.2 67.2 71.3 69.7

Aquaculture 4.9 5.3 5.6 6.1 6.6 6.6

Total 76.9 75.2 75.8 73.3 77.9 76.3

Total Capture 78.6 76.6 76.7 73.8 78.1 76.7

Aquaculture 10.9 11.9 12.6 13.8 14.9 15.4

Total 89.5 88.4 89.3 87.5 93.0 92.1

Utilization

Human consumption 63.9 65.7 65.7 67.5 68.9 69.0

Non-food uses 25.7 22.7 23.7 20.1 24.0 23.1

Population (billions) 4.8 4.9 5.0 5.0 5.1 5.1

Per capita food fish supply (kg) 13.3 13.4 13.3 13.4 13.5 13.4

future tendencies of halieutic production, only to maintain the fish consumption per capita of Africa
on his current levels, the production should increase of more than one third during the 15 next years,
which is a challenge. The situation was partly aggravated by the significant increase in exports, and
harvests of non-African fleets operating in the area under the fisheries agreements.
Fish coastal resources are already heavily exploited and marine capture fisheries would be diffi-
cult to produce more, even through massive investments. Difficult to reduce exports, considering the
need for foreign currencies in the countries concerned.
After a slight downturn in 2002, the total world catch in inland waters is again increase in 2003
and 2004 to reach 9.2 million tonnes during the past year. As previously, Africa and Asia represent
approximately 90 percent of the world total and their respective shares are relatively stable (Figure
2, p. 5). The fisheries, however, seem in crisis in Europe where the total catch has dropped by 30%
since 1999. Game fishing represents a substantial part of the catch. The statistics of developed
countries on catches in inland waters, published by FAO, are generally based on information provi-
ded by national correspondents, and the total catch may vary significantly depending on whether
they take into account or not catch of game fisheries.
In Africa - as in the world in general - aquaculture will play an important role. Globally, aqua-
culture accounts for about 30% of world supplies of fish. The aquacultural production in Africa ac-
counts for only 1.2% of the world total (Figure 3, p. 5). The aquaculture in Africa today is primarily an
activity of subsistence, secondary and part-time, taking place in small-scale farmings.
This African production primarily consists of tilapia (15 000 T), of catfishes (Clarias) (10 000 T)
and of common carps (5 000 T). It is thus about a still embryonic activity and which looks for its way
from the point of view of the development for approximately half a century. The aquaculture yet only
contributes most marginally to the proteins supply of water origin of the African continent where the
total halieutic production (maritime and inland) was evaluated in 1989 to 5.000.000 T. The part of
fish in the proteins supply is there nevertheless very high (23.1%), slightly less than in Asia (between
25.2 and 29.3%), but far ahead of North America (6.5%) or Western Europe (9.4%), world mean of


Oceania 0.2%
North and Central America 2.0%

Europe 3.5%
South America 4.9%

Africa 24.7%
Asia 64.8%

Figure 2. Inland capture fisheries by continent in 2004 (FAO, 2007).

16.5% (Figure 4, p. 6).
Aquaculture in Africa thus remains limited. There are several reasons for this, but the most impor-
tant is that the sector is not treated as a business enterprise, in a viable and profitable point of view.

Quantity

Asia (excluding China) Western Europe 3.54%
and the Pacific 21.92%
Latin America and the Caribbean 2.26%

North America 1.27%
8.51%
Near East and North Africa 0.86%

China 69.57% Central and Eastern Europe 0.42%

Sub-Saharan Africa 0.16%

Value

Asia (excluding China)
and the Pacific 29.30%
Western Europe 7.72%

Latin America and the Caribbean 7.47%

North America 1.86%
19.50%
Near East and North Africa 1.19%

China 51.20% Central and Eastern Europe 0.91%

Sub-Saharan Africa 0.36%

Figure 3. Aquaculture production by regional grouping in 2004 (FAO, 2007).


Fishery food supply (kg/capita)
30

Aquaculture
25
Capture

20

15

10

5

0
70 79 88 97 04 70 79 88 97 04 70 79 88 97 04
World China World excluding China
Years
Figure 4. Relative contribution of aquaculture and capture fisheries to food fish consumption
(FAO, 2007).
But this does not mean ignoring the need for fisheries management. Better management of ma-
rine and inland fisheries in Africa contribute to the safeguarding of these important sectors of food
production. Aquaculture is not intended to replace fishery but to supplement the intake of animal
protein.

II. PRESSURE ON THE RESOURCES
The continental aquatic environments are particularly affected by the human activities: modifica-
tion or disappearance of the habitats generally resulting from water development (dams), pollution of
various origins, overexploitation due to fishing as well as the voluntary or not introductions of non-
native species. The consequences, amplified at the present time by the increase in population and
an increasingly strong pressure on the natural resources, endanger fish fauna quite everywhere in
the world. Long enough saved, Africa suffers in its turn these impacts, even if pollution for example,
remains still relatively limited in space.

II.1. MODIFICATIONS OF THE HABITAT
The alteration of habitat is one of the most important threats to aquatic life. The changes that
may have two distinct origins which generally interfere nevertheless:
9 Climate change with its impact on water balance and hydrological functioning of hydrosys-
tems;
9 The changes due to man both in the aquatic environment and its catchment area.
II.1.1. CLIMATE CHANGES
The existence of the surface aquatic environments depends closely on the contributions due
to the rains, and thus on the climate. Any change in climate will have major consequences in terms
of water balance that will lead by example by extending or reducing aquatic habitat. A spectacular
event is the Lake Chad area of which strongly decreased during the 1970s due to a period of dryness
in the Sahel.
We know that the climate has never been stable on a geological and aquatic environments
have always fluctuated without that man can be held responsible (the phenomenon «El Niño» for
example). But we also know that man can act indirectly on the climate, either locally by deforestation,
or at global level by the emission of certain gases in the «greenhouse effect». These last years, world
opinion has been alerted to a possible warming of the planet which would be due to the increase in
air content of carbon dioxide, methane and chlorofluorocarbons (CFCs), whose emission mass is


linked to industrial activities. If it is not clear to what extent and how fast will this warming, it may be
feared that these climate changes occur in the coming decades, resulting in a change in rainfall in
some regions of the world. Besides small predictable consequences on the water (increase or de-
crease in local rainfall), we can also expect an increase in sunshine and temperature, changes in the
distribution of vegetation, at an elevation sea levels. Although it is still impossible at the local level to
assess the consequences of the changes announced, it seems clear, whatever the magnitude of the
phenomenon that aquatic fauna as a whole will be the first affected..

II.1.2. DEVELOPMENTS
The various uses of water for agriculture, energy production, transport, domestic needs, are at
the base of many hydrological building facilities. These constraints affect the water balance but also,
directly or indirectly, the aquatic habitats.
■ Dams
Large hydroelectric dams are expensive constructions, whose economic interest is often contro-
versial and whose environmental impact is important.
When we block a stream to create a dam, we provoke numerous modifications of the environ-
mental habitat and the fish community and we disrupt the movements of migratory fishes.
■ Development of rivers
The development facilities with the construction of dykes, the rectification of water course, the
construction of locks for navigation ... are still limited in Africa, but we can nevertheless give some
examples of projects that have changed quite considerably natural systems.
In the valley of Senegal, for example, many work was completed for better managing the water
resources of the river and to use them at agricultural ends. The purpose of the construction of a
dam downstream nearby the estuary (dam Diama) is to prevent the coming back of marine water in
the lower course of the river during the dry season, whereas the dam Manantali located upstream
makes it possible to store great quantities of water at the time of the overflood and to restore them
according to the request to irrigate vast perimeters. All the water resources of the valley of Senegal
is now partially under control, but the water management becomes complex to deal with sometimes
conflict demands in term of uses.
■ Reduction of floods plains and wetlands
The wetlands are often considered as fertile areas favourable for agriculture. Everywhere in the
world the development projects and in particular the construction of dams had an significant impact
on the hydrosystems by reducing sometimes considerably the surface of the floodplains which are
places favourable for the development of juveniles of many fish species..
■ Changes in land use of the catchment area
The quantity and the quality of the contributions out of surface water to aquatic ecosystems
depend on the nature of the catchment area and its vegetation. However the disappearance of the
forests, for example, whether to make of them arable lands or for the exploitation of wood for do-
mestic or commercial uses, has, as an immediate consequence, an increase of the soil erosion and
water turbidity, as well as a modification of the hydrological mode with shorter but more brutal runoff
resulting from a more important streaming.
The problem of the deforestation concerns Africa in general and the available information shows
that the phenomenon is worrying by its scale. Thus, it was discovered in Madagascar that the defo-
restation rate was 110 000 ha per year for 35 years, and erosion rate of 250 tonnes of soil per hectare
have been reported. In the Lake Tanganyika drainage, deforestation is massive too. The erosion on
the slopes has resulted in significant contributions to the lake sediment and changes in wildlife in
some coastal areas particularly vulnerable. If current trends continue, the figures are coming with an
estimated worrying that at this rate, 70% of forests in West Africa, 95% of those from East Africa and
30% of the congolese coverage would have to disappear by the year 2040.
The increase in the suspended solid in water, and silt deposits in lakes and rivers, has many ef-
fects on aquatic life. There are, of course, reduce the transparency of its waters with implications for
the planktonic and benthic photosynthesis. The suspension elements may seal the branchial system
of fish or cause irritation and muddy deposits deteriorate the quality of substrates in breeding areas.


II.2. WATER POLLUTION
If water pollution has long appeared as a somewhat secondary phenomenon in Africa, it is clear
that it is increasingly apparent in recent years. In general, however, lack of data and more detailed
information on the extent of water pollution in Africa.
II.2.1. EUTROPHICATION OF WATER
The nutritive elements (phosphates, nitrates) are in general present in limited quantities in the
aquatic environments, and constitute what one calls limiting factors. Any additional contribution of
these elements is quickly assimilated and stimulates the primary production. When the natural cycle
is disturbed by the human activities, in particular by the contributions in manure, detergents, waste
water in general, excesses of phosphates (and to a lesser extent of nitrates) is responsible for the
phenomenon of eutrophication. This phenomenon results in an excessive proliferation of algae and/
or macrophytes, and a reduction in the water transparency. The decomposition of this abundant
organic matter consumes much oxygen and generally leads to massive mortalities of animal species
per asphyxiation. Eutrophication also has as a result to involve strong variations of the dissolved
oxygen concentration and pH during the day. In the lakes, the phenomenon of “bloom” (the “fleur
d’eau” of the French speaking) is one of the manifestations of eutrophication.
Eutrophication of Lake Victoria during the last 25 years is fairly well documented. Increased
intakes of nutrients to the lake is the result of increasing human activities in the catchment area of
the lake: increased urbanization, use of fertilizers and pesticides for the crops, use of pesticides for
control of tsetse flies ...
II.2.2. PESTICIDES
In the second half of the twentieth century the use of chemical pesticides has become wides-
pread in Africa, as elsewhere in the world to fight against both the vectors of major diseases and
pests of crops. The range of products used is very large and, if some have a low toxicity towards
aquatic organisms, many are xenobiotics, ie substances that have toxic properties, even if they
are present in the environment at very low concentrations. This is particularly true for pyrethroids
(permethrin, deltamethrin) but especially for organochlorines (DDT, dieldrin, endrin, endosulfan, ma-
lathion, lindane), which, in addition to their toxicities have important time remanence, this which
accentuates their accumulation and thus their concentration in food webs.
II.2.3. HEAVY METALS
Under the term of “heavy metals”, one generally includes several families of substances:
9 Heavy metals in the strict sense, with high atomic mass and high toxicity, whose presence in
small amounts is not necessary to life: cadmium, mercury, lead…
9 Metals lower atomic mass, essential for life (trace elements), but quickly become toxic when
their concentration increases: copper, zinc, molybdenum, manganese, cobalt…
Heavy metals usually occur at very low concentrations in natural ecosystems but human activi-
ties are a major source of pollution. Heavy metals come from the agricultural land and water systems
by intentional inputs of trace elements and pesticides, discharge from refineries or factories treating
non-ferrous metals (nickel, copper, zinc, lead, chromium, cadmium ...), discharges from tanneries
(cadmium, chromium) or paper pulp (mercury). It must be added the impact of atmospheric pollution
related to human activities (including industrial), and domestic and urban effluents (zinc, copper,
lead). Mercury pollution may have originated in industrial uses (paper industry), the exploitation of
gold deposits, the use of organomercury fungicides. The problems associated with heavy metal
contamination resulting from the fact that they accumulate in the organisms where they may reach
toxic levels.
II.2.4. BIO-ACCUMULATION
An alarming phenomenon with certain contaminants, including heavy metals or pesticides, is the
problem of bioaccumulation which leads to the accumulation of a toxic substance in an organism,
sometimes in concentrations much higher than those observed in the natural environment. This
concerns various contaminants.


Organisms with concentrated pollutants can enter to turn the trophic chain, and if the product
is not degraded or removed, it will concentrate more and more with each trophic chain link, eg from
algae to ichthyophagous birds. This phenomenon which is called biomagnification, shows that the
pollution of environment by substances that are measured in very small quantities in water, can have
unexpected consequences on higher consumer.

II.3. FISHERIES IMPACT
The impact of fishing on fish populations appears primarily, according to the fishing gears used,
by a selective pressure on certain species, either on adults, or on juveniles. It is frequently thought
that fishing alone, when used with traditional gear, can not be held responsible for the disappearance
of fish species. Indeed, it is not easily conceivable that one can completely eliminate a population
by captures made as a blind man contrary with what can occur for hunting. However, a pressure
associated with changes in habitat can lead fairly rapidly declining species.
The effects of fishing are particularly sensitive to large species with low reproductive capacity.
One quotes for example the quasi-disappearance of the catfish Arius gigas in the basin of Niger. In
this species, the male is buccal incubator of a few large eggs. In the early 20th century, it referred to
the capture of specimens of 2 meters long, while since 1950 the species seemed to become very
rare.
One of the clearest fishing effect is showned in the population demography, with the reduction
in the mean size of species and the disappearance of large individuals. Indeed, if the fishery usually
starts with large gear mesh, the size of these decreases as catches of large individuals are rare.
In some cases, the mesh size is so small that gear catch immature individuals and populations of
species that can not reproduce collapsing dramatically. In the lake Malombe for example, the fishing
of Oreochromis (O. karongae, O. squamipinnis) was done with gillnets. It has been observed in the
1980s increased fishing with small mesh seines, and a parallel collapse of the Oreochromis fishery.
This mode of exploitation would be responsible also for the disappearance of nine endemic species
of large size of Cichlidae.

II.4. INTRODUCTIONS
While for centuries introductions of fish species have been promoted across the world to improve
fish production, they have become in recent decades the subject of controversy among scientists
and managers of aquatic environments. Indeed, the introduction of new species can have significant
effects on indigenous fish populations.
The introduction of new species in an ecosystem is sometimes the cause of the phenomena of
competition that may lead to the elimination of native species or introduced species. But there may
also have indirect changes, which are generally less easy to observe, through the trophic chains.
To correctly interpret the impacts of introductions, it is necessary to distinguish several levels from
intervention:
9 That of the transplantation of species of a point to another of the same catchment area;
9 That of the introduction of alien species to the basin but coming from the same biogeogra-
phic zone;
9 That of the introduction of species coming from different biogeographic zones, even from
different continents.
II.4.1. COMPETITION WITH THE INDIGENOUS SPECIES
Introduced species may compete with native species, and possibly eliminate them. This is es-
pecially true when introducing predator species. One of the most spectacular cases is that of the
introduction into Lake Victoria of the Nile Perch, Lates niloticus, a piscivorous fish being able to reach
more than 100 kg. To some scientists, this predator is the cause of the decline and likely extinction
of several species belonging to a rich endemic fauna of small Cichlidae which he fed on.
`


II.4.2. EFFECT ON AQUATIC ECOSYSTEM
The introduction of a predator in an aquatic ecosystem can affect the biological functioning of
the system through the trophic chains. Using the example of Lake Victoria, the Nile perch would be
responsible for the virtual disappearance in the 80s of the group of detritivores / phytoplanctivore of
haplochromine (Cichlidae endemic), and the group zooplanctivores which were respectively 40 and
16% of the biomass of demersal fish. Detritivorous have been replaced by indigenous shrimp Cari-
dina nilotica, and by the zooplanctivores Cyprinidae pelagic Rastrineobola argentea, these latter two
species have become the mean food of the Nile perch after the disappearance of the haplochromine.
II.4.3. HYBRIDIZATIONS
The introduction into the same water body of related species that do not normally live together
may result in hybridization. Species of tilapia, in particular, are known to hybridize, which can cause
genetic changes for the species surviving. For example, in Lake Naivasha, Oreochromis spilurus in-
troduced in 1925 was abundant in the years 1950 and 1960, and then hybridize with O. leucostictus
introduced in 1956. This resulted in the disappearance of O. spilurus and hybrids. The disappea-
rance of the species O. esculentus and O. variabilis, endemic to Lakes Victoria and Kyoga, could
be due to hybridization and/or competition with introduced species (O. niloticus, T. zillii). Hybrids
O. niloticus x O. variabilis were found in Lake Victoria.
If we consider the introductions and movements of fish in Africa, everything and anything has
been done (Annexe 02, p. 197, Table II, p. 10 and Table III, p. 11). First by the colonialists who introduced
the species they used as trout or carp. Then many species have been transplanted from country to
country in Africa to test for fishfarming, as many tilapia. This up to nonsense as to bring strains of
Nile Tilapia (Oreochromis niloticus niloticus) or Mossambic Tilapia (O. mossambicus) in areas where
there were native strains. For example, the famous strain of “Bouaké” in Ivory Coast which would
be, in fact, a mixt of several broodstocks, was introduced into several countries in which the species
O. niloticus is native. Same thing on the strain of Butaré, in Rwanda, where it would seem that it is
a stock brought back the first time to the United States by a research institute and brought back
afterwards to Rwanda!! (Lazard, pers. com.).
Elements are given on the distribution of the species in Appendix 05, p. 255.

Ö In this case, it is to pay attention to the provenance of the fish to use and watershed
where action is taken, more so, because of the risks incurred by the introduction of fish and
national and international legislative aspects concerning biodiversity..
Ö This is not because a species has already been introduced in the intervention area, that
it is necessary to use it.

Table II. Origin and number of fish species introductions in Africa.
Coming from Number
Africa 206
North America 41
South America 3
Asia 58
Europe 92
Unknown 128
Total 528


Table III. Introduced species with a negative ecological effect recorded.
ENE= Number of country which have recorded an Ecological Negative Effect.
French common English common ENE
Order Family Species (n = 39) name name
Sardine du Tanga- Lake Tanganyika
Clupeiformes Clupeidae Limnothrissa miodon 3
nyika sardine
Amour marbré, à
Cypriniformes Cyrpinidae Aristichthys nobilis Bighead carp 3
grosse tête
Carassius auratus auratus Poisson rouge Goldfish 9
Carassius gibelio Carpe de Prusse Prussian carp 4
Ctenopharyngodon idella Carpe herbivore Grass carp 5
Cyprinus carpio carpio Carpe commune Common carp 22
Hemiculter leucisculus Vairon Sharpbelly 3
Hypophthalmichthys molitrix Carpe argentée Silver carp 9
Pimephales promelas Tête de boule Fathead minnow 3
Pseudorasbora parva Pseudorasbora Stone moroko 12
Siluriformes Ictaluridae Ameiurus melas Poisson chat Black bullhead 8
Ameiurus nebulosus Poisson chat Brown bullhead 3
Poisson chat mar-
Clariidae Clarias batrachus Walking catfish 5
cheur

Clarias gariepinus Poisson chat nord North African 6
africain catfish
Vermiculated
Loricariidae Pterygoplichthys disjunctivus Pléco 3
sailfin catfish
Esociformes Esocidae Esox lucius Brochet Northern pike 5
Salmoniformes Salmonidae Oncorhynchus mykiss Truite arc-en-ciel Rainbow trout 21
Salmo trutta trutta Truite de mer Sea trout 12
Salvelinus fontinalis Saumon de fontaine Brook trout 5
Atheriniformes Atherinopsidae Odontesthes bonariensis Athérine d’Argentine Pejerrey 4
Cyprinodontiformes Poeciliidae Gambusia affinis Gambusie Mosquitofish 9
Poecilia latipinna Molly Sailfin molly 3
Poecilia reticulata Guppy Guppy 8
Xiphophorus hellerii Porte-épée vert Green swordtail 4
Grémille, Goujon-
Perciformes Percidae Gymnocephalus cernuus Ruffe 3
perche
Perca fluviatilis Perche commune European perch 3
Centrarchidae Lepomis gibbosus Perche soleil Pumpkinseed 9
Lepomis macrochirus Crapet arlequin Bluegill 6
Black-bass à petite
Micropterus dolomieu Smallmouth bass 3
bouche
Black-bass à grande
Micropterus salmoides Largemouth bass 13
bouche
Gobiidae Neogobius melanostomus Gobie à taches noires Round goby 6
Odontobutidae Perccottus glenii Dromeur chinois Chinese sleeper 4
Latidae Lates niloticus Perche du Nil Nile perch 4
Tilapia du Mozam- Mozambique
Cichlidae Oreochromis mossambicus 21
bique tilapia
Oreochromis niloticus niloticus Tilapia du Nil Nile tilapia 16
Parachromis managuensis Cichlidé de Managua Guapote tigre 3
Sarotherodon melanotheron Tilapia à gorge noire Blackchin tilapia 3
melanotheron
Tilapia rendalli Tilapia à ventre rouge Redbreast tilapia 3
Tilapia zillii Tilapia à ventre rouge Redbelly tilapia 3


III. INTERNATIONAL ASPECTS
The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention,
is an international treaty that was adopted at the Earth Summit in Rio de Janeiro in June 1992. The
Convention has three main goals:
1. Conservation of biological diversity (or biodiversity);
2. Sustainable use of its components;
3. Fair and equitable sharing of benefits arising from genetic resources.

In other words, its objective is to develop national strategies for the conservation and sustai-
nable use of biological diversity. It is often seen as the key document regarding sustainable deve-
lopment.The Convention was opened for signature on 5 June 1992 and entered into force on 29
December 1993. It has been signed in December 1993 by 168 countries. Somalia is the only of the
53 African countries which have not signed.
The convention recognized for the first time in international law that the conservation of bio-
logical diversity is «a common concern of humankind» and is an integral part of the development
process. The agreement covers all ecosystems, species, and genetic resources. It links traditional
conservation efforts to the economic goal of using biological resources sustainably.
At the meeting in Buenos Aires in 1996, the focus was on the local knowledge. Key actors, such
as local communities and indigenous peoples, must be taken into account by the States, which
retain their sovereignty over the biodiversity of their territories they must protect. It establishes the
principles for the fair and equitable sharing of benefits arising from the use of genetic resources,
including those intended for commercial use. It also covers the area of biotechnology through its
Cartagena Protocol on Biosafety in 2001, addressing issues of technological development, benefit-
sharing and biosafety.
The convention reminds decision-makers that natural resources are not infinite and sets out a
philosophy of sustainable use. While past conservation efforts were aimed at protecting particular
species and habitats, the Convention recognizes that ecosystems, species and genes must be used
for the benefit of humans. However, this should be done in a way and at a rate that does not lead to
the long-term decline of biological diversity.

Ö Above all, the Convention is legally compulsory, the member states are forced to im-
plement its mesures.
Ö This means to respect these mesures in the projects on the field while avoiding up to
have an effect on the environment that may affect biodiversity. If so, this could turn against
the organism responsible for the project despite the intentions and the tacit agreement of
local and regional authorities.


IV. OBJECTIVE OF FISHFARMING
It is not necessary that pisciculture is made at the expense of the natural environments. A fishfar-
ming causing of the organic matter rejections or being implied in the introduction of an alien species,
can involve an important ecological change and, therefore, to have serious effects on the animal
protein contribution. Indeed, there exists a big risk of reduction of the captures of fishings whereas
fishfarming is made for an additional contribution, not for a replacement of the available re-
source, in the case, of course, where this one is present.
As shown in the Figure 5, p. 14, in addition to the strictly desert zones, where, for lack of water,
fishfarming can be difficult, it is possible to produce fish almost everywhere in Africa.

Ö The objective of the fishfarming is not to replace fisheries but to supplement its contri-
butions in maintaining the current level of fish consumption, regarding the increase of
world population. However, this goal must be pursued in respect of environmental, consu-
mer health and bioethics.


Constraint
Unsuitable
Moderatly suitable
Suitable
Very suitable
No data

Figure 5. GIS assessment of potential areas for production fish farms in Africa.


Chapter 02
TYPE OF FISHFARMING
According to FAO (1997), aquaculture is defined as:
« The culture of aquatic organisms including fish, molluscs, crustaceans and aquatic plants. The
term culture implies some form of intervention in the rearing process to enhance production, such
as restocking at regular intervals, food, protection against predators ... This culture also implies indi-
vidual or legal ownership of the breeding stock. From the viewpoint of statistics, aquatic organisms
harvested by an individual or legal person who had owned throughout their breeding period are
products of aquaculture. On the other hand, publicly aquatic organisms used as a common property
resource, with or without appropriate licenses are to be considered as fishery products »
In this case, we are interested in the culture of fishes or fishfarming.

I. VARIOUS TYPES OF FISHFARMING
The types of fishfarming depend mainly on the investment, the quantity of fish produced per unit
of area and on the destination of the products. They are generally characterized by their degree of
intensification, itself definite according to the feeding practices; the external food supply represents
indeed in general more than 50% of the total costs of production in the intensive systems. However
the intensification involves many other factors of production, like water, land, capital and labor.
The various types of systems of fish production are presented in Table IV, p. 16 according to their
degree of intensification. A first classification can be established in the following way:
9 Extensive fishfarming systems, based on the natural productivity of the pond or on the
structure of farming, without or with very few inputs. Generally, there are farming installed in basins
or medium or large ponds. Food is quite simply provided by the natural productivity of the water,
which is very little or slightly favourably increase. The external contributions are limited, the costs
remain weak, the funded capital is reduced, the quantities of fish produced per unit of area are low.
In short, the control of the factors of production remains on a low level. The systems of integration of
rice and fishfarming belong to this extensive category, since the fish profits from the inputs brought
for the culture of rice.
9 Semi-intensive fishfarming systems are based on the use of a fertilization or the use of a
complementary food, knowing that a large part of the food of fish is provided in situ by natural food.
The farming associated with poultry-fish or pig-fish belong typically to this type of fishfarming.
9 Superintensive and intensive systems and, in which all the nutritional needs for fish are
satisfied by the inputs, with small or very few nutritional contributions resulting from the natural
productivity from the basin or the water in which the fish is produce (lake, river). The food used in
these systems of farming is generally rich in proteins (25 to 40 %); it is consequently expensive.
The intensive fishfarming means that the quantities of fish produced per unit of area are high. To
intensify the farming and to improve the conditions, the factors of production (food, water quality,
quality of fingerlings) must be controlled. The cycle of production requires a permanent follow-up.
The principal infrastructures of this type of fishfarming the enclosures or the cages, with very high
renewal rates of water.
The evolution of an extensive system to an intensive system which are the two extremes, is lin-
ked to the evolving global investment from low to important.
Another typology of fish production systems can be proposed, based on a differentiation
between:
9 The models where the food is coming essentially (or only) from the ecosystem (case of the
ecosystem pond), systems called production fishfarming. The management of this type involves the
fertilization or the complementary food, with the implementation of the polyculture. There is a strong
interaction between the density of fish, the final individual weight of fish (growth rate) and the perfor-
mance which must be managed carefully. It is thus a question of recreating an ecosystem where the


Table IV. Different levels of intensification of fishfarming systems.
Density of fish at
< 0.1 m-2 0.1 to 1 m-2 1 to 5 m-2 5 to 10 m-2 10 to 100 m-2
stocking
Pond, small dam, Ponds, pools,
Farming structure Pond Pond, cage
pool raceways, cages
Yield 50 and more to
0 - 0.3 0.3 - 1 1 to 5 5 to 15 15 to 50
(t/ha/year) 200 kg.m-3
Generally,
Fish intitial stock Mainly polyculture Polyculture Monoculture
monoculture
Fertilizers, macrophytes, Equilibrate food with
Inputs Low or no inputs simple food (bran, Composed food fish meal, extruded,
oilcake) antibiotic

Compensation for Ventilation,
Naturel contribution Ventilation/oxygenation
Dayly rate of water losses water circulation
renewal (%)
Sometimes
None <5 5 to 30 > 30
<5
Intensification level Extensive Semi-intensive Intensive Super intensive

Models Semi-fishfarm Production fishfarm Transformation fishfarm

fish are at the end of the trophic chain.
9 The models where the food is entirely exogenous and that the fish feeds entirely with artificial
food, usually in the form of granules and having a very high proportion of fishmeal, systems called
transformation fishfarming. The management of this second type is primarily based on monocul-
ture, of the high densities of fish and an artificial food rich in proteins.
The decision to implement one of these types of fishfarming depends on many factors which are
presented in Table V, p. 17.
Another typology of African piscicultures resulted in classifying them in four categories, on the
basis of socio-economic criterion and not of the level of intensification of the production:
9 The subsistence or self-consumption farming (of which the product is for the provisioning
of the fishfarmer and his family), where the techniques implemented, qualified as extensive ones,
correspond to a low level of technicality.
9 The artisanal or small scale fishfarming, which develops primarily in suburban zone and
which offers the best environment for the supply of inputs and the marketing of fish.
9 The fishfarming of the type “channel” characterized by the segmentation of the various
phases of farming, mainly in cages and enclosure.
9 The industrial fishfarming, characterized by production units of great dimension whose ob-
jective is strictly economic, even financial, in opposition to the three preceding forms where fishfar-
ming constitutes not only production tools, but also development tools.
For a long time it was allowed that the practice of production fisfharming required only one low
level of technicality on behalf of the fishfarmers compared to system baseds on an exogenic food.
Reality is not that simple.
The intensive fishfarming models, based on advanced technologies, are ultimately perhaps ea-
sier to transfer as their main components are well defined and that the farmer is led in an environment
where the not controlled natural components interfere little (farmer in cages in lakes and rivers) or at
all (raceways, vats). The production costs and the outputs are higher in the intensive systems. But
there exist important obstacles, in any case initially:
¾ The level of risk, in terms of diseases of fish, is important in the intensive systems compared to
the extensive systems,
¾ The starting investment is very high and is productive only after several years, which implies,
¾ Training of technicians and that takes time with the professionalism,


Table V. Characteristics of the two main models of farming towards the various factors of
production. The symbol – means that the production factor is a constraint for the establishment of the
fishfarming involved; the symbol + an asset.
Production factor Transformation fishfarming Production fishfarming
Land + –
Water discharge surface
Environnemental impact – +
Working capital – +
Labor force
+ +
(per kg of produced fish)
«Food» – +
Technicity – –
Risk – +
Production costs – +
Yield + –
Plasticity
(ex: Juveniles production) – +

¾ The establishment of a chain of sale must be accompanied by a fish processing and other
ways of preservation and transport.
In this context, the concepts of intensive and extensive take a particular significance. Thus, the
fish industry, a long time regarded as a way of geographically concentrated production factors and
to achieve economies of scale is generally comparable with the intensive concept and privatization
seems that he could not pass through it. It now appears that all such projects implemented so far
on the African continent, have failed from their original purpose, ie to produce a fish at a lower cost
price sale.
It will thus be a question of establishing a system of production and of marketing of the produc-
tion, which requires as first, a good feasibility study. This is excluded in zones where the demand for
animal proteins must be rather fast because of a lack for the populations. On the other hand, this
type of system can be developed after a first intervention of the production type.

II. SOME HISTORY…
Although it was shown that the tilapia Oreochromis niloticus was rise in ponds by the Egyptians,
there are nearly 4 000 years, the fact remains that the African continent, unlike Asia, has no tradition
in fishfarming. At the beginning of the century, aquaculture was still totally unknown on the conti-
nent. The initial studies on tilapia date from the nineteenth century and the first attempts to develop
aquaculture dates back to the 1940s.
The attempts to introduce aquaculture in Africa around 1950, were for diversification of sources
of animal protein to promote food self-sufficiency of rural populations. The first tests performed
with tilapia in the station Kipopo established in 1949 (former Belgian Congo) have yielded promising
results, the colonial government began outreach. In 1957 the station of Kokondekro near Bouaké in
Côte d’Ivoire was created for the purpose of research and training. The first tests were carried on
species now abandoned because of poor performance in intensive: Tilapia zillii, Tilapia rendalli and
Oreochromis macrochir. It was not until the 1970s that it was found that the zootechnical perfor-
mance of Oreochromis niloticus (formerly Tilapia nilotica) significantly exceeded those of most other
tilapia. It is also from this period that one began to focus on the identification of other species of fish
in Africa with high potential for aquaculture. But despite a massive help to promote family farming,
like Asia, the results were disappointing.

III. A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE
In the framework of humanitarian NGOs, it is above all to enable people to have animal protein
at a lower cost and within a short time.
So a fishfarm in extensive to semi-intensive, of production, requiring minimal technical to be


easily reproducible will be preferable. This, while producing in a rather short time a quantity of fish
of consumable size. In many countries, fish from 80 to 100 g are consumed. It will thus not be a
question of producing fish of 300 g or more, which takes a more important time. It is a fishfarming of
self-consumption but artisanal.
Important points:
9 Minimum of technique for a good appropriation by the beneficiaries,
9 Reduced impact on the environmental context: local species,
9 Fast production with lower costs,
9 Minimum of intervention on the ponds by the beneficiaries who have other major activities,
9 Minimum of inputs: alive or material.
9 Potentialities of Incomes Generating Activities (IGA): according to the size of the fishfarming
and the number of ponds, one can arrive at a system allowing a IGA with use of people for the current
maintenance and care on the ponds, while keeping an extensive system of production, because of
technicality requested.
The extensive fishfarming suggests a minimal action of man, with a prevalent contribution of the
natural environment which one will seek to develop as well as possible. This practice is common in
rural areas of the poor countries, where the level of average richness of the small producers does not
allow them to acquire external inputs to the system.
The meaning of the “extensive” character of the aquiculture is perceived paradoxically only com-
pared to its degree of intensification, i.e. on the level growing of the intervention of the producer in
the life cycle of the water orgaisms (Table IV, p. 16). It results from this an increase in investments and
production costs while evolving of extensive to the intensive (Figure 6, p. 19). Collection of animal
material (larvae, juveniles or subadults) into the wild, and its farming in captivity until a marketable
size by using the techniques of farming constitutes the fishfarming based on fishery. These kinds of
semi-fishfarm practices include the fishfarming on low level of inputs, practiced by the majority of
the small fishfarmers of sub-Saharan Africa. It is based on the valorization of space by the fishfarm
installation of the shallows in forest zone. The social aspects take more importance here, especially
in the community management of the amplified fisheries. The fishfarming, in this case, makes it pos-
sible to bring a protein complement “fish”, that cannot only be provide by fishery. The association of
the two systems, when they are present, also reduced pressure on the fishing resources.
In terms of land needs, for a level of given production, the ponds require more land surface (or
surfaces of water) that more intensive systems which, them, require high renewal rates of water. The
fish ponds in general have a weak negative impact on the environment, except in the case of use
of exotic species whose escape in natural environment can appear catastrophic. The ponds can be
used to recycle various types of waste like the effluents (domestic or of livestocks), in environments
directly or indirectly via stocked watershed stabilization and maturation (pond) where fish is the
ultimate link.
It is thus this approach which will be privileged within the framework of this handbook.

IV. POLYCULTURE VS MONOCULTURE
Monoculture is the principle of using only one species in production in the fishfarm structures.
The logic of polyculture is similar to the logic of crops. The association of fish with different diets
increase the net yield and value of production. Polyculture allow an intensification of production per
unit area, for against, it often leads to a decrease in the value of work. The principle used in a subsis-
tence pond is to recreate a semi-natural ecosystem turning on itself. This is an intermediate situation
between monoculture, where the flow of energy is concentrated on one species and a natural ba-
lance in which the beneficiaries of the flow are very diverse in terms of species. The target species
are generally species at the bottom of the trophic chain, with a tendency to reproduce at small sizes.
It is therefore to put other species, as predators, to control the population and ensure that fish are
investing more in growth than in reproduction.
In Africa, fish farms combine tilapia (often of the Nile, Oreochromis niloticus) as a main species
with a Siluriformes (Heterobranchus isopterus, Clarias spp.), a Arapaimidae (Heterotis niloticus) and
the predator Hemichromis fasciatus (to remove the unwanted fry) . In these conditions the secondary


Investment
Super-intensive Deep-sea fishery

Intensive Coastal fishery

Semi-intensive Artisanal fishery

Extensive Pond, wetland

Aquaculture Fishery
Figure 6. Continuum Aquaculture - Fishery en relation with the investment intensification.
(Mikolasec, 2008, under press)

species may increase the total fish yield of over 40%. Whatever the species of tilapia used, with the
increase in the number of age classes in an farm enclosure, competition leads rapidly to prevent a
good growth of first stocked fish.
The association of a predator to the farming of tilapia to control the undesirable reproduction of it
is carried out today by a growing number of African fishfarmers. Within this framework, Siluriformes
(Clarias or Heterobranchus sp.) are often regarded as having a double function: predation and poly-
culture. Associated results of farming Clarias - Tilapia show that a big number of individuals of Clarias
is necessary to the total control of the reproduction of O. niloticus and that they exert a competition
with respect to the food resources available in the pond. To control a population of 1200 tilapia in
pond of 10 ares, a population of 260 Clarias of initial mean weight higher than 150 g is necessary
and the growth of the tilapia is lower than that of an identical farming in which Clarias is replaced by
a strict predator (Hemichromis fasciatus). It was also noted that, in the presence of a predator, the
tilapia tend to invest in the growth before reproducing, which could be related to the fact that they
can then better ensure the defense of their youngs.
There exist various advantages to polyculture:
9 The natural foods are used better, in a more complete way, since only one species, even
with a broad food spectrum, never uses all the food resources of a pond.
9 Certain trophic dead ends are avoided. The fish do not consume all the organisms as cer-
tain small crustaceans which can develop in the ponds. It is a question of controlling the populations
of this invader by introducing a species which either will reduce the food of the intruder, or to feed
itself directly on the intruder.
9 The production of natural foods is stimulated. The fish with digger behavior when they
are in the search of food can suspend particles and, thus, aerate the sediment, to oxidize the organic


matter and to improve recycling of the nutritive elements which stimulate the production of natural
foods.
9 There can be a double fertilization. The dejections of herbivorous fish are so much “rich”
that they have a fertilizing impact which can be compared with that of an associated terrestrial
farming. This effect is sometimes named “double fertilization” because a chemical fertilization is
much more effective when these fish are present in the mixed-farming. For example, this double
fertilization can increase the carp yield from 14 to 35% compared to a normal fertilization obtained
in pond of monoculture.
9 Water quality is improved. In pond, the presence of tilapia makes it possible to improve
oxygenation of water. The tilapia improve also oxygenation by consuming the organic matter of the
bottom which, if not, would have been mineralized by the bacteria consuming oxygen.
9 The organisms are better controlled. . The control of molluscs is possible in ponds while
using Heterotis niloticus, whereas the proliferations of small wild fish or shrimps can beings control-
led by using carnivorous fish.

There exist also disadvantages with the polyculture which occur especially when an imbalance
appears following a competition between the species. Moreover, when the fish density is very high,
the role of the natural productivity of the pond in the diet of fish decreases, since the natural trophic
resources must be allocated among all the individuals. The profit obtained by the practice of the
polyculture is relatively limited, whereas the work caused by the sorting of the various species at the
time of harvest becomes a real constraint.
Monoculture is thus the only method of farming used in the intensive systems where the contri-
bution of natural foods is very limited. In pond, high densities of fish are not current, because the
oxygenation and the accumulation of toxic substances (ammonium, nitrites…) quickly become a
limiting factor.

Ö We therefore choose a fishfarming system of production, semi-intensive, of self-
consumption to artisanal, using polyculture rather than monoculture that request external
food input and a more important follow-up if we want an interesting production.


Chapter 03
BIOGEOGRAPHY AND FISH SPECIES
I. GEOGRAPHY
The fish faunas were established and have evolved according to the history of aquatic systems
they occupy. They are far from being homogeneous for the whole of Africa.
The existence and survival of aquatic habitats depend on two main factors: their morphology,
which can be modified on the long term by erosion or tectonic; hydrological balance which depends
on precipitation, evaporation, and infiltration, and for which small changes can lead to short or me-
dium term to the drying or to the expansion of the aquatic environment considered, according to the
shape of the basin. Communications can then be created between different basins. At various time
scales, some basins have been colonized from other basins, and those colonizations have some-
times been followed by selective extinctions resulting from climatic and / or geological events. Si-
multaneously, some species were able to evolve to other species, and these speciation phenomena
explain often the presence of areas of endemism.
The African continent can be separate in several great ichthyologic regions or ichthyoregions
(Figure 7, p. 22). They were defined according to affinities between fish faunas. Each region includes
several catchment areas of different size. For example, the soudano-nilotic region includes several
large basins like the Nile, Niger, Senegal.
The political divison of the countries does not correspond little or not to the ichthyoregions. A
country either is included completely in only one ichtyoregion, or with overlap on several. One will
find in Annex 04, the Table XLVI, p. 246 which indicates for each African country the ichthyoregions
of which its area forms part and in the Table XLIV, p. 240 of geographical information for each African
country.

Ö It will be necessary to check in which country the intervention must take place and see
the corresponding ichthyoregion. Then one can refer in the Annex, on the various tables
for the species which may probably be used in aquaculture, particularly tilapia.

II. THE SPECIES
Among the 292 farmed species listed by the statistics of FAO (1995) and for which data are
available, the first 22 species represent 80 % of the total production. Among these 22 species, prac-
tically all the species are filterers, herbivorous, or omnivorous. Only one species, the Atlantic salmon,
is carnivorous and it is clearly about a minor species in terms of volume of production. The most
important group is that of fresh water fish: 12,7 million tons, in comparison with 1,4 million tons for
amphihalins fish and 0,6 million tons for marine fish.
The fresh water fish are dominated by Cyprinidae (carps) and Cichlidae (tilapia). Cyprinidae pre-
sent a certain number of comparative advantages: they can use food with proteins and fish meal
contents limited; they can beings raised in polyculture, allowing an optimal valorization of the natural
productivity of the ponds and water pools in which they are stored; they also correspond to growth
markets in the Asian countries, because of the traditions and the relatively low prices.
For Africa, the aquacultural production remains mainly on two groups of indigenous species: the
tilapia (12 000 tons annual) and the catfishes (7 000 tons), and of the introduced species of which
the carps (2 000 tons). Historically in fact the tilapia were the subject of the first work of aquacultural
experimentation in Africa, mainly in DRC (ex-Zaire) and in Congo, in particular because of their easy
reproduction in captivity. Thereafter, various species were tested in order to determine their fishfar-
ming potentialities. Thus, at the beginning of the year 1970, in Central African Republic, the high
potential of the catfish Clarias gariepinus on which important research tasks were undertaken, have
been put forward. Then in the years 1980, other species of fishfarming interest were identified, in


Mediterranean Sea

Red Sea

Indian
Ocean

Atlantic Ocean

Figure 7. The ichthyoregions (limits in yellow-green) and the countries (limits in red)
(Faunafri).
particular in Ivory Coast, on the basis of their appreciation by the zootechnical consumers and their
performances. The biological cycle of some of them is now completely controlled, which allowed the
starter of their fishfarming production.

II.1. THE CICHLIDAE
In Africa, the species mainly used in fishfarming are fish of the family of Cichlidae, group of Tila-
piines. They are commonly called tilapia and are mainly herbivorous / microphagous. They practice
parental care. Called “water chickens”, tilapia have biological characteristics particularly interesting
for fishfarming:
9 They have a good growth rate even with a food containing few proteins;I
9 They tolerate a broad range of environmental conditions (oxygenation, salinity of water…);
9 They reproduce easily in captivity and are not very sensitive to handling;
9 They are very resistant to the parasitic diseases and infections;


9 They are appreciated by consumers.
We know more than a hundred species of «tilapia» described. More than 20 species have been
recorded in some countries (Annexe 04 p. 239). Some are endemic of lakes or very circumscribed
zones. The maximum size observed is very variable and does not reach more than 5 cm until more
than 60 cm Total Length (TL). The species of Tilapiines are separate in various genera whose the 3
principal ones are Oreochromis, Sarotherodon and Tilapia. This separation in genera is mainly related
to the mode of reproduction of these species. Oreochromis are maternal mouthbreeders, i.e. the fe-
males keep the eggs and juveniles in their mouth to protect them. The fish of the genus Sarotherodon
are also mouthbreeders, but biparental, the two parents can incubate. The fish of the genus Tilapia
are substrate spawners. The maximum growth obtained is of 3 grams per day.
Oreochromis niloticus was one of the first to being cultivated, and remains the most common
species. But many other species were also used: O. aureus, O. macrochir, O. mossambicus, Tilapia
rendalli, T. guineensis, Sarotherodon melanotheron. This last, frequent in the estuariens and lagu-
naires western African ecosystems, appears more particularly adapted to a brackish water farming.
Many of these species are now widespread in the whole world, either that they were introduced
into natural environments to improve fishing, or which they are used as a basis for the fishfarming
production.
Between 1984 and 1995, the contribution of the tilapia of fishfarming to the total production of
tilapia passed from 38 % (198 000 t) to 57 % (659 000 t). Four species or groups of species domina-
ted the production between 1984 and 1995, where they contributed for 99.5 % to the production of
all Cichlidae. The Nile tilapia represented 72 % of the total production of tilapia; the annual growth
rate of its production between 1984 and 1995 was of 19 %. In 1995, the principal producers of tilapia
were China (315 000 t), Philippines (81 000 t), Indonesia (78 000 t) and Thailand (76 000 t)!
Other Cichlidae were used in order to control the populations of tilapia in the ponds. They are
predatory species of the kinds Serranochromis and Hemichromis.

II.2. THE SILURIFORMES OR CATFISHES
Siluriformes are, in fact, the catfishes. They are separate in several families.
The interest in fishfarming of African species is recent. Some species of Siluriformes are very
interesting for fishfarming because of their robustness and their rapid growth. Three species are
currently well studied for domestication: Clarias gariepinus, Heterobranchus longifilis and Chrysich-
thys nigrodigitatus. For example, Heterobranchus longifilis is present in most of the river basins of
intertropical Africa, and has biological characteristics which are particularly favorable to fishfarming:
capacity to support hypoxic conditions because of air breathing apparatus, omnivorous diet, high
fecundity and quasi-continuous reproduction, remarkable growth potential (10 g per day). The repro-
duction of these species in captivity is controlled, but the larval growing remains the most constrai-
ning phase of the farming. The fishfarming potential of other catfishes, such as Clarias isheriensis,
Bathyclarias loweae, Heterobranchus isopterus or H. bidorsalis, also was the subject of an evalua-
tion. Tests on Auchenoglanis occidentalis were carried out in Ivory Coast.
Some species of Siluriformes are strictly piscivorous and were tested for the control of the po-
pulations of tilapia in the case of polyculture. In addition to Heterobranchus longifilis, Schilbeidae,
like Schilbe mandibularis, S. mystus and S. intermedius and Bagridae, Bagrus docmak, B. bajad…
can be used.

II.3. THE CYPRINIDAE
Despite the abundance and diversity of Cyprinidae in African inland waters, with more than 500
described species, no species has actually been domesticated so far. Yet some species exceed
50 cm TL like Labeobarbus capensis (99 cm TL), and Barbus altianalis (90 cm TL). There was some
attempts to introduce Asian Cyprinidae as common carp (Cyprinus carpio), silver carp (Hypophthal-
michthys molitrix), mottled carp (Hypophthalmichthys nobilis) and grass carp (Ctenopharyngodon
idella). The common carp was first introduced to Madagascar and then scattered in a dozen other
countries including Kenya, Cameroon, Malawi, Ivory Coast and Nigeria. Tests were made with Labeo
victorianus (41 cm TL) and Labeo coubie (42 cm TL). However, these are often species of running
water and this can be a problem on their farm in pond where water is almost stagnant.


II.4. OTHER FAMILIES AND SPECIES
In Annexe a list of species produced commercially in fishfarming in Africa, by country listed by
FAO is presented (Annexe 02 p. 193).
Other species, produced or not, but used also, in tests, like Nile Perch (Lates niloticus, Latidae,
167 cm SL), the predator introduced into Lake Victoria, for production and the control of the popu-
lations of tilapia in pond.
Other species were tested, but the results are old and not easily findable in the bibliography.
The domestication of new African species is considered. It is for example Gymnarchus niloticus (in
Nigeria, Gymnarchidae; 167 cm SL for 18.5 kg), Parachanna obscura (Channidae, 50 cm SL for a
maximum weight of 1 kg), Distichodus niloticus (Citharinidae, 83 cm TL, for a weight of 6.2 kg),
In polyculture, a species used regularly is the Arapaimidae, Heterotis niloticus (100 cm SL, for a
weight of 10.2 kg), in Ghana, in Nigeria, in Gambia, in Guinea and in Congo.

It is clear, however, that the people quickly focused on less than 10 species. However, the po-
tentials of many others were not tested and, within sight of the damage caused by the introductions
of species, it would be advisable to develop the farming of indigenous species.
One of the interests of the step of identification of indigenous species aiming at determining
those having a potential interesting for the fishfarming, is to highlight neglected and badly known
species revealing a potential higher than that of a species sister or a very nearby genus previously
used; the other is that to avoid the introduction of allochtones species. Such is the case for example
of Chrysichthys nigrodigitatus compared to C. maurus or that of Heterobranchus longifilis compared
to Clarias gariepinus. This is also for the aim of diversification

Ö We should think that «what is found elsewhere is not better than what we find at home.»


Summary
FISHFARMING: AIM AND ISSUES
WHY?
Fisheries and aquaculture contribute to the food security primarily in three ways:
Ö To increase the food availabilities,
Ö To provide highly nutritive animal proteins and important trace elements,
Ö To offer employment and incomes which people use to buy of other food products.

PRESSURE ON THE RESOURCES
The continental aquatic ecosystems are particularly affected by the human activities by:
9 Modifications of the habitat,
9 Water pollution,
9 Fsheries impact,
9 Introductions.

INTERNATIONAL ASPECTS
The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention,
is an international treaty that was adopted at the Earth Summit in Rio de Janeiro in June 1992. The
Convention has three main goals:
1. Conservation of biological diversity (or biodiversity);
2. Sustainable use of its components;
3. Fair and equitable sharing of benefits arising from genetic resources.

Ö Above all, the Convention is legally compulsory, the member states are forced to im-
plement its mesures.
Ö This means to respect these mesures in the projects on the field while avoiding up to
have an effect on the environment that may affect biodiversity. If so, this could turn against
the organism responsible for the project despite the intentions and the tacit agreement of
local and regional authorities.

OBJECTIVE OF FISHFARMING
Ö The objective of the fishfarming is not to replace fisheries but to supplement its contri-
butions in maintaining the current level of fish consumption, regarding the increase of
world population. However, this goal must be pursued in respect of environmental, consu-
mer health and bioethics.

TYPE OF FISHFARMING
VARIOUS TYPES OF FISHFARMING
The types of fishfarming depend mainly on the investment, the quantity of fish produced per unit
of area and on the destination of the products. They are generally characterized by their degree of
intensification.


A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE
So a fishfarm in extensive to semi-intensive, of production, requiring minimal technical to be
easily reproducible will be preferable. This, while producing in a rather short time a quantity of fish of
consumable size. It is a fishfarming of self-consumption but artisanal.
Important points:
9 Minimum of technique for a good appropriation by the beneficiaries,
9 Reduced impact on the environmental context: local species,
9 Fast production with lower costs,
9 Minimum of intervention on the ponds by the beneficiaries who have other major activities,
9 Minimum of inputs: alive or material.
9 Potentialities of Incomes Generating Activities (IGA): according to the size of the fishfarming
and the number of ponds, one can arrive at a system allowing a IGA with use of people for the current
maintenance and care on the ponds, while keeping an extensive system of production, because of
technicality requested.

POLYCULTURE VS MONOCULTURE
Monoculture is the principle of using only one species in production in the fishfarm structures.
Polyculture is the association of fish with different diets which increase the net yield and value of
production.

Ö One therefore choose a fishfarming system of production, semi-intensive, of self-
consumption to artisanal, using polyculture rather than monoculture that request external
food input and a more important follow-up if one want an interesting production.

BIOGEOGRAPHY AND FISH SPECIES
GEOGRAPHY
The fish faunas were established and have evolved according to the history of aquatic systems
they occupy. They are far from being homogeneous for the whole of Africa.
The African continent can be separate in several great ichthyologic regions or ichthyoregions.
They were defined according to affinities between fish faunas.

Ö It will be necessary to check in which country the intervention must take place and see
the corresponding ichthyoregion.

THE SPECIES
Aquaculture production is based primarily on two groups of species: the Cichlidae with tilapia
and Siluriformes or catfish.
Individually, the species of tilapia and catfish are not necessarily distributed over the whole of
Africa. But both groups are everywhere.

Ö It will thus be a question of paying attention to the source of fish to be used and the
drainage basin where the action is undertaken, this, because of the risks incurred by the
introduction of fish and the national and international legislative aspects concerning the
biodiversity
Ö It is not either because a species was already introduced into the zone of intervention,
that it should necessarily be used.
Ö We should think that «what is found elsewhere is not better than what we find at home.»


Part II
PRACTICAL ASPECTS

Contents
• The initial pre-project assessment Implementation plan
• Villages selection
• Sites selection
• Characteristics of ponds
• The construction of ponds
• Biological approach
• The handling of the fish
• Maintenance and management of
the ponds


CONTENTS - PART II

Chapter 04 - THE INITIAL PRE-PROJECT ASSESSMENT 33
I. THE ECOSYSTEM 33
II. THE ASSESSMENT 36
III. PRINCIPLE 37
IV. BIOLOGICAL AND ECOLOGICAL ASSESSMENT 38
V. SOCIO-ETHNOLOGY 40
V.1. Socio-economic and cultural characteristics 40
V.2. The relations man-resources 40
V.3. The relations man-man 41

Chapter 05 - VILLAGES AND SITES SELECTIONS 43
I. THE VILLAGES SELECTION 43
II. THE SITES SELECTION 45
II.1. The water 45
II.2. The soil 50
II.3. The topography 53
II.4. The other parameters 56

Chapter 06 - CHARACTERISTICS OF THE PONDS 59
I. DESCRIPTION 59
II. TYPES OF PONDS 59
II.1. Barrage ponds 62
II.2. Diversion ponds 62
II.3. Comparison 62
III. CHARACTERISTICS 63
III.1. General criteria 63
III.2. Pond shape 66
III.3. According the slope 67

Cover photo:
Ö Villagers working on the pond, Liberia, ASUR, 2006 - © Yves Fermon


III.4. Layout of ponds 67
III.5. Size and depth of the ponds 68
III.6. Differences in levels 69
IV. SUMMARY 71

Chapter 07 - THE CONSTRUCTION OF POND 73
I. THE DESIGN PLAN 73
II. THE CLEANING OF THE SITE 75
III. WATER SUPPLY: WATER INTAKE AND CHANNEL 77
IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE 81
V. THE PICKETING OF THE POND 82
VI. THE CONSTRUCTION OF THE DIKES 83
VII. THE DEVELOPMENT OF THE PLATE (BOTTOM) 89
VIII. THE CONSTRUCTION OF THE POND INLET AND OUTLET 90
VIII.1. Pond inlet structures 90
VIII.2. Pond outlet structures 94
VIII.3. Sedimentation tank 105
Ix. ADDITIONAL INSTALLATIONS 106
Ix.1. The anti-erosive protection 106
Ix.2. The anti-erosive fight 107
Ix.3. Biological plastic 108
Ix.4. The fence 108
Ix.5. The filling of the pond and tests 109
x. NECESSARY RESOURCES 109
x.1. Materials 109
x.2. Human Resources and necessary time 110
xI. SUMMARY 112

Chapter 08 - BIOLOGICAL APPROACH 113
I. THE LIFE IN A POND 113
I.1. Primary producers 115
I.2. The invertebrates 116
I.3. The vertebrates 118


II. THE FERTILIZATION 118
II.1. The fertilizers or manure 118
II.2. The compost 121
III. SUMMARY 126

Chapter 09 - THE HANDLING OF THE FISH 127
I. CATCH METHODS 127
I.1. Seine nets 129
I.2. Gill nets 132
I.3. Cast nets 133
I.4. Dip or hand nets 134
I.5. Traps 135
I.6. Handline and hooks 136
II. THE TRANSPORT OF LIVE FISH 136
III. THE PRODUCTION OF FINGERLINGS OF TILAPIA 139
III.1. The recognition of the sex 139
III.2. The nursery ponds 139
III.3. Hapas and cages 142
III.4. The other structures 145
IV. THE STOCKING OF THE PONDS 146
V. THE FOLLOW-UP OF FISH 149
VI. DRAINING AND HARVEST 150
VI.1. Intermediate fishings 150
VI.2. Complete draining 151
VII. SUMMARY 152

Chapter 10 - MAINTENANCE AND MANAGEMENT OF THE PONDS 153
I. THE MAINTENANCE OF THE PONDS 153
I.1. The diseases of fish 153
I.2. The feeding of the fish 158
I.3. Daily activities of follow-up 162
I.4. Maintenance work after draining 163
I.5. Fight against predators 164


I.6. Summary 164
II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION 165
III. THE MANAGEMENT OF PONDS 167
III.1. Fish Stocks and useful indices for monitoring 167
III.2. The expected yields 168
III.3. The management of harvests 168
III.4. Several kinds of production costs 170
III.5. Record keeping and accounting 170
III.6. The formation 171

IV. PONDS AND HEALTH 171

On the next page, the reader may find the overall implementation plan
for the establishment of ponds.
The chapters follow the plan. As the progress of the manual, it will be
mentioned at the beginning of each chapter showing step processed.


0
Assessment
Socio-economy Environnemental
Duration: Ethnology Ecology - Ichthyology
3 months
3 months
Selection
Villages selection Sites selection

Ponds
Laying out plan
Purchases of the
equipment
Cleaning of the site

Staking out the pond

Water supply channel Ponds inlet
Time

Building of the dikes

Draining channel Ponds outlet

Pond bottom drain laying out
Purchases of
fishing nets
Building of cages Other structures laying out
or hapas

Duration: Completion and filling in water
6 - 9 months 3 to 6 months

Fish farming
Collection in natural Fertilization Outside composter
water or production of
juvenils of tilapia
« Green water » Maintenance and Resumption of a cycle
61/4 - 91/4 months follow-up of the
ponds
Collection in natural
Stocking with tilapia
water of predators
Follow-up
of the fishes
7 - 10 months Stocking with
Duration: predators
4 to 12 months

End of the cycle Intermediate harvest
of fishes
11 - 22 months Storage of Draining of the pond
fishes and harvest
Maintenance and
repair of ponds after
Sale andor transformation
Duration: draining
0.5 to 1 month of the fish

Figure 8. General implementation plan.


Chapter 04
THE INITIAL PRE-PROJECT ASSESSMENT
Initially, the phases of evaluation intervene o determine the utility and the relevance for the popu-
lations of the implementation of any project. This would take into account:
9 Requests of populations,
9 Available resources and environment.
As a first step, we will describe the environment and ecosystems. Then we discuss the various
aspects of evaluation. This step has a duration of at least 3 months, which may increase depending
on the importance of the program and the geographical area to assess (Figure 9, p. 34).

I. THE ECOSYSTEM
An ecosystem is a dynamic complex composed of plants, animals and micro-organisms and
inert nature, which is subject to complex interactions as a functional entity. Ecosystems vary greatly
in size, lifetime and operating. A temporary pond in a hole of a tree and an ocean basin are both
examples of ecosystems.
The communities of plants, animals and micro-organisms form a biocoenosis. This one is cha-
racterized by a food chain (or trophic), from the primary producer (the plant build the organic
matter starting from light energy, CO2 of the air and the mineral ions of the ground), to the various
consumers (from the herbivorous to the super predator), while passing through the various decom-
posers in charge of ensuring the return of organic matter in mineral form in the soil. Inert nature is
also known as the biotope. It includes all geographical and physicochemical ecosystem charac-
ters (climate, soil, topography, water…) To analyze and describe a given ecosystem, one uses the
concept of factor ecological. Is known as ecological factor, any element of the external environment
which may affect the development of the living beings. For this reason, one distinguishes several
types of ecological factors:
9 Biotic factors, related to the biological components (biocénose), interactions of alive on
alive, intraspecific (within the same species) and interspecific one (between two different species or
more);
9 Abiotic factors, related to the physicochemical conditions of the environment (biotope).
An ecological factor acts as a limiting factor when it determines the potential success of an or-
ganism in its attempts to colonize an environment. This factor can be limiting as well by its absence
as by its excess. With respect to the ecological factors, each living being thus presents tolerances
limits between which is located the zone of tolerance and the ecological optimum. Thus the ecolo-
gical valence of a species represents its capacity to support the more or less large variations of an
ecological factor.
The ecological factors can thus act in various ways on the biocénose. They in particular will
intervene on:
9 The biogeographic distribution area of the species;
9 The density of the populations;;
9 The occurrence of adaptive modifications (behavior, metabolism).
Thus when the presence of such or such species informs us about the characteristics of its en-
vironment, this one is called biological indicator. The particular characteristics (a biotope implying
such type of biocoenosis and conversely) of each ecosystem allow a zoning. Consequently for each
type of ecosystem, it is possible to associate with this zoning: an operating process, goods and
services produced, known risks and threats…
The human beings, as an integral part of the ecosystems, draw benefit from the “goods and
services” produces by the functioning of the ecosystems. The services provided by the ecosystems
include the services of deduction such as food and water; services of regulation like the regulation


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time


Drainig channel Ponds outlet

Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia

61/4 - 91/4 months
follow-up of the
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining

Figure 9. Setting of fish ponds: 1. Assessment.


1. ASSESSMENT
of the floods, the dryness, the disease and impoverishment of the soil; services of self-maintenance
like the formation of the grounds, the development of the nutritional cycle; finally culture sections
like the benefit of approval, the esthetic benefit and the other nonmaterial advantages. These various
“services” result from the functioning of the ecosystems, i.e. of the whole of the biogeochemical
reactions affecting the biosphere and being characterized by permanent exchanges of matter and
energy along the various cycles (water, carbon, nitrogenize…) and food chains.
Because of the various cycles (like that of water, Figure 10 below), all the ecosystems are strongly
open the ones to the others. There exist however more or less porous borders called ecotones. The
edge of a wood separating it from an agricultural field, a hedge cuts wind are good examples. Like
any border, these zones are important places of transit and exchange. One of the most known eco-
tones is the wetland, zone of transition between the terrestrial and water environments. The wetlands
constitute a vast inter-connected network of exchange including the lakes, rivers, swamps and the
coastal regions.
The living conditions and production of a human community depend always directly or indirectly
on the abundant services by the local ecosystems (water, food, wood, fiber, genetic material…). As
example, the exploratory studies undertaken within the framework of “Millenium Ecosystem Assess-
ment” teach us that the demand for food (thus in service of deduction, of self-maintenance…) could
grow from 70 to 80 % over the 50 next years. With which ecosystems? This increasing demand will
generate necessarily larger difficulties for the communities on the level of the access to the resources
and will increase for all, the cost of the security of the provisioning, from where the concept of terri-
torial vulnerability.
Because of interconnection of all the ecosystems, heterogeneous scales of time cross on the
same territory: global environment (climate, biogeochemical major cycle) which evolves over a long
period, local environment (production of biomass) over the medium period, human communities over
the short period. What to say on climate change, true producing of uncertainties affecting the global
environment. These moving temporalities and borders within the territories reinforce the prospective
need for the analyzes.

Evapotranspiration
Precipitation

Evaporation

Surface runoff

Stream flow

Source
Infiltration
Sea
Ground water flow

Figure 10. Water cycle.


To take account of these dependences and inter-connected multiple, of variable contamination
temporalities and distances, the ecosystemic approach of the territories appears most relevant.
Thus let us retain that there exist direct and indirect relationships between vulnerability of the
environment, within the meaning of the whole of the ecosystems present on a territory, and vulnera-
bility of the human communities which there are included and fully live, in a territory, on goods and
services gotten by its ecosystems.

Ö It will thus be a question of carrying out the evaluation of the ecosystem in all its com-
ponents, human beings included, in order to see which are the actions to propose to en-
sure a better “wellbeing”, mainly of food safety but also of health and water and sanitation.

II. THE ASSESSMENT
It will thus be a question of evaluating:
The 3 points according the Figure 11 below: According the 2 major issues:
1. The men. (i) Biology and ecology: points 2 and 3.
2. The ressources.
3. The human actions on the ressources. (ii) Socio-ethnology: points 1 and 3

The ideal would be to be able to carry out these two topics of evaluation jointly.
In the case of the interventions in post-urgency, one of the factors limiting is time. It will thus
be necessary to center mainly the intervention in the shortest possible time and to carry out a “fast
evaluation”.

FIELD - ECOSYSTEM

2

3 1

RESOURCES VILLAGE

Figure 11. Contextual components of the assessment.
1: The men; 2: The ressources; 3: The human actions on the ressources.


1. ASSESSMENT
III. PRINCIPLE
The fast evaluation can be defined like:
“A synoptic evaluation often undertaken in urgency, within the shortest possible time possible, in
order to produce results reliable and applicable to the definite goal”.
Whatever the fast evaluation that one prepares, it is necessary to take into account of the nine
following points:
1. The fast type of evaluation. The fast evaluation can go from a theoretical study to a field study,
through meetings of groups of expert and workshops. It can include/understand compilation of
existing knowledge and specialized data, including traditional knowledge and data, and methods of
study in the field.
2. The evaluations can be done in three stages: design/preparation, application and esta-
blishment of the reports. The fast evaluations provide the necessary results within the practical
shortest times, even if the preparatory period and the work of planning which precede the study
are consumers of time. In some circumstances (when one takes account of seasonal factors, for
example) it can run out of time between the decision to undertake the evaluation and its realization.
In other cases (in the event of disturbance and of catastrophe, for example), the evaluation will be
undertaken in urgency and the preparation time must remain minimal.
3. Inventory, evaluation and follow-up. When one conceives exercises of data acquisition the
type of necessary information is different in each case and it is important to distinguish the inventory,
the evaluation and the follow-up. The inventory of reference of the wetlands is used as a basis for
the development of a suitable evaluation and a follow-up. The inventories of the wetlands, repeated
with certain intervals, do not constitute necessarily a “follow-up”.
4. The cost increases, in particular, during the evaluation of isolated zones, in the case of vast
space scales, of a topographic high-resolution and/or a great number of the types of characteristics.
The cost of an evaluation undertaken quickly will be higher, for example, because it is necessary to
have large teams in the field simultaneously and to support them.
5. Space scale. The fast evaluations can be undertaken on various space scales. In general, a
fast evaluation with large scales consists in applying a standardized method to a great number of
localities or stations of sampling. It is clear that the more the zone is extended, the more time reques-
ted can be long, depend on the number of implied people, and thus the higher cost.
6. Compilation of the existing data/access to the data. Before deciding to carry out a new
evaluation on the field, the first big step consists to compile and evaluate the highest possible num-
ber of data and information existing and available. This part of the evaluation should determine the
data and the information which exist like their accessibility. The data sources can include the geo-
graphical information systems (GIS) and the teledetection, the data published and not published
and traditional knowledge and data obtained by the contribution of local populations and indige-
nous. This compilation must be used as lack analysis making it possible to determine if the goal
of the evaluation can be reached with existing information or if it is necessary to lead a new study
in th field. A good cartography is essential to the good way of the evaluation and the future
decisions concerning the projects to be proposed.
7. For all new data and information collected during a later fast evaluation in the field, it is essen-
tial to create a traceability of the data.
8. Reliability of the data of fast evaluation. In all the cases of fast evaluation, it is particularly
important that all the results and products contain information on the confidence limits of the conclu-
sions. If possible, it is advisable to evaluate the propagation of error by the data and information
analysis to provide a comprehensive assessment of the confidence limits of the final results of the
evaluation.
9. Diffusion of the results. An important element of any fast evaluation is the fast, clear and
open diffusion of the results near a range of actors, decision makers and local communities. It is
essential to present this information to each group in the form and with the level of precision which
is the best appropriate.


In this case, two aspects are to be treated and, preferably, jointly, in relation to the wetlands and
its resources:
Ö The biological aspect and resources;
Ö The socio-ethnological aspect and the man.

Ö Preferably, two specialists will be necessary with priority for the biological aspects.

IV. BIOLOGICAL AND ECOLOGICAL ASSESSMENT
The methods available for a fast evaluation of the biodiversity of the wetlands are dependant on
the goal and the results of specific projects. The factor of the available resources and the limitations
is quite as important, in particular because it influences the range of the evaluation. Time, the money
and the expertise are limitations of resources which determine the methods available for a particular
project of evaluation. Moreover, they define the project from the point of view of its range in the fol-
lowing fields: systematics, geography, choice of the site, analyzes, data and sampling procedures.
They are important components of an evaluation of the biodiversity of a wetland and the range or the
capacity of each one varies according to the needs for the project and its limits in resources.
One of the points important is to establish the statement of the area.

Ö The hydrographic network of a country is its “blood system”. Any damage in a point will
be found downstream from this point, wether it is chemical, urban, related to erosion…
Water, it is the life. Current and well-known sentence but in the health, water and sanitary
and food security (agriculture, fish), it is the main common factor. As for the human body
where one looks at the blood system to establish a diagnosis, one can study the rivers
to evaluate the health of an area and to thus know the points where it is necessary to
intervene.

One of the best indicators to evaluate water quality is its biological components e.g invertebrate
(crustaceans, molluscs, insects…), vertebrate (fish). An evaluation of the indicators supposes that
biological diversity, from the point of view of the diversity of the species and the communities, can
give informations on water quality, the hydrology and the health in general of particular ecosystems.
The “biomonitoring” is a monitoring often associated with this type of evaluation. Traditionally, that
relates to the use of biological indicators to follow-up of the levels of toxicity and the chemical
contents, but recently, this type of approach was more largely applied to the follow-up of the total
health of a system rather than of its physical and chemical parameters only. The presence or the ab-
sence of some chemical or biological indicators can reflect the environmental conditions. The taxo-
nomic groups, the individual species, the groups of species or the whole communities can be used
as indicators. Usually, the benthic macro-invertebrates, the fish and the algae are used as organic
indicators. It is thus possible to use the presence or the absence of species, and in certain cases the
abundance and the characteristics of the habitat, to evaluate the state of ecosystems of wetlands.
The use of biological criteria to follow the quality of the courses of the rivers in temperate countries is
common. It is less the case for the tropical countries. The biological index of integrity (IBI) has been
used for more than 10 years in Europe and North America. It allows an estimate of the health of a
river by the analysis of its fish settlement. The maintenance of water quality is a major concern for
human society which must provide for increasingly important requirements of water, and this, as well
from the quantitative point of view as qualitative.
The evaluation of the resources has the aim of determining the durable potential of use of the
living resources in a given zone or a given aquaic system. The data deal with the presence, the state


1. ASSESSMENT
and the conditions of economic species, of species on which depend the means of existence and
of species which have a potential commercial value. In good logic, it would be good that an eva-
luation of the resources facilitates the ecologically durable development rather than or not durable
destroying activities. The importance of the choice of fish as indicator is its importance also as an
animal protein contribution. It is a question of surveying which are the resources available in the
rivers close to the targeted villages.
It is supposed that any fast evaluation must be done with the end objectives of conservation
and rational use. The methods used are supposed to increase knowledge and understanding for the
purpose of establishing a reference, the evaluation of the changes in the ecosystems or their state
and the support to the durable use of the resource. In this context, there are five precise reasons to
undertake a fast evaluation of the wetlands which cover the extent of the possible reasons:
1. To collect general data on the biodiversity in order to inventory and to treat on a hierarchical
basis the species, the communities and the ecosystems of the wetlands. To obtain reference infor-
mation on the biodiversity for a given zone.
2. To gather information on the status of a target species (such as a threatened species). To
gather relative data with the conservation of particular species.
3. To obtain information on the effects of the natural or induced disturbances (changes) by the
man on a zone or a particular species.
4. To obtain indicating information of the general health of an ecosystem or of the statement of a
particular ecosystem of wetland.
5. To determine the possibility of using in a durable way the living resources in an ecosystem of
a particular wetland.
Many fast evaluations do not allow to entirely evaluate the threats or the pressures on biological
diversity. Nevertheless, it can be useful, in order to determine it on what should carry a future evalua-
tion, to make a provisional evaluation of the categories of threats.
It is important to note that the methods of fast evaluation of the wetlands are generally not made
to take into account the variations in time, like the seasonal character, in the ecosystems. However,
some methods of fast evaluation can be (and are) used in iterative studies as elements of a program
of integrated follow-up, in order to take account of this variation in time. The techniques of fast eva-
luation are appropriate particularly at the specific level of biological diversity and the present orienta-
tions are interested in the evaluations on this level. The evaluations on the genetic level of biological
diversity generally are not related to “fast” approaches.
Nature complexes and the variability of the ecosystems of the wetlands make that there does
not exist universal evaluation fast method, applicable to all the range of the types of wetlands and to
the diversity of the goals for which the evaluations are undertaken. Moreover, which it is possible to
make, in a particular case, depends on the resources and the capacities available.
In a general way, the goal is to gather as much information than possible on an ecosystem of
wetland by sampling wide and as complete as possible of the biological elements and associated
characteristics. The lists of species and habitats will be probably the most important form of data, but
of other relevant data could include: species richness, abundance, relative size of the populations,
distribution and the surface of distribution, cultural importance in addition to the importance for the
biodiversity and other relevant biological information which is due to water quality, the hydrology and
the health of the ecosystem. The data on the geography, geology, the climate and the habitat are
also important. For the majority of the studies, it would be good to measure a diversity of variables
of water quality. Those can include the temperature, electric conductivity (EC, a measurement of
dissolved total salts), the pH (measurement of the acidity or alkalinity of water), chlorophyl A, total
phosphorus, total nitrogen, oxygen dissolves and the transparency of water (with the disc of Secchi).
These variables can be measured with individual instruments or a combination of instruments inclu-
ding several types of probes. One can seek the macrophytes visually. The fish can be sampled with a
great diversity of methods, while taking into account the applicable legislation. To work with the local
fishermen and to examine their catches can be also an invaluable source of information.
In order to ensure this part properly it is essential that a specialist can intervene. A generalist
will be limited by his knowledge concerning the aquatic organisms and the functioning of the eco-
systems.


The data essential and minimal to collect are:
Ö The number of species,
Ö Quantity of individuals by species for a given time of sampling,
Ö The presence/absence of pilot species,
Ö The physicochemical quality of water (rate of nitrates/phosphates, pH, Oxygen, conductivity,
turbidity).
In the collected species, one will be able to thus see which are available for fishfarming.
The local communities can be an important source of information on the richness of the species
in a given habitat. One can, for example, by studies of the communities and consumption, to gather
information in very short time. From where, the importance of a joint analysis with an socio-ethno-
logical approach.

V. SOCIO-ETHNOLOGY
V.1. SOCIO-ECONOMIC AND CULTURAL CHARACTERISTICS
It is also important to gather information on the socio-economic and cultural characteristics
of biological diversity although a complete economic evaluation is, generally, out of reach in fast
evaluation. Nevertheless, within the framework of a fast evaluation of inventory or an evaluation of
the risks, it can be useful to obtain a first indication of the socio-economic and cultural characteris-
tics which have an importance for the study of the site. That provides an indication of the probable
changes in the base of natural resources and can be used to determine the characteristics which
should be the subject of a more detailed evaluation of follow-up.
It is advisable to take into account in particular:
1. Paleontological and archaeological registers;
2. Historical buildings and artefacts;
3. Cultural landscapes;
4. Traditional systems of production and agro-ecosystems, for example exploited rice planta-
tions, saltworks, estuaries;
5. Practices of collective management of water and lands;
6. Practices of self-management, including the usual property rights;
7. Traditional techniques of exploitation of the resources of the wetlands;
8. Oral tradition;
9. Traditional knowledge;
10. Religious aspects, beliefs and mythology;
11. “Arts” - music, song, dance, painting, literature and cinema.
In addition to the traditional evaluation of the nutritional and medical state of the local population,
It is advisable to raise several questions when one arrives in an inhabited area.

V.2. THE RELATIONS MAN-RESOURCES
¾ Do there exist taboos? beliefs? It will be a question of evaluating the relations man/fish/river
(belief).
Food taboos exist, to differing degree, in all the cultures. It is obvious that food, basic element
with the subsistence of the man (like other living beings), is a field where distinction between allowed
and forbidden, the pure one and the impure one, is fundamental, for medical reasons, morals or
symbolic systems. The taboos can have several justifications: nuns, medical, morals, psychological
and emotional. These various justifications may be mixed. There other habits relate to fish and assign
still the women and the children. It may be that it is about a true taboo, although often people who
are not accustomed to eat fish do not like it for the simple reason that “smell bad” or “resembles
a snake”. In some communities, the range of the taboos for the pregnant mothers was formerly so


1. ASSESSMENT
wide that it was almost impossible for them to have a balance diet. For example, part of the Bahaya
people which live close to Lake Victoria was accustomed to prohibiting the egg and milk, fish, meat
consumption to the pregnant women. Do there exist fish known as “patrimonial” i.e. having an im-
portance to the level of the symbolic system?
In other cases, there is the prohibited fishing in some areas throughout a village. Some of these
prohibitions were put in place just to avoid an excessive level of predation in an area rich in fish and
thus the management of fish resources.
¾ How is fishing perceived?
In a certain number of ethnos groups, the practice of fishing is regarded as an activity for the
lower castes. To be fishing and live fishing then are very discredited.
¾ Which are the resources used?
By looking at the women preparing the meals and what they prepare, while carrying out of the
visits at the market, one will be able to realize on behalf of fish in the food day laborer. In Ethiopia,
for example, the fish is consumed mainly at the time of the Lent. If the fish is present in the food, it
will then be a question of making sure of its source and its availability. For example, in Liberia, the
villages near the rivers did not have any problem of supply fish in spite of an interest for fishfarm,
whereas 10 km further, another village had supply problems.
¾ Which are the produced resources?
A visit of the fields and a census of the cattle and animals present make it possible to realize of
the diversity of the food products available. It will be necessary, however, to separate well the cattle
which would be of “prestige” with the animals used for the human consumption.
¾ What are the water supplies?
An important aspect is the supply of water for people. It will therefore seek the water points
where people will be provided (well, pump, river…) and assess their condition.

V.3. THE RELATIONS MAN-MAN
¾ Who does what? Which is the role of the women and of the men? Uses and tasks.
There is a division of labor between the men and the women. Among fishing people, most of the
time, they are the men who go to fishing but the women deal with collecting fish, to transform it and
sell it. At others, fishing is practiced by the women and becomes a corporate measure. In Liberia, the
women with the children go away the afternoon to the river to capture with large scoops nets. They
take the opportunity to exchange the latest news from the village.
¾ Which is the social structure?
The way in which the village is structured is particularly important to know on which scale and
which are the key and notable people. The groupings, their operation…, are a key of the success of
programs in the field.
¾ Which is the system of division of the lands?
The type of division of the lands, their membership, the land rights are as many variables which
are important to know insofar as fishfarms will be established on some privileged zones. Water and
its management are also an important parameter.
Most of the time, this information can be collected in the form of investigations for which huma-
nitarian NGOs like ACF have good experience in the past. It is, however, important not to be satisfied
to discuss with the villagers, as that is sometimes the case.

In some cases, one will have to deal with communities which have already experience of fish-
farming, often with failures. The system especially developed in countries having an old fishfarming
tradition and where ancestral know-how, although empirical, plays a crucial role. The many attempts
at transfer of these fishfarming models towards countries where there was no fishfarming tradition
failed.


Many explanations were put forward to analyze the difficulties encountered in the development
of fishfarming in Africa:
Ö Of social order, rural populations not having traditions and thus knowledge in this field;
Ö Of technical order, on recent time, the techniques of fishfarming were not controlled yet
perfectly, which had as a consequence a poor production in quality and quantity;
Ö Of economic order, the fishfarming developed in the context of an activity of subsistence
in family matter, generally without profitability.
We must therefore ascertain the presence of former ponds for fish production. If so, the chal-
lenge will be to unlearn first to allow relearning.

Ö The whole of collected information will allow:
Ö To know the statement of the zone where the intervention must take place;
Ö To know the available resources usable and their current use;
Ö To know the communities and social structures.
Ö The goal being to have the elements to propose a solution allowing a good appropria-
tion of the project by the populations, if the various components make it possible to affirm
that fishfarming is a solution for the zone considered.


Chapter 05
VILLAGES AND SITES SELECTIONS
If the initial assessmenst justify an intervention, the first stage will be thus to choose villages of
establishment, by making sure that those have adequate sites in the vicinity (Figure 12, p. 44). This
choice can be already more or less defined according to the preliminary assessment and of the visits
of field which took place during this evaluation.

I. THE VILLAGES SELECTION
As in all the actions undertaken under development and post-urgency, the choice of the villages
and communities, then that of the beneficiaries is particularly delicate. In the majority of the cases,
the target goes on the populations considered as most vulnerable.

Various points will decide the approach of villages:
9 The first aspect inherent in the way of operating of ONG will be the presence of populations
said vulnerable.
9 Proposed projects are usually fairly short. The number of villages targeted should therefore
be chosen depending on the duration and logistics that will be available. However, it is unrealistic
to propose a fishfarming project for less than 12 months. Indeed, the establishment of a pond of
200 m2 overall request 20 days to 20 people. If it is the beneficiaries who lead the workforce, it must
take into account the fact that for most, their main activity is agriculture and they thus will devote only
a time restricted to the construction of the pond.
9 One will not be able to also choose villages too distant because of times from transport
and inherent logistics. Often, the technicians are used as catalysts for the beneficiaries and their
presence is essential for the motivation and the follow-up. In the same way, the roads are often da-
maged and not very practicable. For that, a good cartography is essential and can be implemented
during the evaluation.
9 No sources of fish in quantity near. Indeed, the presence of close sources of fish in conside-
rable quantity will be a brake for the development of fish ponds. Unfortunately, many times, there will
be the certainty which the villagers are motivated whereas in fact, their interest is located especially
to obtain something on behalf of international NGOs operating in the zone. It will often be a total
fiasco as the village investment in building ponds. It will thus be a question of seeing well whether the
proteins fish are essential and missing in the zone. This means to see if the fish proteins are essential
and missing in the area. This will be particularly important if the request comes from the villagers, this
will bring more weight to their request.
9 Presence of sources or rivers near the village
It is one of the crucial points of the choice of the villages and which will be taken again more
in detail in the following paragraph (paragraphe II, p. 45). It is essential that the village has enough
running water nearby.
9 The motivation of the villagers.
It is one of the delicate aspects. It is very difficult to judge at first the general motivation. Gene-
rally, this vision of the motivation will come with the beginning of the work. However, the ethnogra-
phic preliminary study will provide information on the first aspects of this motivation but also of the
elements allowing a good appropriation of the project by the beneficiaries. It is necessary that the
beneficiaries understand that constructions carried out will belong to them and that this work
will not belong at all to the NGO which supports the project, as it will not be used to establish
this type of project if the villagers don’t want it. It is not, certainly, question of imposing any-
thing… If possible, he is advisable to choose family groups people, which will avoids interfamilies
problems for the management and distribution of harvests. If perennial associations would exist, it


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining

Figure 12. Setting of fish pond: 2. Selections.


2. SELECTIONS
will be also possible to work with them according to their motivation and of their social cohesion.
Once this choice will be carried out, it will be a question of passing to the second phase, i.e. the
presence of favorable sites in the selected village.

Ö The choice of the village must take into account:
Ö Vulnerability of the population,
Ö Logistics,
Ö Water resources,
Ö Motivation of the villagers.

II. THE SITES SELECTION
Ö This is the most important step for a fish pond.

The design and the realization of the ponds must allow the most perfect possible control of wa-
ter. Moreover, the quality of the fishfarming works determines also the facility with which the follow-
up, harvest and the sorting can be done. In other words, they determine the feasibility of a fishfarm.
It is advisable to evaluate each potential site by a series of fast feasibility studies to check that the
principal requirements are respected.
In this chapter and the following, the major part of the drawings and texts are classic and often
comes from various booklets, mainly those of FAO.

II.1. THE WATER
II.1.1. AVAILABILITY OF WATER
It will be necessary to take into account of the temporal variations of the inland waters, in par-
ticular the variations in the modes of flow of various types of inland water ecosystems which can
include:
9 Perennial systems which know flows of surface all the year and are not drained during the
drynesses.
9 Seasonal systems which know expected flows during the annual rainy season, but which
can be dry during several months of the year.
9 Episodical systems (periodic or intermittent) which knows flows during one prolonged pe-
riod, but which are neither predictable, nor seasonal. These systems are generally supply as well by
rainwater as by subterranean water. Sometimes, flows of surface can only occur in some parts and
become underground in the others.
9 Transitory systems (with short life) which know briefly and seldom flows and which, between
two, return under dry conditions. Their flow generally comes from precipitations.
A running water present continuously throughout the year (dry and rainy season) facilitates the
management of ponds. One thus will seek the perennial systems.
This allows for a possible renewal of the water of the pond, however slight, and thus have
a good oxygenation and mitigating water loss.
The amount of water needed will depend on the size of ponds, soil and climate prevailing in the
locality.
■ WATER FOR THE BASINS
It is easy to calculate the quantity of water of a basin. It is a simple calculation of volume:
volume = lenght x width x depth
as shown in the Figure 13, p. 46.


Depth measurement

Lenght

Width

Figure 13. Volume of a pond.

■ WATER LOSSES
In addition to a leak in the drain, water losses can occur through infiltration into the substrate
and evaporation.
¾ Evaporation
This component depends on the wind, the humidity of the air and the sunning, i.e. the climate
of the area. Evaporation will be less strong under a cloudy sky than sunny (Figure 14 below). In
equatorial zone, the water loss due to evaporation per day is about 2 to 5 mm height, which can be
compensated by an addition from 15 to 35 liters of water per minute and ha of pond. In intertropical
zone (25°N - 25°S), evaporation almost always exceeds 100 cm per year.
¾ Infiltration
The water losses occur through infiltration from the bottom of the pond and the dikes. If the dikes
are well built, the principal loss will be done by the bottom. It will be also limited by the soil type. In
general, the losses are more important during the first filling of a pond (Figure 15 below).
■ FLOW OF THE STREAM
To have the maximum of profit from a pônd, it is necessary that the pond can be in production
during all the year. There is a need for water throughout the year. It takes water to fill ponds and to
maintain the water level. Water lost through evaporation and infiltration have to be compensated. It

Clouds Sun High temperature
High
evaporation Wind

Low
evaporation
Low
temperature

Figure 14. Water loss through evaporation by weather.

Figure 15. Water loss by ground.


2. SELECTIONS

1 2
Figure 16. Flow measurement for small rivers.

is during the dry season when there is little water, that the losses are large. To maintain water in a
fishfarm of one hectare, it takes 2 to 5 liters water per second. This water flow is thus to control
during the dry season.
On the other hand, we must also check if there is no risk of flooding. People living locally are
better informed. They know if there are significant flooding and water flows all year. You can also
check the marks of water levels on the banks and bridges. A pond should not be built where there
are risks of flood, for example too low to the bottom of the slope. Not only you can lose all the fish,
but the dikes can be destroyed. We also look at whether the banks are planted, so with a water flow
lower than if everything has been cleared along the riverbanks.
The flow of a watercourse is measured in several ways.
For low flows, one will just need a stop watch and a bucket (Figure 16 above). One channels
all the water of the course to fill a bucket with known capacity and one measures the rate of filling.
For more important flows, in the case of absence of adequate measuring devices, one will pro-
ceed as follows:
(i) Determine the wet cross section S in m2 (Figure 17 below) with:

S=lxp

Where l is the width and p the depth.

(ii) Use a stop watch and a half floating object to estimate the speed V in m.s-1 of the flood in
regular zone AB of the stream (Figure 18 below):

V = AB / t

Where t is the time taken for the floating object to travel AB.

(iii) Le flow D in m3.s-1 of the stream is defined by:

D=VxS

l S

A B

p

Figure 17. Measurement of section Figure 18. Measurement of speed V
of the river. of the river.


II.1.2. WATER QUALITY
One can have more water in quantity than necessary, but if its physicochemical characteristics
are not suitable with the fishfarming, fishfarm could not be established. An analysis of water is thus
a prerequisite condition of the choice of the site. More simply, the observation of fish in a river in a
natural state, during a rather long time, can constitute an indicator of good quality of water for fish-
farming (Figure 19 below).
Water is characterized both by the physical parameters (temperature, density, viscosity, co-
lor, turbidity, transparency), and by chemical parameters (pH, conductivity, alkalinity, hardness, dis-
solved oxygen, phosphorus, nitrogen ammonia, nitrites, nitrates, carbon dioxide…).
In a general, the chemical analysis of water must be done preferably in dry season. The strong
evaporation of water in this season allows the concentration of the various components present,
which makes it possible to detect certain extremes.
Quickly, some observations can be made without instruments. Water should not have a bad
smell, neither bad taste, nor an unpleasant color; it should not be too muddy. Avoid the use of very
turbid waters or heavily loaded with suspended particles (muddy water). Often, the water turbidity is
caused by a too fast speed watercourse on a highly erodible land. However, one will be able to use
water charged by implementing a settling tank upstream of the pond.
It will be necessary moreover to take into account of the proximity of factories, because some
industrial wastes can contaminate a water beforehand good quality and make it unusable for fish-
farming. It is thus effluents:
9 Metallurgy factories, which reject lead,
9 Factories of electrolysis (manufacture of batteries for example) which rejects mercury,
9 Refineries which contain phénolés compounds,
9 Agro-alimentary factories as the breweries which can reject fertilizing substances, and
which, to the extreme, can make water eutrophic and not very favourable with fishfarming.
These effluents can kill fish or accumulate in their flesh, which presents a possible hazard for
the consumers.

Ploughing can increase erosion
and cause silt to enter stream Crops

Exhaust gases may
affect local rainwater

Avoid wind drift of
Factories
A curtain of trees can New crops or new methods of planting
spayed pesticides prevent these pesticides or harvesting may affect the quality of
from reaching ponds runoff water from these field

Discharged waste materials may
contaminate water supplies

Pesticides Roads or bridges may increase the
amount of silt or gravel in the stream
Use interception ditches
to avoid pesticide runoff Construction

Quarrying Curting concrete
Gravel from quarry work near a stream may
may block or alter the affect water quality
course of the stream

Figure 19. Examples of factors that may affect water quality.


2. SELECTIONS
A

A B C
Disc 25 cm in
diameter

Weight

Strong string Z
10 cm

10 cm

10 cm
Finished disc and line

Knot 10 cm

Disc

Weight
Knot

Figure 20. Secchi disk. On left: Composition. On right: Transparency measurement:
A = point at which the disk disappears at the decent; B = point at which the disk disappears at the lift;
C = mid-point between A and B, and Z = distance.
The usually measured parameters are the following:
Ö For the physical characteristics: color, transparency and temperature;
Ö For the chemical characteristics: pH, rate of dissolved oxygen, total and carbonated hardness,
and very often, total phosphorus, nitrates and nitrites.
Several types of devices are used for the measurement of these parameters.
The transparency reflects the richness of water in natural foods or suspended particles. It is mea-
sured using the Secchi disc (Figure 20 above). If one does not have this material, it can be arranged
by using a pole, a piece of paper of white polyethylene and a meter. The piece of white paper is fixed
at the lower end of the pole that is vertically immersed in water. One measures the depth where the
white paper disappears from the sight. One continues to immerse it. Then, one goes up and one
again notes the depth to which one sees reappearing paper. The depth is evaluated by the average
of the two readings.
Total hardness translates the quantity of water soluble salts, particularly the ions calcium (Ca2+)
and magnesium (Mg2+) important for the growth of the phytoplankton. A water is hard if its salt
concentration is high, or soft. A water is regarded as good for fishfarming if it has a hardness ran-
ging between 100 and 300 of calcium carbonate Mg (CaCO3). The water hardness translates in fact
its capacity to be able to make precipitate some ions of alkaline salts, of which the ion sodium (Na+)
of the soda (NaOH), used in the manufacture of the soap. Thus, if one does not have materials of
performing the test, one washes the hands with soap by using a sample of water to be tested. It will
be described as soft if it foams immediately and abundantly; it is hard if foam is difficult to come,
possible foam disappearing little time after its appearance. Moreover, the dissolved salt traces re-
main visible on the edges of a stream of hard waters at the low water level when the usual level of
water dropped much.
The pH represents the concentration of water into hydrogen ions (H+), or more simply gives a
measurement of acidity or alkalinity of water. Thus, water is neutral with pH = 7, acid if the pH is


lower than 7 and basic if it is higher than 7. The majority of fish grow rather well in the range of pH
from 6.5 to 9.0.
All these parameters affect directly the development of natural foods. A water is for fish what the
soil is for the plant. If it is of good quality or improvable, it is favourable for fihforming.

II.2. THE SOIL
The soil is a composition of living organisms, organic matters and minerals, water and air. Accor-
ding to their texture, structure and consistency, there exist various types of soils with more or less
air and water.
The physics soil characteristics determine its impermeability just as its capacity to ensure the
stability of the dikes of the ponds, and its chemical characteristics influence the richness of wa-
ter. They include texture (grain-size distribution), the structure (arrangement of the particles of the
nondisturbed soil), the specific weight (concentration of the particles), porosity (proportion of the
vacuums or interparticle spaces of the soil), the permeability (relative resistance of the soil to the
passage of a water flow), compressibility (capacity to become deformed while decreasing by volume
under the effect of the pressure), the shear strength (relative opposition of the soil to the shift), the
color… The clay soils are often the best, taking into account their capacity to retain water and their
high shear strength. A good soil for the construction of brick is in theory good for the construction of
the ponds. The zone of the soil argilo-sandy, limono-silto-argillaceous, limono-argillaceous, limono-
sablo-argillaceous and argilo-silty is most desirable. The very sandy soils do not retain water, while
the purely argillaceous soils are difficult to embank, and especially form not very stable dikes. A soil
which contains too much sand or gravel will not retain water (Figure 21 below).
The color of the soil gives an indication on the drainage of the soil and its composition. However,
the marblings can appear for other reasons (Table VI below). If the marblings are brilliant colors, it is
not a problem of drainage. If the marblings are mattes, usually gray, it is a sign of problem of drainage
for a good part of the year. An abundant yellow clearly characterizes a sulphatic soil with an acid pH.
Texture indicates the relative contents of different particles of size as sand, mud or clay. It allows
to estimate the facility of work to be carried out, the permeability…
For the construction of the ponds, the interesting soils are the argilo-sandy soils because they
retain water easily. Pure clay, the laterite, the black humus and the peat are not good soils for the
construction of the dikes. The black humus, the sandy peat and grounds are too porous except if
one places a clay core to avoid the escapes. Pure clay, once dries, can be cracked. The laterite iosls
are too hard.
There exist simple tests to know quickly the soil texture.

Table VI. Color of the soil and drainage conditions of the soil.
Soil colour/mottling Drainage conditions
Warm colours, browns, reds and oranges Good drainage
Pale yellowish, pale and dark greys with rusty orange Drainage seasonally poor. Water-table at 25- to
and/or grey mottling 120-cm depth
Pale, dark and bluish greys, or pale brownish yellows
Seasonally swampy soil. Water-table at less than
with rusty orange, brown or grey mottling within the
25-cm depth
topsoil

Clay soil Sandy soil

Figure 21. Impermeability of clay and sandy soils.


2. SELECTIONS

If the ball is falling apart,
the soil contains too much
sand

A - Make a ball
If the ball remains com-
pact, the soil contains
enough clay
B - Throw the ball and
catch up with C
Figure 22. Test of the ball (I).

Coarse texture

Moderately coarse texture

Medium texture

Moderately fine texture

Fine texture

3 m
Figure 23. Test of the ball (II).


A - Dig a hole B - Fill it with water to the C - Later, some of the water will
top in the morning have sunk into the soil

D - Then fill the hole with E - Cover the hole F - Result of the test the next morning
water again to the top
Figure 24. Test of soil permeability.

A first test consists in taking a handful of soil on the surface and to compress it in the hand into
a ball (Figure 22, p. 51). (A). Throw the ball in the air and catch it (B). The ball will disintegrate if the soil
contains too much sand or gravel (C). If, on the contrary, it remains compact (D), the soil can be good
for a pond, but, to be sure about it, one will have to carry out another test.
Another test, close to the first, can be carried out (Figure 23, p. 51). Take a quantity of the soil in
the hand, knead it, make mortar and produce a ball of it. Throw the ball on a vertical wall located at
approximately 3 m of the operator. If the ball adheres to the wall, the soil is regarded as good for the
dikes of ponds. It is even more appropriate that the degree of flattening of the adhered ball is low. If
the ball does not adhere, but dislocates itself and fall, the soil will be judged of bad quality and thus
non advisable for the construction of ponds.
A more conclusive test can be carried out. One morning, it is a question of digging a rather deep
hole where one will be able to hold until the waist (A). Then, one fills it of water to the top (B). The
evening, a certain quantity of water will be infiltrated in the ground (C). One again fills the hole to the
top (D). One recovers the hole with boards or branches (E). Lastly, the next morning, if most of water
is still in the hole, it is that the soil retains sufficiently water to dig a pond (F) there (Figure 24 above).
Whatever the other conditions, it is essential that the nature of the soil makes it possible to have
a permanent water reserve. It must thus be sufficiently charged out of clays to obtain all the more
large impermeability as the contributions of water will be irregular or weak. The objective is to have
to compensate for only evaporation. The fact of having at its disposal a favourable topography and a
sandy surface soil is however not harmful as long as a source of clay is available in the vicinity or in
the basement close to surface. Indeed, even of very big hydroelectric dam see their dams built on the
principle of the “clay Mask” recovering of the ground “All coming”. A sandy or humus-bearing soil is


2. SELECTIONS
thus returned seals by contribution of a surface layer of 30 cm thickness clay. A rock ground is often
difficult to work without mechanics, and is sometimes traversed by cracks which it is necessary to
seal by clay.
The chemical characteristics of the soil depends on the colloid concentration, the degree of
saturation in exchangeable bases, the capacity of exchange cation or anion, the capacity to make
available various biogenic salts… The soil must thus contain an amount of exchangeable minerals
salts. This is possible if the soil contains a certain proportion of organic matters. The natural wealth
of water is generally related to the richness of the soil which carries it. The acid soil are to be avoided,
because this acidity can be transmitted to water and harm the growth of fish. It will be necessary in
this last case to invest very heavily in quicklime in order to raise the pH of the water for its fishfarm
use.
The chemical composition of the water of the ponds depends primarily on the chemical cha-
racters of the soil which it crosses and of the vegetation which recovers them. In general water of
savanna is richer and less acids than water emerging from the forest, but the risks of pollution by
the sediments are greater (gullying, erosion). The richer the crossed grounds are in rock salt and the
more water have then a strong natural productivity, because the proliferation of the phytoplankton
and some higher plants.

swamps

source
land limit

land limit

Figure 25. Identification of potential water supplies (A, K), drainage options (C, D, L, M, E,
F), individual valleys (M level compare to D), comparison of the various good sites for the
installation of ponds (IG, GH, ON), vision of the bottoms (CIRAD).


Table VII. Topographical features for ponds.
Slope in lenght Slope transverse Pond Cost
High High None Too high
High Weak Diversion Reasonable
Weak High Dam Reasonable
Weak Weak Sunken High

II.3. THE TOPOGRAPHY
A viable construction of pond is possible only if the topography allows it. One of the general
principles is to minimize the costs. For that, it is good that the water supply of the ponds is done by
gravity, just as draining. Moreover, the dikes must be able to be built without much displacement of
soil. Topography related, as we said it, to the forms and élévation of the considered land. One will
speak thus about a flat ground or a rough ground, from a narrow and boxed or broad valley… Topo-
graphy will determine the possibility to build ponds, their surface and their number (Table VII above).
Once a zone is chosen, according to water and of the soil, it will be necessary to check various
topographic parameters to confirm the potentiality of installation. It will be necessary to measure the
zone, the slope, the elevation and the distance according to the source from water, the best way to
supply the basins, the simplest way for the drainage. One will be able also better to thus apprehend
the places to install the pond(s) (Figure 25, p. 53). The choice of the site for the construction of ponds
in rough grounds will have to be done by having in mind the fact that future excavation will be able
to balance approximately with the embankments.
Moreover, the difference of height should be able to be developed in the supply and water gra-
vitating draining of the ponds. The supply of water by gravity largely simplifies the installation of the
ponds according to topography. The source of water must be located higher than the pond so that
water can run out of itself in the pond (Figure 26 below).
A soft slope will allow a good water run-off. This slope must have between 1 and 3 % (i.e. a dif-
ference with horizontal of 3 cm for a length of 100 cm). If the slope is too strong, one will have a too
important runoff of water. If it is too weak, a dam will be necessary to store water, which will involve
sometimes heavy additional work. Without slope, there is no flow of water, which will not allow drai-

Figure 26. Water supply by gravity.


2. SELECTIONS
ning of the pond (Figure 27 and Figure 28, p. 55).
To calculate a slope is rather simple and requires few materials (Photo A, p. 56, Figure 29 and
Figure 30, p. 57). It is expressed as a percentage. A stake in top and a stake in bottom of the slope are
placed. One horizontally tightens a rope between the two stakes using a plumb level. In absence of
level, a bottle filled with water can make the level. This device is particularly practical, since it makes
it possible to proceed quickly, even on an unequal grassy ground, and with a sufficient precision

A. Low slope (1 to 3%)
Suitable

B. No slope
How to empty the pond ?
Unsuitable

Break of the dike

High pressure

C. Strong slope
Unsuitable

Figure 27. Type of slopes and constraints.

A B C

Figure 28. Hill slope. A: Too high; B: Too high on one side, the second side if favourable;
C: The two sides are favourables.


(the maximum error is lower than 6 cm by 20 m of distance). It requires a team of three people. An
observer installs a stake with the starting point A whose site is marked and maintains the rope on
the graduation corresponding to h. The observer in B also maintains the rope against the same
graduation, then upwards moves the cord on the second stake or to the bottom of the slope, until
the person placed at the center indicates that the plumb level is with horizontal with the well tended
rope. If one does not have a mason level, a water bottle can be enough. There H is known. It is then
possible to measure the H-h difference. The slope P in % will be then:

P = (H-h) x 100 / D

With D = distance between has and B.

II.4. THE OTHER PARAMETERS
II.4.1. THE ACCESSIBILITY OF THE SITE
A good fishfarmer will daily control the pond. At least, he comes each day to survey the pond,
he gives to eat per day to his fish if necessary. Each week, he reloads the composts, he cuts grasses
on the dikes… It is necessary thus that the pond is not too far from the house of the fishfarmer and
that there are no barriers between the pond and the house (river in rainy season, for example). It is
advised to live more close as possible to its pond to supervise it against the thieves (Figure 31, p. 58).
II.4.2. THE POSSIBILITY OF BUILDING WITH LOWER COSTS
It was already seen that one will not build a pond where the slope is very strong because the
downstream dike should be very large and thus expensive for a pond of reduced surface. For each
work, one compares the required effort with the benefit which one can draw.
If there are the choice, one thus will prefer an open site at a site full with tree trunks which are ne-
cessary to be remove with all the roots. One also will choose a ground without rocks or large stones.
II.4.3. THE PROPERTY LAND
It is a question of knowing the owner of the site on which will be established the future series of
ponds. One will have to make prospection. One
of the solutions is to require to the villagers to see
by themselves which are the sites of proximity.
Then, to evaluate the various sites according to
the criteria above.
In margin of the ponds, the maintenance or
the plantation of the trees and other plant spe-
cies will make it possible in very broken ground
not only to protect the grounds against ero-
sion, but also to consider the exploitation of the

Photo A. Measurement of a slope (DRC) [© Y. Fermon].


2. SELECTIONS
ground on profitable way by considering by anticipation the various components of an integrated
fishfarming with the other production of the rural world (grass for bovines, fruits as food or fertilizers
in the ponds, zones really water full for cultures like rice,). The cleansing and the drainage of water in
the majority of the swamp zones being difficult, these last will have to be selected for the construc-
tion of fish ponds by having in mind this constraint likely to encumber the costs with exploitation in
the future.

Observer at the Observer at the
back front

Keep both ends of the rope at the
same height

Observer at the center

Figure 29. Measurement of a slope: Device.

D

A B

stake rope level
h
stake
H

H-h

Figure 30. Measurement of a slope: Calculation.


Figure 31. Example of location of a pond in relation of the house.

Ö The site selection have to take into account:
Ö The water: quantity and quality;
Ö The soil: impermeable;
Ö The topography: Weak slope and zone of emergence of sources.


Chapter 06
CHARACTERISTICS OF THE PONDS
Once the choice of the villages then sites of installation of the ponds made, it now acts to set up
the ponds (Figure 32, p. 60).
The fish production is based on the use of earth ponds which contain freshwater, renews it, and
allows the storage, the farming and the harvest of fish. The construction of the ponds and associa-
ted structures include adapted preparations and work, essential for the success of the exploitation.
Moreover, the ponds must be inexpensive to build, easy to maintain and specific to ensure a good
management of water and fish.

I. DESCRIPTION
A fish pond is not very deep a water place, used for the controlled farming of fish. IIt is adapted
to be easily and completely drained.
It consists of (Figure 33 and Figure 34, p. 61):
9 The plate which is the bottom of the pond.
9 The dikes which surround the pond and are the walls making it possible to contain water. So
they must be solid to resist to the pressure and impermeable.
9 The intake which is the structure to collect a quantity of water to feed the pond.
9 The emissary who is a river or a channel which allows the drainage of the pond.
9 The channels, which bring or evacuate the water of the pond:
• The water arrival or supply channel which makes it possible to bring collecting water to
the pond.
• The draining channel or evacuation which is the work allowing the drainage towards the
emissary.
9 The devices of regulation, which control the level of water or its flow through the pond, or
both:
• The water inlet which is the device designed to regulate the water flow towards the pond
and which protects water from the floods.
• The water outlet preferably a monk which allows the control of the level of the water and
evacuation of the pond.
9 The outfall or overflow which allows the evacuation of the water excess of the pond and
ensures the safety thus of it.
9 The filters, if necessary, which prevent animals and particles to come in and leave the pond
9 The fence which surrounds the pond and avoids the undesirable visitors.
9 Other structures of protection against ichtyophagous birds, if necessary.
9 The access ways and roads, which skirt the pond and make to reach it.

II. TYPES OF PONDS
The piscicultural fresh water ponds differ according to the origin of water supply, the way of
draining them, materials and processes of construction and, finally, the methods of fishfarm. The
characteristics of the site in which they are built determine usually their characteristics.
One can classify the ponds according to:
Ö The water supply.
Ö The drainage systems.
Ö The building materials.
Ö The type of use of the pond.


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia

61/4 - 91/4 months
follow-up of the
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining

Figure 32. Setting of fish pond: 3. Ponds.


3. PONDS
Regarding the use of the pond, it is certain that the same pond can be used for various uses
according to the moments and the evolution of the structure installation.
One will find:
9 Spawning ponds for the production of eggs and small fry;
9 Nursery ponds for the production of larger juveniles;
9 Brood ponds for broodstock rearing;
9 Storage ponds for holding fish temporarily, often prior to marketing;
9 Fattening ponds, for the production of food fish;
9 Integrated ponds which have crops, animals or other fish ponds around them to supply
waste materials to the pond as feed or fertilizer;

In this case, only the ponds usable for the subsistence fishfarming and which are the most viable
ponds, will be considered. The principal characteristic will be that they are entirely drainable with
running water available all the year. We will not take into account, ponds collinaires supplied with
streaming or rainwater and the ponds of resurgence supplied with water of the ground water.
We will focus the work on two types of ponds fed by a river:
9 Barrages ponds.
9 Diversion ponds.

Outside slope Pond
of dike

Outlet Inside slope
of dike Inlet
Monk
Water
supply
Pond
Crest
Diker

Figure 33. Main components of a pond.

Outside slope Crest Inside slope Water Water
Inlet
of dike of dike level supply
Monk
Outlet
Dike Pond

Figure 34. Cross section of a ponds.


II.1. BARRAGE PONDS
The barrage ponds are ponds through which pass all the water coming from the source (Figure
35, p. 64).
On a small river, one can block itt so that the water mass retained by the dam made a pond. In
front of the dam, one installs a monk to drain the pond. One or more outfalls are expected to drain
the excess of water in case of raw or strong rains. The outfalls must be able to evacuate even the
strongest flooding, if not all the dam may be carrried. The most important point before beginning the
construction of a barage pond is to know the maximum level and the maximum discharge of the river
during the rainy season after a strong rain. On the great rivers which grow extremely in rainy season,
it is preferable to make diversion ponds rather than barrage ponds. In addition to this lack of control
on the water flow which enters the pond, one cannot either prevent the fish which live upstream of
the river to enter in the pond. One cannot either put nets on the outfalls to prevent fish escape when
the outfall work. Net may be blocked with sheets, branches and mud in suspension in water. Water
will go up and can break the dike.
One cannot correctly control the amount of water which crosses the pond: there are thus many
risks of flood (food and fertilizer, fish loss when the flow of the river is important).

II.2. DIVERSION PONDS
Contrary to the barrage ponds, which retain all the water of the stream, the diversion pond use
only part of water (Figure 36, p. 65). These are ponds through which passes a portion of water from
the source and not all. The entry and exit of water in the pond are controlled.
One thus will deviate part of the stream in a supply channel which will bring water to the ponds.
The intake on the stream is usually built in front of a small dam of deviation. This dam ensures a
constant water level in the supply channel. All the surplus of water which is not need passes by the
outfall of the dam. The ponds supplied with a diversion channel can be built in parallel or series.
The diversion ponds in derivation of the bypass type are built on the slopes of a valley and are
primarily made up by three dams. These ponds are in general inexpensive, without risk of flood and
well drainable.

II.3. COMPARISON
It is important to remember the following points:
Ö Better control of the water supply means easier management of the pond, e.g. when fertilizing
the water and feeding the fish.
Ö Better drainage also means easier management of the pond, e.g. when completely harvesting
the farmed fish and when preparing and drying the pond bottom.
Ö A regular shape and the correct size makes a pond easier to manage and more adaptable for
particular purposes.
Ö The choice of a particular type of pond will largely depend on the kind of water supply available
and on the existing topography of the site selected.
Practically, in spite of a higher cost, the increasingly intensive integrated management of the
production of fish, will be better with diversion ponds (Table VIII, p. 63). Moreover, it will not be possible
to extend the number of ponds with a barrage pond. This is important because that avoids blocking
water of rivers which is also used by the villages located downstream. That can make it possible to
avoid conflicts sometimes violent one.

Ö Diversion ponds supplied with water by gravity are the most adequate approach
proposed here.


3. PONDS
Table VIII. Advantages and disadvantages of the barrage and diversion ponds.

Type Advantages Disadvantages

• Dikes need to be carefully anchored be-
cause the risk of break down in case of floo-
ding.
• Need for a spillway and its drainage which
be costly.
• Simple to design for small stream. • No control of incoming water supply (quan-
• Construction costs relatively low unless tity, quality, wild fish).
Barrage • Cannot be completely drained except when
there are flood defence problems.
pond* incoming water supply dries out.
• Natural productivity can be high, according
to quality of water supply. • Pond management difficult (fertilization, fee-
ding) as water supply is variable.
• Irregular shape and size.
• Sociological problems due to possible
water retention towards the people living
downstream.

• Easy control of water supply. • Construction costs higher than barrage
ponds.
•Good pond management possible.
Diversion • Natural productivity lower, especially if built
• Construction costs higher on flat ground.
pond** in infertile soil.
• Can be completely drained.
• Construction requires good topographical
• Regular pond shape and size possible. surveys and detailed staking out.

* If the barrage pond is built with a diversion channel, some of the disadvantages may be eliminated (controlled water supply, no
spillway, complete drainage, easier pond management), but construction costs can greatly increase if the diversion of a large water
flow has to be planned.
** Relative advantages will vary according to the arrangement of the ponds, either in series (pond management is more difficult) or
in parallel (both water supply and drainage are independent, which simplifies management).

III. CHARACTERISTICS
III.1. GENERAL CRITERIA
According to the needs, it will be possible to build a series of ponds with a management in
shifted with shifted sowing, which allows monthly harvests, that is regular harvests during the year.
Always with an aim of limiting the amount of work and the costs on the one hand, and of optimi-
zing the availability out of water on the other hand, it will be necessary to lay out the basins according
to topography. The development of a suitable site is consequently a complex exercise.
A positioning in terraces makes it possible to arrange a surface much more important of ponds
and to better keep water (Figure 37, p. 66). While seeking to position the downstream-dikes across the
flow of water in the basement, it increases the availability of storage water of the site.
A overall design of a site is essential to use surface as well as possible, the drop between the
intake and draining and the availabilities of water. A provision of the ponds to the current does not
maximize suitable surface (B): Surface in green is not used. This flow is carried out parallel to the
water course. On the other hand, in the diagram (C), water is blocked in its flow perpendicular to
the water course since all the ponds are on the same level. More water will then be stored in the
basement above the plans of ponds. It will be available to fill the ponds again or to limit the losses
during the dry season.


Stream

Spillway and overflow

Outlet

Inlet to pond

Dam

Larger stream

Water intake

Outlet

Diversion channel
Dam

Figure 35. Examples of barrage ponds.


3. PONDS

Outlet

Larger stream

Pond
Pond

Pond Diversion channel
Pond

Inlet

Larger stream

Diversion channel

Outlet
Pond
Pond
Pond

Pond

Pond

Inlet
Pond

Figure 36. Examples of diversion ponds.


Water supply Water supply
channel channel
Stream Stream Stream

Equidistant
curve level

Drain channel

A B C
Figure 37. Disposition of ponds in relation to the topography (CIRAD).

III.2. POND SHAPE
For an equivalent water surface, one will seek the shape of pond which minimizes the overall
length of dam (Figure 38 and Table IX below). For a pond of the same dimension, the overall length
of the dike increases regularly when the shape of the pond deviates gradually from the square to
become more elongated. Meanwhile, the costs of construction increase. The dikes which separate
the ponds (intermediate dikes) are narrower than the downstream-dike. The square form extend the
downstream-dike (A). A too elongated rectangular form reduces it, but elongate in an important way
the intermediate dikes (C). Moreover, if one wants to keep the same slope to guarantee a good drai-
ning, it will be necessary to dig more deeply. These two forms are not optimal (A and C). On a regular
ground, the shape of pond which will require less work is rectangular but is not too much elongated
(B). It is the form which will be used preferentially. In general, the rectangular ponds have a length
approximately twice higher than their width. It is, also, better to use a standard width for the ponds
planned for the same use.
In several cases, it can be easier and more economic to adapt the shape of the pond to existing
topography (Figure 39, p. 67).

Table IX. Differents shape of a pond of 100 m2.
Pond shape Width (m) Length (m) Dikes length (m)
square 10 10 20 + 20 = 40
7 14.3 14 + 28.6 = 42.6
rectangular 5 20 10 + 40 = 50
2 50 4 + 100 = 104

Water supply channel

A B C

Intermediate dike Downstream dike

Figure 38. Optimization of the surface / work (CIRAD).


3. PONDS
III.3. ACCORDING THE SLOPE
The orientation of the ponds will vary de-
pending on the angle of the slope to minimize
earthworks (Figure 40 below).
9 Slopes of 0.5 to 1.5%: The length of
the rectangular ponds must be perpendicular
to the level lines. This means that ponds must
be oriented in the direction of the slope to the
Dike bottom follow the natural slope and is not ne-
cessary to dig the deepest part.
Figure 39. Example of pond whose shape is 9 Slope greater than 1.5%: The length
adapted to the topography. Here, only two of the rectangular ponds should be parallel to
dikes are needed. the level lines. This means that ponds must be
perpendicular to the slope. More the slope in-
creases, more ponds must be reduced.

I = Inlet - O = Outlet
101.6
20 m
I 101.2
10 101.6
1.2 O I 101.2 20 m
O 100.8
10
100.8 O I
1.0 100.4
100.4
O I
100.0 100.0 O I
10 20
0.8 m 99.6
99.6
99.2
10 99.2
0.6

Slope of 1 % Slope of 3 % Slope of 5 %
Figure 40. Disposition and shape of ponds according the slope.

III.4. LAYOUT OF PONDS
When one wants to install several ponds, there are two possibilities for positioning relative to
each other (Figure 41 below):
9 In series: ponds depend on each other for their water supply, the water running from the up-
per ponds to the lower ponds. This system has the advantage of limiting the number of draining and

I = Inlet
O = Outlet
Water supply
I
O I I I I
I
O O O O
O
I
Drain
O
I O

A B
Figure 41. Layout of ponds. A: In series; B: In parallel.


supply channels of the ponds. However, the fact
that it is the same water which passes in all the
ponds can bring problems as for the propagation
of diseases. Indeed, if a pond is contaminated,
the risk of contamination of the others and to lose
all its production is important. There will be also
problems during drainings of the ponds. The re-
quired slope is also more important in total.
9 In parallèle (Photo B, p. 68): The ponds are
independent from each other, each one being
supply directly from the supply channel. Wa-
ter is not re-used after having crossed a pond.
At contrario of ponds in series, it is possible to
isolate without problems each ponds, and thus
Photo B. Example of rectangular ponds in to limit the risks of contamination. Drainings are
construction laying in parallel (Liberia) done independently and the slope is the same for
[© Y. Fermon]. all the ponds.

III.5. SIZE AND DEPTH OF THE PONDS
The ponds are characterized by their size, their form and their depth. We saw in au paragraphe
II.1, p. 45 the calculation of the surface and the volume of a pond.
III.5.1. THE SIZE
The individual size of sunken ponds and diversion ponds can be decided upon by the farmer,
considering the following factors (Table X and Table XI below):
9 Use: A spawning pond is smaller than a nursery pond, which is in turn smaller than a fatte-
ning pond.
9 Quantity of fish to be produced: A subsistence pond is smaller than a small-scale commer-
cial pond, which is in turn smaller than a large-scale commercial pond.
9 Level of management: An intensive pond is smaller than a semi-intensive pond, which is in
turn smaller than an extensive pond.
9 Availability of resources: There is no point in making large ponds if there are not enough
resources such as water, seed fish, fertilizers and/or feed to supply them.
9 Size of the harvests and local market demand: Large ponds, even if only partially harves-
ted, may supply too much fish for local market demands.

Table X. Size of fattening ponds.
Type of fishfarming Area (m2)
Subsistence 100 - 400
Small-scale commercial 400 - 1000
Large-scale commercial 1000 - 5000

Table XI. Resource availability and pond size.
Small pond Large pond
Small quantity Large quantity
Water
Rapid filling/draining Slow filling/draining
Fish seed Small number Large number
Fertilizer / feed Small amount Large amount
Small harvest Large harvest
Fish marketing
Local markets Town markets


3. PONDS
Table XII. Characteristics of shallow and deep ponds.
Shallow ponds Deep ponds
Water warms up rapidly Water temperature more stable
Great fluctuations of temperature Less natural food availabl
Greater danger from predatory birds Difficult to capture fish in deep water
Strong, high dikes needed
Greater growth of water plants
Smaller dikes needed

50 cm 150 cm

Figure 42. Maximal and minimal depth of a pond.

In the situation of production fishfarming, one will choose ponds having a maximum of
surface of 400 m2.
III.5.2. DEPTH
The fish ponds are generally not very deep. Their maximum depth does not exceed 1.50 m
(Table XII and Figure 42, p. 69). The lower part should have at least 0.50 m in order to limit the growth
of the watery plants. Deeper ponds are of a construction much more expensive because the volume
of the dams increases quickly with the depth of the pond.
However, it is sometimes necessary to use deeper ponds. In the dry areas, to store enough water
to have in dry season for fish is essential.

III.6.DIFFERENCES IN LEVELS
In all the cases, there are some rules which it should not be neglected if one wants to have ponds
easily manageable and completely drainable, supplied with gravity (Figure 43, p. 70).
¾ Water flows down from the highest to the lowest point (A).
¾ The water surface in a pond is always horizontal (B).
¾ The pond bottom should be above the water table at harvest (C).
¾ The bottom of the main water intake should be below the minimum level of the water source (D).
¾ The bottom of the feeder canal should be at or above the maximum pond water level (E).
¾ The pond inlet should be located at or above the maximum pond water level (F).
¾ The start of the pond outlet should be at the lowest point of the pond (G).
¾ The end of the pond outlet should be at or above the water level in the drain (H).
¾ The end of the drain should be at or above the maximum water level in the natural channel (I).


A B C

Water intake Water supply channel Inlet
Inlet

D E F

Outlet Drain channel
Sream
Drain channel

G H I
Figure 43. The different points for the management of water by gravity.
The explanations are given in the text.

In the case of a diversion pond fed from a stream through a main water intake and a feeder canal,
it is easy to determine the difference in level ( (x) (cm) equired between minimum water level at the
main intake and maximum water level at the end of the drain (Figure 44, p. 70). One preferably consi-
ders a pond a depth of 150 cm. It will be necessary to add there the difference in level necessary
between the outlet of the drainage device of the pond and the maximum water level in the channel
of draining (b) and the difference in level necessary between the water supply channel of the pond
and the maximum water level in the pond (c) as well as the value between the entry and the exit of
the drainage device of the pond (e).
1
1a 1b 2 3 4 5 6 7 7a 7b 8 9

c a
d
x x
b

1: Upstream - Water level: 1a: minimum - 1b: maximum
2: Main water intake: same level than upstream 6: Top of dikes
3: End of intake channel 7: Pond outlet - 7a: Start - 7b: End
4: Pond inlet 8: Drainage channel
5: Maximum water level in the pond 9: Downstream - Maximum water level
x = The difference in level required between the minimum water level at the main intake and the maximum water level at the
end of the drainage channel
a = The difference in level required between the top of the dikes and the maximum water level in the pond
b = The difference in level required between the end of the pond outlet and the maximum water level
in the drainage channel
c = The difference in level required between the pond inlet and the maximum water level in the pond
d = Maximum depth of the pond (150 cm minimum)

Figure 44. Level differences.


3. PONDS
x > 150 + b + c + e

This minimum of difference in level is essential to have completely drainable ponds.

IV. SUMMARY
Ö We will choose:
Ö Diversion ponds,
Ö Rectangular,
Ö Arranged in parallel,
Ö Size of 100 to 400 m2,
Ö Supply with water by gravity.

The ponds will thus be laid out according to a diagram like that indicated on Figure 45 below.
Examples are presented Figure 46, p. 72.

Stream

Water
Stream used as supply
diversion channel

I
O

I
O

I
O Water supply
channel
Water supply I
channel outflow in O
the stream
I
O
O I
I = Inlet
O = Outlel

Figure 45. Classical plan a diversion ponds.


Stream

Natural diversion
channel

Water supply
channel

A

Stream Water supply
channel

Water supply
channel

Diversion
channel

B
Figure 46. Examples of diversion fishfarm.
• Water supply by a stream
• One (A) or two (B) row(s) of ponds in parallel
• A natural diversion channel
• Optimal water control


Chapter 07
THE CONSTRUCTION OF PONDS
Once the site is chosen, it acts to carry out the construction of the ponds and the associated
structures (Figure 47, p. 74). As we saw in the previous chapter, we will be interested here only in di-
version pond which is the preferential type to use, but it is clear that these steps are the same ones
for another type of pond. It is, however, important to perform this work in dry season.
To build ponds of quality, it is necessary to complete work by steps and in a certain more or
less strict order which is briefly described here for a diversion pond of the bypass type.

1. Laying out plan
2. Cleaning of the site
3. Water supply channel
4. Draining channel
5. Staking out the pond
6. Building the dikes
7. Pond bottom drain laying out
8. Building inlet, outlet and filtration
9. Décantation pond
10. Other structures: Erosion fight, biological plastic, fence
11. Filling in water and test

I. THE DESIGN PLAN
With this stage, one studies one or more possible localizations of the ponds. A first selection
is taken minimizing work compared to clear surface. The design is progressive: The assumptions
formulated on the filling and the diversion of water are progressively evaluated as to the completion
of construction.
The criteria which will be observed throughout installation are mainly:
9 Rise of ground water;
9 The tightness of the dam downstream dike;
9 The behavior of overflows and monks during the flood;
9 The feasibility of the work;
9 Interactions that develop with the surrounding facilities (bins, gardening).
An initial plan is proposed (Figure 25, p. 53 and Figure 48, p. 75). It is a question of writting mea-
surements of lower slope and of locating on the plan the position of the various structures to be
developed.
Initially, one will partially clean the ground with cutter for a better viewing.
Then, one will proceed to the survey of the site. In a general way, this survey is done methodi-
cally, with a regular spacing between the measure points. Each point is materialized on the ground
using a level stake. A letter corresponding to the same letter on the future topographic chart is
written on the top of the stake. Spacing between the points will depend on the topography of the
ground. If the ground is very undulated, the points will be very closed. The first point can be take on
the position of the collecting point.
The line of greater slope may be determined as it has been show in paragraphe II.3, p. 54. For that,
the highest point will be located, then the lowest. Then one will calculate the slope between these
two points.


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia

61/4 - 91/4 months
follow-up of the
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining

Figure 47. Setting of fish pond: 3. Ponds.


3. PONDS

swamps

source land limit

Staking out
the channel

Staking out dikes
and slopes

land limit

Figure 48. Visualization by picketing of the first plan of possible water supply (A, K), pos-
sible drainage (C, D, L, M, E, F), of differents valley (level of M towards D), (Figure 25, p. 53)
(CIRAD). In red, limite of work.

The line of greater slope makes possible to establish the various structures of the fishfarm so
that they are most functional possible, particularly from the point of view of the drainage and water
sanitation.
The arrangement of the various structures on the topographic map will have to be done by taking
into account the cost of construction and operation of the future farm, safety requirements of work,
and probable future extension of the farm.

II. THE CLEANING OF THE SITE
After having delimited and visualized the future site of the fishfarm, the first work will be to clean
this zone. It is necessary to define in a precise way the concerned zone before starting to clear, then,
to determine the external corners of the surface containing the ponds, which must completely in-
clude the surface occupied by the dikes. One can delimit this zone by stakes out of wooden, ropes or
posts. Once this task is achieved, it is necessary to delimit an additional surface, beyond the dikes,
which will be used as passage and working area around the site. One is then ready to start (Figure
49, p. 76). That start with:
Ö Clear the zone including the dikes of the ponds by removing it of all the vegetation, the shrubs,
the trees (including roots and stocks) and of all the large stones.
Ö Clear the passage and working area around the dikes.
Ö Clear all the trees and shrubs on a area of 10 m around the dikes and the works, around the
access roads and the installations of water supply and drainage.


Delimit an area then
Remove the shrubs
clear it completely,
and the trees on an of
including a zone of
10 m around
passage from 2 to 3 m

Remove all the
vegetation

1 2
Figure 49. Preparation of the site of the pond.
All the grasses have to be cutted as for the culture. All the trees must be cutted and their roots remo-
ved. If roots are left, the pond will eventually seep. The grasses, the shrubs, all organic matters and
the rocks must be removed. One will be able to burn if that is possible. The ground must be very well
cleaned before the construction itself does start. Among the elements to be removed, one will find
(Figure 50 below and Photo C, p. 77):
9 Woody plants (A), where the roots can cause serious cracks in the fishfarm structures like the
devices of water supply and draining.
9 Stocks of trees (B), whose decomposition can weaken the structures by leaving vacuums
in the ground.
9 Large stones and rocks (C), whose extraction can prove to be necessary.
9 Termite mounds and burrows of animals (D), which must be completely removed. Then it is
necessary to fill the hole created with clay.

Tree stump

B
Rocks and stones

Shrubs and trees

C
Termite mound Burrow

A D
Figure 50. Cleaning of the site. A and B: Trees; C: Rocks and stones; D: Animals habitats.


3. PONDS

Photo C. Cleaning of the site. On left: Tree remaining nearby a pond {To avoid}(DRC);
On right: Sites before cleaning (Liberia) [© Y. Fermon].

III. WATER SUPPLY: WATER INTAKE AND CHANNEL
The water supply includes water intake, the main channel and the small canals which bring water
from the main channel to the pond.
The principal water intake are used to regulate overall and to derive the water supply from a pond
or a group of ponds. They have primarily the role to ensure a regular water supply, which may be
regulated according to the present conditions.
The water inlets are settled, if possible, against the water current to prevent the transport of ma-
terial that the river carries, to the ponds. This canal fed in theory by a constant flow, but adjustable,
is made to bring water to the upper part of the ponds built so that their complete draining can be
made whatever the level of water in the bottom of the valley. This condition is very important and
must be strictly respected. In too often cases where it is not, the ponds are just simple diverticula
of rivers whose flood demolish the dike and where the fish enter and leave easily. One makes some
surveys to see whether it does not arise particular difficulties (presence of rocks in particular).
The main elements of a water intake are:
Ö A diversion structure being used to regulate the level of the watercourse and to ensure that it is
sufficient to feed the water intake without drowning.
Ö A device of regulation of the level of entry (and flow) inside the structure itself, being used to
regulate the water supply of the ponds; such a device is generally connected to the transport of
water structure;
Ö A structure of protection of the entry, for example stilts to prevent any deterioration of the water
intake due to the debris.
One will use an open or free level water intake in which the levels of supply are not controlled and
where the water catch functions under all the conditions of flow. This system is simple and relatively
cheap, but it generally requires a reliable water supply which does not vary too much.


The important points to take into account are the following (Figure 51 and Table XIII below):
Ö The levels of the source of water supply (river, small river…) related to the water supply structure
and the ponds themselves.
Ö The depth to which one wishes to collect water (surfaces, low or on all the depth of the water
source).
It will have to be made sure that the water level in the supply source is always sufficient to take
water with the desired depth. It also should be made sure that the water intake is not likely to be
drowned.
The broader the water intake is, the less the pressure loss will be strong when water runs to-
wards the ponds. This factor can have importance in the event of very weak load.
In the majority of the cases, however, the water intake has approximately the same width as the
supply channel which is connected to him. The size of the supply channel is fixed according to the
desired flow. If the supply channel is particularly broad, or if one wants to increase the pressure loss
on the level of the water intake (for example, if the external level of water is definitely higher than
that necessary in the supply channel), the water intake can be narrower than the supply channel.
In general, a narrower intake is easier to regulate. For that, one can install structure simple to build.
After selecting the water intake, the supply channel which will bring water into the ponds have
to be arranged (Figure 52, p. 79). This channel has a very weak slope and must be able to bring water
throughout the year. One chooses the layout of the channel by stakes a level line on the basis of the
base of the water intake until the site where the ponds will be built. Practically, after having esta-
blished the layout of the level line, one adopts a definite location according to the ground.

A B C D E F

Stream Main water The water level decrease Inlet of the pond Pond
supply with the distance
A: Minimum-maximum water level in the stream and in the first part of the channel
B: Charge loss
C: Minimum-maximum water level in the last part of the channel after the charge loss
D: The level of the inlet of the pond have to be lower than the minimum water level in the channel
E: The maximum water level have to be check to avoid flood
F: The release of the inlet is at 10 cm over the maximum water level of the pond
Figure 51. Water levels differences.

Table XIII. Diversion structures to control stream water levels.
Type of stream Structures required
Dikes in earth
Flow less than 10 liters/ Of diversion
Wood/ropes/clay
Small secund Not to be submerged
Wooden fence
No significant flood conditions No need -

Water flow at least twice the Of diversion Wood or stones dikes,
flow required To rase water level adjustable
Large
Significant flood conditions No need -


3. PONDS

Staking out

Final layout Water supply channel

Figure 52. Setting of the water supply channel.

It is always necessary to avoid giving a too strong slope to the channel and providing if neces-
sary, stones or concreted falls. Then, one carries out the digging and the sloping of the channel.
Remember that the channel should be dug dry. The method consisting in digging a channel as water
penetrates there, is to be avoided because it systematically results in giving a slope too much strong
to the bottom of the channel.
The channels without sealing surface have most of the time a cross section of trapezoidal form,
defined by the following elements (Figure 53 below):
9 The width (b) of its bottom (or ceiling) horizontal;
9 The slope (z/l) of the side walls;
9 The maximum depth of water (h);
9 The revenge (f) allowing to avoid any overflow.
The dimensions of the channel are indicated in Table XIV, p. 80.
It is essential that the current speed in the channel does not involve the erosion of its walls.
The maximum speed of water varies with the nature of the ground: 0.15 m/s in the fine ground and
1.00 m/s in stones.
If one cannot follow the level line for an unspecified reason and that one must reduce the level of
the channel, it is necessary to envisage an oblique fall or or a pipe, but one should not in no case give

Water level
Slope z/l (1.5/1 ou 1.5:1)
f

h l
(l = 1)

z
(z = 1.5)
b

Figure 53. Transverse profile of the channel. Measure and slope of sides.


Table XIV. Channel dimensions.
Small farm Medium farm
A few l/s 20-50 l/s
Bottom width 20 to 30 cm 50 cm
Water depth 20 to 40 cm 60 to 80 cm
Side slope 1.5:1 1.5:1
Top width 60 to 100 cm 150 to 180 cm
Bottom slope 0 1 ‰ (1 cm per 10 m)

to the channel a too strong slope. So, despite these precautions, the water of the channel is turbid,
it should be provided on the water course of the mud tanks or conceived widenings in such way that
the current velocity is enough low there, to allow the deposit of the suspended matter.
After the last checks of the definite location, one can carry out the earthwork of the dry channel,
while starting where one wants, according to the needs for the moment. This operation is done in
three times (Figure 54 below):
1. First, to dig the central part with distant vertical walls of a width equal to the width of the bottom,
then one adjusts the slope longitudinally along the bottom, and one proceeds to the cut of the slopes
(sloping).
2. Be carefull to leave in place (in the axis or on the edges) the stakes whose tops must be used

Cnttre line Centre line Cut out sides of channel

Leave 10 Dig out
cm of earth remaining
at the 10 cm of earth
bottom Bottom width Bottom width Bottom width

Mark the Move the rope
line of the out to the slope
channel stakes
with centre, Cut out sides of
slope and Rope channel
bottom Leave
stakes sections of Remove
earth sections of
Rope earth

Stretch a Check
Remove centre cross-section
rope along and bottom
the bottom with wooden
stakes gauge
stakes

Masons level

Stakes Final channel
bottom

Figure 54. Channel digging.
Photo D. Channel during the digging (Liberia) [© Y. Fermon].


3. PONDS
as reference mark for the depth and to reject the excavated materials downwards in order to avoid
a possible overflow during floods.
3. One adjusts the slope longitudinally to the bottom.
When, in certain places of the course, the channels must be deepened, the same gauge is used
to check as the constant width of the ceiling and the regular slope of the banks was respected
strictly, in the major part of the channel.
Conversely, when the channel must pass by some high points and hillside, the depth of the ear-
thwork will be lower and the installation of a bench on the side of the channel is necessary. This one
will be built out of perfectly compacted ground and the peak, of a sufficient width, will have to reach
everywhere the same level above the wetted cross section.
The installation of the water falls intended to bring back the slope of the channel to the accep-
table maximum, must always be made before the first setting in water, in order to eliminate all the
risks from erosion. On the other hand, the installation of the overflows, the settling basins and the
ditches of guard for the drainage of rain, if they are necessary, is less urgent.
To finish, it should be noted that the process which consists in digging a channel (backwards) by
small sections starting from the river until the sufficient depth so that water runs there, systematically
leads to give too much slope to the channel. This process is not dadvisable.

IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE
The site and the layout of the channel of draining are in general easier to determine (Figure 55
below). The ponds must be able to be emptied throughout the year without remaining there any
water pool. For that, it is necessary that the bottom of the channel of draining is much lower than the
bottom of the pond (Figure 56 below). This channel is built, generally, once the pond finished. Howe-
ver, it is included here because the way of carrying it out is identical to that of the supply channel.
To take the bed of the valley as channel of draining is risky. Indeed, if during the floods, the
water level in the valley is higher than the bottom of the pond, one will not be able to use the bed of
the valley like channel of draining. If, on the contrary, this water level is permanently lower than the
bottom of the pond, one will be able to use the bed of the valley like channel of draining. It is also
preferable to set up a channel of drainage around the zone of the ponds. Now, the following stage
will be to fix the site of the ponds on the area between the supply channel and the position of the
channel of draining.

Water supply channel

Location of the pond

A Lower level than that of the pond

Drain channel

B Sometimes upper than that of the pond
Figure 55. Setting of draining channel. Figure 56. Level of draining channel.


V. THE PICKETING OF THE POND
On the area delimited by the draining and
water supply channels, one can now delimit the
ponds. This operation is called the picketing or
staking. It must allow to represent the site of the
dikes as well as dimensions and the heights of
the dikes with stakes. It will thus be necessary
to respect, thereafter, these dimensions during
work (Figure 57 below and Photo E opposite).
The staking is done using stakes which
must have a sufficient height to allow spoil or
fill later without risk to discover the buried ends
or to cover the air ends. One will on the whole
have 4 rows of pegs for the main dike and the 2
side dikess and 3 for the upstream dike. These
stakes will be spaced from each other of 2 m. A
spacing between the rows of pegs will be func- Photo E. Stakes during the building of the
tion of dimensions of the dikes. dikes (Liberia) [© Y. Fermon].

Water supply channel Water supply channel

Location of the pond Location of the pond

Drain channel Drain channel

Figure 57. Picketing of the pond and the dikes.


3. PONDS
Intermediate dikes
between neighboring ponds

Upstream

Downstream

Lateral

Peripheral dikes

Figure 58. Cleaning of the zones where the Figure 59. Definition of the different types
dikes will be build. of dikes.

VI. THE CONSTRUCTION OF THE DIKES
It is not enough to dig a hole to have a pond: after having delimited the site of the pond, it is ne-
cessary to build carefully the quite tight dikes around. The dikes are the essential parts of the pond,
on them will depend solidity on the pond, its capacity to retain water…
It should be remembered that it is necessary, initially, to remove the plate of the pond and the
site of the dikes of all the debris which could be there: roots, plants, stones… One also removes the
surface layer of the ground, (i.e. the layer of cultivated ground), where the dam must be built, to avoid
the water escapes through the base of the dike when the pond is underwater. Most of the time, one
forgets to strip the ground before the construction of the dikes. This almost always causes im-
portant water escapes and consequently, an increased requirement of water (Figure 58 above).
For a diversion pond, one distinguishes (Figure 59 above):
9 The upstream dike parallel to the supply channel,
9 Lateral dikes, perpendicular to the upstream dike and the main dike and supporting on their
walls (berms), the pressure of water from two nearby ponds, and

Crest

1 m

Height

1 m
Extern

Intern

2 m 1 m 1 m

Side Base

Figure 60. Description and proportion of a dike (of 1 m high).


9 The main dike, that downstream, which supports of its slope upstream the greatest pres-
sure of water of the pond. The latter must be thickest and highest.
A dike comprises five principal parts (Figure 60 below):
9 The foundation or bases,
9 The body,
9 The bench or top,
9 The slopes,
9 The height.

Any dike must have the following properties:
Ö It must be able to resist the water pressure created by the height of the water mass retained
in the pond (Figure 61 below).
Ö It must be sufficiently high to prevent water from flowing out, which would quickly cause to
destroy it (Figure 62 below).
Ö It must be impermeable, and the infiltrations through the dike must be reduced to the minimum.
If the soil contains a lot of sand, it is advisable to trench in the center, throughout each dike, to
the layer of impermeable ground, in order to replace the sandy and permeable ground by an imper-
meable clay core which goes until the top of the dike. The dikes thus built are tight and more solids.
This technique of anchoring of the dike wich not request too much work is advised for construction
of ponds and whatever the type of soil used for construction (Figure 63, p. 85).
It is generally useless to provide an intermediate dike, which separates two ponds, a solidity
comparable with that of a peripheral dike, insofar as the water pressure is practically equal on both
sides. However, if a pond should be emptied whereas the other remains full, the variations of pres-
sure will be close to those observed on the peripheral dikes, and will have to be envisaged a more
solid construction.
The dimensions of the dikes depend on the surface of the pond. The foundation of the dike is
function of the height of water in the pond. The slope of the embankment is function of the quality
of the soil. It can thus vary from 1 per 3 (that is to say 33 %) for a soft ground to 2 per 3 (66%) for a

Unequal water pressure Equal water pressure

Stronger dike Dike may be less
needed strong

Figure 61. Pressure difference on a dike.
Strong rainfall Strong rainfall
Dikes break down
High dikes
Water go inside the pond

Fish escape
A B
Figure 62. Dikes. A: Good high; B: Dikes too small.


3. PONDS
soil of better bearing pressure. The bench or top
of the dike must have a width higher than 1 m to
allow later handling of the seine during fishings.
An establishment of the dike starts with the es-
tablishment of the foundation.
The downstream-dike which surround the
fishfarming site is the object of a pressure exer-
ted by the water of the ponds. Water saturates
the soil in bottom with the dike (Figure 64, p. 85).
The downstream-dike must be made conse-
quently to avoid any infiltration. On the sandy
soils, it must have a base broader than on the
argillaceous soils.
When water, in its way, meets a ground wa-
ter located low, the water of the basement of the
Figure 63. Digging of the cut-off trench for pond is in balance with the expanse of water
clay core. since it lost its pressure. In this successful case,
there is no more infiltration once the water-log-
Clay core lowers saturation line ged soil with water.
Hydraulic The calculation of the height of the dam to
Water line gradients be built should take into account (Figure 65 op-
8:1 posite):
4:1
8:1 9 Desired depth of water in the pond.
9 Freeboard, i.e. upper part of the dike
which should never be immersed. It varies from
25 cm for the very small ponds in derivation to
100 cm (1 m) for the barrage ponds without di-
Clay core version canal.
9 The dike height that will be lost during
Figure 64. Clay core and saturation of the
settlement, taking into account the compres-
dikes.
sion of the subsoil by the dike weight and the
Settlement (dike heigh lost) settling of fresh soil material. This is the settle-
Freeboard (25 - 100 cm)
ment allowance which usually varies from 5 to
20 % of the construction height of the dike.
Accordingly, two types of dike height may be
defined (Figure 66 opposite):
Depth of water
Ö The design height DH, which is the height the
dike should have after settling down to safely
Figure 65. High of a dike. Depth; Freeboard; provide the necessary water depth in the pond.
Settlement. It is obtained by adding the water depth and the
freeboard.
Ö The construction height CH, which is the
(15%) height the dike should have when newly built
SH and before any settlement takes place. It is equal
FB (30) to the design height plus the settlement height.
The construction height (CH in cm or m) sim-
CH
{153} DH WD ply from the design height (DH in cm or m) and
(130) (100) the settlement allowance (SA in %) as follows:

CH = DH / [(100 - SA) / 100]
Figure 66. High of the structure (definitions
and example in the texte).


If the maximum water depth in a diversion pond of medium size is 100 cm and the freeboard
30 cm, the design height of the dike will be DH = 100 + 30 = 130 cm. If the settlement allowance is
estimated to be 15%, the required construction height will be:
CH = 130 / [(100 - 15) / 100] = 130 / 85 = 153 cm.
A dike rests on its base. It should taper upward to the dike top, also called the crest or crown.
The thickness of the dike thus depends on:
Ö The width of the crest; and.
Ö The slope of the two sides.
The dike must make 4 m at the base for a minimum 1 m of height, globally. The slope of the
dike at the bottom of the slope of the pond is more important to limit erosion and to allow an easier
access to the bottom of the pond (Figure 60, p. 83, Figure 66 and Table XV below). The width of the
top of the dike is related to the depth of water and the part which the dike must play for circulation
and/or transport:
Table XV. Examples fo dimension of dikes.

Surface (m2) 200 400 - 600
Quality of soil Good Fair Good Fair
Water depth (max m) 0.80 1.00
Freeboard (m) 0.25 0.30
Height of dike (m) 1.05 1.30
Top width (m) 0.60 0.80 1.00
Dry side, slope (SD) (outside) 1.5:1 2:1 1.5:1
Wet side, slope (SW) (inside) 1.5:1 2:1 2:1
Base width (m) 4.53 6.04 6.36 8.19
Settlement allowance (%) 20 20 15 15
Construction height (m) 1.31 1.31 1.53 1.53
Cross-section area (m2)
3.36 4.48 5.63 7.26
Volume per linear m (m2)

Crest
(> 1.00 m)
Crest width at least
equals water depth (1.00)

(0.40)

Dry side
slope
Wet side slope {1.5:1}

{2:1}
Water
depth

Clayey soils

Increase as sand increase

Figure 67. Dimension of a dike.


3. PONDS
Table XVI. Expression of values of slope ac- 1 m 1 m 1 m 1 m 1 m 1 m 1 m 1 m 1 m
cording the chosen unit.

Slope 1.5
1 m :
Ratio Pourcentage Degrees 1

1:1 45 100 3:1 1 m 1.50 m
1
1.5:1 34 66 2:1 1.5:

1
1:
2:1 27 50 Axe
2.5:1 22 40 Figure 68. Calculation of the slope
3:1 18 33 of the dikes.
Ö It should be at least equal to the water depth, but not less than 0.60 m in clayey soil or 1 m in
somewhat sandy soil.
Ö It should be even wider as the amount of sand in the soil increases.
Ö It should be safe for the transport you plan to use over it.
In individual ponds, dikes have two faces, the wet side inside the pond and the dry side or ex-
ternal side (Figure 67, p. 86). These two sides should taper from the base to the top at an angle that is
usually expressed as a ratio defining the change in horizontal distance (z in m) per metre of vertical
distance as, for example, 2:1 or 1.5:1. In a dike with side slope 2:1, for each 1 m of height, the base
width increases on each side by 2 x 1 m = 2 m.
The side slopes of each dike should be determined bearing in mind that:
9 The steeper the slope, the more easily it can be damaged;
9 As the soil becomes more sandy, its strength decreases, and slopes should be more gentle;
9 As the size of the pond increases, the size of the waves increases and erosion becomes
stronger;
9 As the slope ratio increases, the volume of earthwork increases, and the overall land area
required for the ponds increases
Usually side slopes of dikes vary from 1.5:1 à 3:1, which 18° to 45° (Figure 68 and Table XVI
above), depending on local conditions for ponds of 100 to 600 m2. The slope of the dry side can be
made steeper than the slope of the wet side.
The care taken to the construction of the dikes is an essential component of the lifespan of the
ponds (Figure 69, Figure 70 and Figure 71, p. 88 and Photo F, p. 89).
To build the dikes, one digs the ground of the major part of the pond: one removes the too sandy
ground (A). The good argillaceous soil is transported and compacted wet, by a compactor or while
rolling a barrel of 200 l filled with water on the site of the dikes.
Each layer of good 10 cm thickness wet argillaceous soil (not containing vegetable nor large
stones) is vigorously rammed (B). If one rams a layer of too thick soil, the ground will not be well pac-
ked in-depth. The ground will be well compacted and dikes well seals if the dikes are built according
to this technique called “in staircase”. One uses a compactor, a barrel, or a roller for compacting
each stair well, one after the other. The majority of the water escapes are due to a bad compaction,
in particular above the outlet. Each stair, of decreasing width from the bottom to the top, is rammed
and compacted vigorously (C). After having assembled the dike, step by step, until the height of
desired water (0.6 to 1.2 m) according to the type of pond (laying, stocking with fish, parent) and
without forgetting the height of the freeboard of 0.25 m, it is enough to flatten the edges of the steps
with a wooden handle.
In the very argillaceous soils, the soil is more difficult to work and some prefer to build the dikes
with blocks of ground which they cut in the ground. The sandy grounds are easier to work and are
crumbled in the hands: they are very permeable and are less appropriate for fishfarm (D). To build
dikes on clay soils, one proceeds in the same way, (method of the staircase) but one moves the
ground by cut mound, removed the vegetable top layer and the large vegetable debris (E). With a
little water, each argillaceous lump of earth is sticks to neighboring clumps and form a solid and im-
permeable paste, which strongly adheres to the clay soil on which the dike is built. One often forgets


A B C

D E F
Figure 69. Construction of the dikes (I). A, B and C: Traditionnal; D, E and F: By blocks.
Water supply channel Water supply channel

Drain channel Drain channel

Figure 70. Construction the dikes (II). Figure 71. Preparation of the bottom.
to clean the lumps thus causing useless water escapes through the dikes. After having deposited
side by side the lumps of earth all along the dike to be built, one sprinkles and one crushes each
stair over all his length so that each argillaceous lump of earth is stick to its neighbors (F). Moreover,
one will use a roller or a barrel of 200 liters filled with water or a compactor for compacting the dike
well over all his length.
If the dikes of the pond are well built with adapted soil, the pond will be able to last more than
twenty years with little maintenance.
Either during construction, one leaves space for the structures of inlet and outlet, or those are
made at the same time. One will see later on how to build them.
Once the dikes are built, one will be able to deal with the plate or bottom of the pond.


3. PONDS

Photo F. Dikes. On left: Slope badly made, destroed by erosion (DRC)[© Y. Fermon];
On right: Construction (Ivory Coast) [© APDRA-F](CIRAD).

VII. THE DEVELOPMENT OF THE PLATE (BOTTOM)
The pond having to be completely empty without remaining water puddle pools there, one ar-
ranges the bottom or the plate in soft slope towards the outlet (Figure 72 below).
The construction of the bottom of the plate is done by clearing the bumps to remain slightly in
top of the projected dimensions. For the embankments, a particular care is given here to the com-
paction and the choice of the quality of the soil to be used, because one is in a case similar to that
of the supply channel which is permanently submerged.
In the case of small ponds, the bottom must be with a soft slope (0.5 to 1.0%), since the water
inlet to the outlet, to ensure an easy and complete dry setting of the pond. One must always make
sure that the entry of the outlet is slightly below the lowest point of the bottom of the pond.
For the ponds whose surface is rather important (more than 4 ares) the installation of ditches of
drainage towards the emptying device is very useful. It is preferable to ensure a complete dry setting
by a network of not very deep ditches of draining and having a slope of 0,2 %, rather than to seek to
create a slope on all the plate of the pond.
When the bottom of the plate is entirely regularized, one will carry out the digging of the drains
converging of the edges towards the zone of draining. The drains are small channels built to facilitate

I = Inlet I
I
O = Outlet

I

O
A B O C O
Figure 72. The bottom or plate. Direction of the slope (A)
and drain setting: In ray (B); As «fish bones» (C).


the total evacuation of water. All the various operations are carried out by respecting the data of the
plan and the level stakes. One can lay out the drains (Figure 72, p. 89):
9 In ray starting from the outlet, or
9 In “fish-bones”.
The ditches of draining must be all connected to a harvesting pit dug in the deepest part of the
pond, usually in front of the outlet, where all the fish can be gathered for harvest (Figure 73 below).
It is necessary not to forget to include the following differences in level (Figure 74 below):
9 Between the end of the ditch of draining and the bottom of the harvesting pit (at least 20 cm).
9 Between the bottom of the harvesting pit and the bottom of the outlet (at least 10 cm).

VIII. THE CONSTRUCTION OF THE POND INLET AND OUTLET
It is a question, here, of seeing which are the inlet and outlet of the water of the ponds, i.e. how
to get water in the ponds and how to empty them completely, while managing these inflows and
outflows of water.

VIII.1. POND INLET STRUCTURES
Inlet structures are built to control the amount of water flowing into the pond at all times. There
are three main types of inlet structures:
9 Pipe inlets,
9 Open gutter inlets,
9 Canal inlets.
When designing and constructing an inlet structure, one should pay particular attention to the
following points: (Figure 75, p. 91):
Ö The inlet have to be placed at the shallow end
of the pond.
Harvesting pit Ö The bottom level has to be at the same level
Monk
as the bottom of the water supply channel and
ideally at least 10 cm above the maximum level
of the water in the pond.
Ö The inlet structure have to be horizontal, with
a minimum to no slope.
Ö The structure have to be arranged so that
Fish-bone water splashes and mixes as much as possible
pattern when entering the pond.
Ö The structure have to be made to avoid the
Figure 73. Bottom drain. entry in the undesirable aquatic animal or fish in
the pond.

Crest of
Normal water dike
Monk with
level
screen in place

Pond bottom Harvesting pit
(pente 0.5 %) Drainage
(± no slope)
channel

20 cm
10 cm
Bottom drain Sloping outlet
(slope 0.2 %) pipe

Figure 74. Cross cut of a pond at the bottom drain.


3. PONDS
Bottom of the water Inlet Bottom of inlet 10 cm above
supply channel maximum water level
Shallow end of
the pond

Bottom of the inlet at the
same level as bottom of
the water supply channel

Figure 75. Cross cut of the inlet of a pond.

VIII.1.1. PIPE INLETS
Pipe inlets can be made from various ma-
terials, depending on the water supply required
and the inside diameter of the pipe (Figure 76
opposite). Usually, pipe inlets extend for about
60 to 100 cm beyond the edge of the water sur-
face of the pond when it is full, and they should
be at least 10 cm above the final water level.
One will mainly use PVC pipe or plastic, which
are resistant and do not deteriorate easily. In the
cases where they are not available, bamboo can Figure 76. Pipe inlet.
be used.
Bamboo pipesmake cheap and good inlets
whenever locally available (Figure 77 opposite).
They can be used in several ways for filling small
ponds, for example:
9 Without modification, the water flow
Oblique
being regulated upstream; Flow
cut
9 With the inclusion of a mobile plate for
flow regulation; Metal plate to
open and
9 With modification for improving water close pipe
quality.
Flow
VIII.1.2. GUTER INLETS
Gutter inlets usually extend for about 1 m
over the water surface when the pond is full (Fi-
gure 78, p. 92). They can be made simply from va-
rious materials such as (Figure 79, p. 92):
Pipe blocked
9 Bamboo: by cutting a bamboo culm at end
lengthwise in half and cleaning out the partition
walls. The diameter is usually limited to 10 cm Figure 77. End of bamboo pipe.
or less;
9 Wood: by assembling three boards to form a rectangular gutter. A flow-regulating gate can
easily be added;
9 Metal: by bending lengthwise a galvanized iron sheet into a semi-circular gutter. The flow
should be regulated upstream.


Split bamboo gutter

Wooden gutter

Board water
control
Figure 78. Gutter inlet.
About
1m Corrugated
metal gutter

Corrugated
metal gutter

Figure 79. Different types of gutter.

VIII.1.3. CANAL INLETS
A small open canal can be built to connect
the water supply channel to the pond (Figure 80
opposite). There are several possibilities such as:
9 Digging a small earthen canal, with a tra-
pezoidal section;
9 Building a small lined canal, with a rec-
tangular section and using either wood, bricks or
concrete blocks. Small parallel walls are built on
a light foundation along the sides of the canal. Figure 80. Canal inlet.
If necessary, two pairs of grooves are added to
regulate the water flow with thin boards and to
keep unwanted fish out with a sliding screen.
VIII.1.4. SOME ADDITIONAL POINTS
■ THE OxYGENATION OF WATER
One can rather simply increase oxygen in water at the inlet of a pond when water falls in the
pond. The principle is to increase the surface of contact between the air and water. The mixture of
atmospheric oxygen to water improves as:
9 The drop height of water increases,
9 The width of the water and the surface of contact with the air increases,
9 The lapping and the fragmentation of water in fine droplets increase.
If water feeds the pond through a pipe, one can improve oxygenation:
9 By adding an elbow of 90º at the end of the pipe, opening upwards;
9 While placing a vertical filter perforated on the reversed end of the pipe;
9 By fixing a horizontal perforated screen so that it curves around the end of the pipe and
exceeds it slightly.
If the feed water falls vertically in the pond via a device in overhang, one will be able to improve
oxygenation by putting under the jet a horizontal, plane or undulated panel, which will break the jet.
■ THE LIMITATION OF THE EROSION OF THE POND
It is essential to position under the water arrival, blocks of stones which will avoid growing hollow
in this place of the pond.


3. PONDS
VIII.1.5. THE FILTRATION
At the inlet, filtering devices of water are usually used:
9 To improve water quality by reducing turbidity and while allowing to eliminate certain organic
matters in suspension, such as vegetable debris.
9 To limit the wild fish introduction, which can take food, transmit infections and diseases and
reduce the production of the ponds. The carnivorous species can destroy the fish stock, in particular
smaller ones.
It is possible to make various types of more or less effective structures and more or less heavy
to implement. Initially, one can put a rather coarse stopping like a grid, on the level of the general
water supply channel or the pond to prevent the large debris to pass into the ponds. For the aquatic
animals, one will use finer structures. Often, simple net, sometimes mosquito net, were used on
the inlet (Photo G below). However, either these grids are filled very quickly and thus require a daily
cleaning, or they are destroyed because not solid
enough. One can indeed set up more elaborate
structures, but which often require higher over-
costs. However, it is possible to set up a system
simple, not too expensive and requiring a regular
but nonconstraining maintenance, may be only
one to twice a year, if water is rather clear. It is
a question of making pass the water by gravels,
then by sand filter (Figure 81 and Photo H, p. 93).
If the feed water is too turbide and char-
ged in sediment, it is possible to set up a filter
Photo G. Example of non efficient screen at decantation before its arrival in the pond,. The
the inlet of a pond (Liberia) [© Y. Fermon]. principle is simple. It is enough to install a small

Photo H. Example of filters set at the inlet of a pond in Liberia [© Y. Fermon].
To fill with Filtering mass
the filtering masses Gravel Sand
Wire netting

Debris

Concrete Water supply
channel
Water
Pond
Wild fishes

Dikes

Figure 81. Diagram of an example of sand filter.


basin upstream and to make water pass there to low flow. The particles will settle to the bottom of
the basin which will have to be emptied with saturation. The water which will arrive at the pond will
be then clear. This will be later on explained.

VIII.2. POND OUTLET STRUCTURES
A fishpond of built well must be able to be emptied completely through an outlet device adapted
to the dimensions of the pond.
Before starting the construction of the dikes themselves, it is necessary to envisage the instal-
lation of an outlet device. Preferably, one will install the system of draining at the same time as the
construction of the dikes, by leaving the necessary space, or before the dikes.
Two main reasons justify the construction of outlet structures:
Ö To keep the water surface in the pond at its optimum level, which usually coincides with the
maximum water level designed for the pond;
Ö To allow for the complete draining of the pond and harvesting of the fish whenever necessary.
In addition to these major functions, a good outlet should also ensure as far as possible that:
Ö The amount of time necessary to drain the pond completely is reasonable;
Ö The flow of the draining water is as uniform as possible to avoid disturbing the fish excessively;
Ö There is no loss of fish, especially during the draining period;
Ö Water can be drained from the top, bottom or intermediate levels of the pond;
Ö Any reasonable excess of water is carried away;
Ö The outlet can be easily cleaned and serviced;
Ö The construction cost and maintenance are relatively low.
In most cases, outlets have three main elements:
9 A collecting area on the inside of the pond, from which the water drains and into which the
stock is collected for harvest;
9 The water control itself, including any drain plugs, valves, control boards, screens and
gates;
9 A means for getting the water to the outside of the pond such as a pipe or a cut through
the wall, and/or an overflow structure. In both cases, a protected area on the outside of the wall must
prevent the drain water from scouring the walls or drainage channel.
Pond outlets can be built in various ways, using different materials such as bamboo, wood,
bricks, cement blocks or concrete. There are four main types:
9 Simple cuts through the dike;
9 Simple pipelines and siphons;
9 Sluices dikes;
9 Monks.
In several handbooks, one recommends that a simple pipe is enough: it can be in bamboo, PVC,
wood, iron or concrete and of a diameter of at least 100 mm for the small ponds from 3 to 5 ares. The
interior diameter of draining will determine the capacity of flow of the structure. However, in practice,
it appears that above 100 m2 (or 1 are), the monk is most reliable and allows a good management
of the water of the ponds. For the lower ponds (storage, stocking with fish), one will be able to use
pipes. So only the two preferential methods of draining will be shown here.
VIII.2.1. PIPE OUTLETS
One will choose the size and the quality of the pipes which it is advisable to use according to the
surface of the pond and the necessary diameters. Diameters from 5 to 10 cm is enough for ponds
to size lower than 100 m2. The pipes can be in bamboo, galvanized metal or plastic (PVC). An outlet
can be a straight of low diameter. It is important that the pipes used for this purpose are installed at
the lowest point of the pond, before the dike is not built. The method with a pipe which is the best to
control the height of water is that to use a turn-down stand-pipe.


3. PONDS
This pond outlet is made of three rigid plastic parts:
9 A slightly sloping base pipeline, made for example of one or more PVC pipes running through
the dike,
9 A vertical pipe, which reaches up to the maximum water level;
9A 90°-elbow, which connects these two
pipes. It can be glued to the vertical pipe with
plastic cement, but need not be unless the fit is
Steel post very loose. The connection to the base pipe is
Pipe with screen at unglued, but can be greased with a suitable ma-
water level terial such as mineral grease, lard or palm soap.
This type of outlet can be set up either in-
side the pond, in front of the dike or outside the
pond, at the back of the dike, in which case you
need a screen at the inner end of the base pipe.
It is usually best to have the vertical pipe inside
the pond to reduce the risk of blocking the ho-
Attach pipe to rizontal pipe and to control leakage (Figure 82
steel post below).
If possible, design the opening of the ho-
Wooden rizontal pipe to be at least 10 cm below the
board lowest point in the pond. One can carefully fix
the vertical pipe at the steel stake located in
front with a rope or a chain, which avoid acci-
dental movements. One will place at the end of
10 cm the vertical pipe a narrowly adjusted netting.
Concrete anchor will To regulate the water level in the pond, it is
hold pipe firm just enough to set the pipe at the required angle
by turning it up or down. Then, one have just to
90° elbow fix it in the set position with the chain or rope.
Unglued

Maximum water level Maximum water level

Partially empty
Completely
Lower pipe to empty
empty pond

Water level
Drainage of the water
Protection
of the pipe Downstream dike Downstream dike

Drain pipe Drain pipe

Figure 82. Turn-down pipe inside pond outlet.


To drain the pond, one will turn the vertical pipe down progressively, following the water level as
it drops. When it has reached the horizontal position, one will just remove the elbow pipe from the
end of the horizontal pipe to end the draining of the pond and harvest the fish.
It is possible to use this system for handling normal overflow water, because any surplus in the
pond above the selected pipe level will automatically drain.

VIII.2.2. THE MONK OUTLET
The monk is one of the oldest and most common pond draining structures.
The monk is a U-shaped pipe towards the interior of the pond, and prolonged at his base by a
drain. Water is evacuated by this drain under the dike. The structure is built at the deepest point of
the pond. The monk includes two side and a back. Two or three parallel grooves arranged vertically
on each side can receive small boards of wood which, by juxtaposing each other, closes the monk
on the open side towards the interior of the pond. Space between the first two lines of small boards
is stuffed with clay, to make this part watertight. In the third possible pair of grooves, grids replaced
small board and prevent the escape of fish during drainings. This third pair of grooves is very useful
in practice especially at the end of the draining. Indeed, when one reaches the last water fringe at the
bottom of the pond, the capture of fish accumulated in front of the opening of the monk always does
not leave time as well as possible to manage the first two pairs of small boards, and the presence of
the grids in the third consequently appears salutary.
The pond water level is easily controlled and adjusted. It can function as an overflow. It simplifies
the fish harvest. In addition, a monk is more easily to use, and it is more economical to build if the
pond dike is large. However, it has the disadvantage of not being very simple to construct, particu-
larly if it is built with bricks or concrete.
The complete monk outlet consists of (Figure 83 below):
9 A vertical three-sided tower (called the monk), usually as high as the outlet dike;
9 A pipeline running through the dike, which is sealed to the back of the tower at its base;
9 A foundation for the tower and the pipeline; and
9 Grooves to fix the wooden boards and screens which form the fourth side of the monk.
Similar to any other outlet, the monk is generally built on the side of the pond opposite the water
inlet. It may be placed either in the middle of the dike or, when the water drains, for example, in a
catch basin common to two adjacent ponds, in a corner of the dike (Figure 84, p. 97).
The foundation of the monk is built by taking account of the later pressure of water on the
structure, and especially of the levels to respect to ensure the gravitating draining of the pond. In
any case, the base of the monk in front of the draining pipe will have to be slightly in lower part of
the lowest point of the plate of the pond, and of course, higher than the maximum level of the bed
of the river of drainage.

Wire netting Clay
Grooves Pipeline
Drainage of the water

Wooden plates

Verticale
tower

Foundation

Figure 83. Composition of a monk.


3. PONDS
The monk can be built either into the
Water supply channel dike or freestanding some distance into
the pond (Figure 85 below):
Ö If the monk is built into the dike, water
infiltration through the dike will be more
common and access to the outlet will be
easier for poachers. To prevent soil from
Monk in Monk in a
entering the monk, you will have to build
the middle corner
an additional protective wing on both
sides, but servicing the monk will be ea-
sier;
Ö If the monk is built on the pond bottom
in front of the inside toe of the dike, you
Drainage channel will need a longer pipeline, but access to
the monk will be through a removable ca-
Figure 84. Position of the monk in the pond.
twalk and tampering with it will be much
more difficult.

Monks can be built in wood, bricks or concrete depending mainly on the availability of materials,
their cost, the local technical expertise and the size of the structure.
The most difficult type of monk to build is the brick monk. It requires a very skilled mason to
make it so that it is leak-proof. If not done properly, the mortar surfacing will have to be redone
frequently, increasing maintenance costs. Generally, wooden and concrete monks are cheaper and
easier to build. The following are some points to remember when one build a monk:
Ö The pipeline should be laid down before building the dike and the monk tower.
Ö A solid foundation have to be built to avoid future problems.
Ö A particular attention have to be paid to the junction of the monk tower to its foundation; the
junction of the pipeline to the back of the monk tower; the finishing of the monk’s grooves.
Ö A reasonable slope to the pipeline have to be made, preferably 1.5 to 2 percent.
Ö If several monks have to be build on the fish farm, one have to try to standardize their type and
size as much as possible; and, for concrete monks, one need to prepare strong forms and re-use
them if possible.
Ö One have to provide a separate overflow wherever there is danger of uncontrolled entry of flood
water into the pond.

Top of the Top of the
dike dike
Monk Monk
Outlet Outlet
Dike Dike

A B

Figure 85. Position of the monk according the downstream dike. A: Integrated in the dike;
B: Inside the pond.


■ WOODEN MONK OUTLETS
A simple monk outlet can be built entirely of wood. It is the easiest and cheapest type of monk to
construct, although you need to be careful to ensure its watertightness and its durability. The height
of a wooden monk should be limited to 2 m (Figure 86 below).

3 x 5 cm
cross-support

5 x 5 cm posts 5 x 5 cm posts

Inside Inside
dimensions dimensions
≈ 20 x 22 cm ≈ 28 x 46 cm
100 à 120 cm

150 cm

Oblique
brace
Pipeline
Pipeline

27 cm 50 cm 50 cm
30 cm
A B
Figure 86. Wooden monk. Small (A) and medium (B) size.


3. PONDS
To build a monk out of wooden, it is necessa-
ry to choose a heavy and durable wood, resistant
to water. The durability of wood can be improved
by application of a discarded engine oil or pre-
servative. One should not however forget to wash
wood before putting the fish in the pond.
It is necessary to use small planks without
knots, from 3 to 5 cm thickness. Thus, one will
need approximately 0.4 m3 of wood for a 2 m
height monk.
In the majority of the cases, it is not necessary
to envisage foundations as they are very light, al-
Figure 87. Wooden pipe. though in the presence of less stable grounds it
can be indicated to envisage simple piles of woo-
den for foundation. Usually, it is sufficient to build them on light foundations, for example flagstones
of paving or simple wood piles or rather broad boards posed flat on the bottom of the pond.
Both the small- and the medium-size monks are composed of boards nailed or screwed to-
gether, so that the face turned towards the pond is open. It is preferable to screw a post of anchoring
on each side of the column. It is necessary first of all to insert these two posts until a sufficient depth
in the bottom of the pond, then to screw them with the monk.
If one wants to improve solidity of the work, it is possible to add an oblique brace to each side,
supporting the upper part of the column against the drain.
Instead of using standard elements of concrete or plastic drain, one can entirely build a drain
in wood (Figure 87 above). It is enough for this purpose assembling by nails or screws four boards
assembled out of rectangular box. One carefully fixes the drain thus carried out on a well compacted
soil and one hides it under the dike.

■ SMALL BRICK, CONCRETE BLOCK AND CONCRETE MONK OUTLETS
Monks of up to 1.5 m in height, fixed to pipelines up to 25 to 30 cm in diameter, can be built
using single- thickness brick and mortar. Although taller and wider monks can be built, they require
a double-width base and good bracing for stability and strength, and so become too heavy and
expensive for most purposes.
The rules of construction to be observed for small monks are:
Ö The monks in bricks and breeze blocks must have interior surfaces carefully finished, covered of
a coating. This technique revealed three major problems:
1. The breeze blocks are hollow and rough-casting is exhausted quickly. Escapes, not easily
reparable, appear on the growing old monks.
2. The monk is often unnecessarily tall within sight of the flow which the pipe can evacuate (what
requires of the rather long and relatively expensive boards to close the monk).
3. It is impossible to carry out two of the same width monks being able to use the same grids or
the same boards.
On the other hand, this construction is not expensive.
Ö For concrete structures, it is necessary to request the services of a qualified mason. The quality
of execution must indeed be excellent to guarantee the durability of the work.
At the beginning, the construction of the formwork was done on site. Construction on site of for-
mwork made it possible to make the concrete which took the shape of a monk to the release from the
mould. This technique presented a difficulty at the time of its implementation. The construction of the
mould on the spot proved to be delicate, the sometimes hazardous dismantling and the problematic
recovery of the boards. What increased much the cost of construction. The monks were generally of
different sizes but much more solid.
Since one uses a better solution: the dismountable and reusable mould (Figure 88 and Photo I,
p. 100). The idea was to design a reusable dismountable mould. Moreover, this solution guarantees a
standard dimensioning. However, the first moulds were rather heavy to transport. When the fishfar-


Clamp

A B
Figure 88. Mould of a monk. A: Front view; B: Upper view.

mer invested itself in the research of sand and the gravel, these monks were finally less expensive
than those which are carried out in breeze blocks. Then, this type of formwork undergoes major
changes. As private individuals again, the mould is from now transportable by only one person with
foot or bicycle. The shuttering timber coats oil internally (engines oil of vehicles for example) is thus
carried out above the foundation in order to run the wings and the back of the monk.
As an indication, the dimensions presented in Table XVII below can be adopted, according to the
size of the pond. Thus, for a pond from 0.5 to 2 ha, the formwork to be run will be able to have: 2 m

Table XVII. Informations on the dimensions of the
monk according the size of the pond.

Surface of the
S < 0.5 ha S > 0.5 ha
pond
Height (m) 1.50 2.0,
Bach width (mi) 0.54 0.70
Sides width (m) 0.44 0.54
Depth of concrete 0.12 0.15

Photo I. Mould and monks (Guinea). On left: The first floor and the mould;
On right: Setting of the secund floor [© APDRA-F] (CIRAD).


3. PONDS
Table XVIII. Estimation of the discharge and draining duration of the pond
according the diameter of the outlet.
Time for the drain of a pond of 4 ares
Diameter (cm) Discharge (l/s-1) Discharge (m3/h-1)
(Mean depth: 1 m)
10 8 28.8 13 h 53
15 18 64.8 6 h 11
20 31 111.6 3 h 35
30 70 252 1 h 35
40 130 468 52 mn

from height, 0.7 m of width of the back, 0.54 m for the wings and 0.15 thickness. The mixture of the
concrete to be used will be of 1 volume of cement for 2 volumes of fine sand and 4 volumes of gravel,
for the monk described, 4 cement bags, 4 sand wheelbarrows and 8 crushed stone wheelbarrows.
The capacity of flow of a monk is related to the internal diameter of the drain. The cross section
of the monk increases according to the diameter of the drain (Table XVIII above, Table XIX and Figure
89 below).
The following points are important:
Ö The interior width of the column must be equal to the diameter of the drain increased from 5 to
10 cm on each side;
Ö There must be a space from at least 8 to 10 cm in front of the first groove;
Ö The two series of small boards must be separated by an interval from at least 8 to 10 cm;
Ö The distance between the last series of small boards and the back face of the column must be
all the more large as the capacity of flow is high, without however exceeding a maximum value from
35 to 40 cm
To facilitate the operation of the small boards, it is preferable to limit the interior width of a monk
to a maximum value of 50 cm.

D Table XIX. Inside dimensions of the monk according the
diameter of the pipe.
5 to 10 cm 5 to 10 cm
Pipeline inside diameter (cm)

3 10-15 15-20 20-25 25-30

L r Internal width 30 33-35 40 48-50
2
r In front of groove 1 8 10 10 10
1
Gap between grooves
8 10 10 10
W 1 and 2
W = Width Distance between
D = Diametre of the pipe 16 16-20 26 34-37
groove 2 to wall
L = Lenght
r = Grooves Width for two grooves 8 8 8 8
W = D + 2x (5 to 10 cm)
L = (1) + (2) + (3) + r + r Internal length 40 44-48 54 62-65
(1) = 8 to 10 cm
(2) = 8 to 10 cm
(3) = maximum 35 to 40 cm Figure 89. Monk. Upper view
r = 4 cm each and example of size.


Photo J. First floor of the monk associated
with the pipe (Guinea) [© APDRA-F](CIRAD).

Clay

Photo K. Top of a monk (DRC)
[© Y. Fermon].

The maintenance of the mould requires a
minimum of attention. It is preferable to store it
made so that it becomes not deformed and to
coat it as soon as possible with engine oil. Used
well, a mould can make more than 20 monks.
By leaving some iron stems in the still fresh
concrete to make the junction with the following
stage, it was completely possible to build by
stage a monk of more than 2 m (Photo I, p. 100 and
Photo J above).
The soil used between the small planks to
block the monk must be rich in organic matter in
order to keep its plasticity. Too pure clays often
fissure side of the tube, which is not long in cau-
sing escapes.
The height of water in the pond is thus regu-
lated by the monk thanks to the small boards out
of wooden between which one packs clay (Figure
90 opposite). Water is retained in the pond by this
impermeable layer up to the level of the highest
small board.
Netting at the top of the last small board pre-
Figure 90. Functioning of a monk. vents fish from leaving the pond over the highest


3. PONDS
Build wooden
form using Top cover
2 cm boards
Chip a notch in the foundation
to secure side walls

A
Foundation

B C

Figure 91. Concrete pipe. A: Croos cut; Photo L. Building of a pipe
B: Mould; C: Final pipe. (Guinea) [© APDRA-F](CIRAD).

small board of the monk. One will always take care that the meshs of netting are smaller than fish
raised in the pond.
When the pond is filled to the last small board, all the water which enters more in the pond,
crosses the grid above the impermeable layer and falls to the bottom of the monk. In this place, it
crosses the dike then leaves the pond while passing by the drain (Photo K, p. 102).
The monk ended, it is essential to equip it with foundations called soles. The sole is also used as
plane surface and hard to catch last fish easily.
The monks of this type are generally provided with drains. One can use a PVC drain or set up
concrete tubes. If one wants to obtain the best results, the drain must have a good foundation whose
construction must be done at the same time as that of the column of the monk (Figure 91 and Photo
L above). The seals of the drains must be carefully sealed to avoid the water escapes.
In the wet environments, because of water abundance which compensates the risks of escape,
the concrete tubes constitute a good technique:
Ö They are cheap: two baggs of cements are enough for 10 m of tube for which it is necessary to
add a half bagg for the seals;
Ö Their section allows an higher capacity that of a pipe of 100 or 120 mms in diameter;
Ö The flat bottom of the tube makes it possible to accelerate the ends of draining, which is very
practical;
Ö It is easy to add a tube when the need is felt some.
However the concrete tubes present also some disadvantages, in particular in the dry zones,
which are as many recommendations:
Ö The mould must be quite manufactured and correctly maintained so that the junctions are en-
casable and remain it;
Ö It is preferable to assemble the tubes before building the dike, it is thus easier to move the water.
One can then install them on a dry and hard soil instead of posing them on mud;


Ö It should be taken care that the tubes are well buried under the slope so that when the fishfarmer
goes down to this place to visit his monk, it does not loosen the covers of the tubes;
Ö Along the tubes (as along the pipes) a zone of weakness constitutes around which it is carefully
necessary to ram, if not risks of infiltrations is important.
VIII.2.3. ADDITIONNAL STRUCTURE OF OVERFLOW
For safety reasons, one will have to always prevent that the water level in the pond exceeds the
maximum level and that water flows over an unspecified dike. Any water in excess which penetrates
in a pond already filled - water of flood or of streaming, for example - must be immediately and au-
tomatically evacuated. Such an incident would cause the loss of most of the fish stock and would
require also important repairs before starting again the exploitation of the pond.
In the case of a diversion pond, of which most of overfow is diverted at the diversion structure, a
draining device such as an open vertical pipe or a monk must evacuate any overflow automatically.
It should however be taken care that all the grids are maintained in good state of cleanliness. A monk
also provides the function of overflow. One can however add an additional pipe to mitigate the filling
of the grid for lack of attention.
During heavy rains, the amount of surface runoff may become excessive, particularly for barrage
ponds or ponds built at the bottom of large sloping areas with little vegetation cover. The runoff water
in such cases is also often heavily loaded with fine soil particles that make it very turbid. If the runoff
passes across cultivated areas it might accumulate toxic substances such as pesticides. To avoid
such water reaching your fish farm, you will have to protect it with one or more protection canals
If the pond is deprived of emptying device to free flow or if this device is too small, and if the
quantity of water in excess is always limited, it is possible to install a pipe of overflow which can be
in bamboo, PVC or galvanized iron (Figure 92 below). It is best to use one-piece pipes, avoiding any
joints. If the pipe sags, or extends too far out from the outer side of the dike, it may be useful to put
up some simple pipe supports, using for example wood or bamboo.

Protecting Protecting outside of Supporting a
outside of dike dike with a long pipe
with stones corrugated metal
channel

Maximum water level

Angle the pipe so that
inside opening is 15
to 20 cm below
maximum water level

Place overfow at Maximum water level
corner of pond

Remove deeper water
by curving down inside
Figure 92. Setting of a pipe end of pipe
overflow.


3. PONDS
VIII.3. SEDIMENTATION TANK
A sedimentation tank (or setting basin) is specifically designed to improve water quality by re-
moving the mineral soil particles, such as fine sand and silt, which can be present in great quantities
in certain waters with a high turbidity. This is achieved by reducing the water velocity sufficiently to
allow the particles to settle.
There are different types of settling basins (Figure 93 below):
9 A simple small pond, built at the beginning of the water supply channel;
9 A rectangular basin built on the feeder canal with bricks, cement blocks or concrete (Figure
94, p. 106).
If the settling basin is a simple rectangular basin, the size will be determine as follows:
¾ Its minimum horizontal area. For example, for a flow of 0.030 m3.s-1 and to settle a particle
which has a diameter greater than or equal 0.1 mm, Therefore the minimum horizontal area of the
settling basin will be of 5.6 m2. in these ideal conditions, 100 % of particles of 0.1 mm or larger
should settle. A smaller proportion of smaller particles will also settle. The smaller the particles,
the less the percentage settling.
¾ The minimum cross-section area . It will be of 0.3 m2, in the following example.
¾ The minimum width. In the following example, it will be of 1.2 m.
¾ The standard length. It will be of 4.6 m in the example.
¾ The depth, which is the sum of the water depth (0.25 m), the freeboard (0.20 m) and the setting
depth (from 0.10 to 0.20 m). In the example, it should be of 0.60 m.
The settling basin can be wider, with a larger cross-section. This will then allow the standard
length to be shorter. As long as the critical velocities are not exceeded, the basin can be shaped
to fit local space and to minimize construction costs. As a general guide, ratios of length: width are
typically between 2:1 and 5:1.
The bottom of the settling basin is built lower than the bottom of the water feeder canal, to
concentrate the soil particles being removed from the incoming water.
The above design can be improved in the following ways:
Ö At the entrance, make the water pass over a wide edge near the basin’s surface, similar to a weir,
to minimize disturbances.
Ö At the exit, similarly make the water spread over a wide edge near the basin’s surface.
Ö Avoid cross-wind exposure as this can often agitate the water and resuspend particles.
Ö Within the basin, add some baffles to slow down the water further and make it follow a longer
zig-zag path. With these baffles, you can reduce the basin’s length by one third.

3 m - 10 m 1 m x 7 m

Sand and
Sand and silt
silt

A B

Figure 93. Type of setting basin. A: Natural; B: In concrete.


0 1 m 0 1 m
Section Section
A B
2 %
Figure 94. Setting basin.
A: Normal; B: Improved. Plan

Ö Make sure water flows evenly and quietly through the settling basin. Avoid creating areas of
turbulence or rapid flow.
Ö Provide a sloping bottom (slope = 2 percent) from the downstream end to the entrance of the
basin.
The settling basin have to be regularly clean by removing the accumulated soil from its bottom
after closing the water supply. This soil have to be removed more regularly using a simple pipe or
siphon. Usually, the soil is very fertile, and can be use it in the garden and fields to make the crops
grow better.

Ix. ADDITIONAL INSTALLATIONS
Ix.1. THE ANTI-EROSIVE PROTECTION
Once the pond dug and the various works in place, the dikes must be protected from erosion,
by sowing grasses crawling on the upper part, at the top, on the dry side and the wet side up to the
normal level of water (freeboard) in the pond.
For that, one can spread out a layer from 10 to 15 cm of topsoil over the zone to be turfed (Figure
95 below). This ground is obtained either from the topsoil stock previously extracted with the site
pond, or in the vicinity. One will plant the cuttings or the turfs with relatively brought closer intervals.
Then, one will sprinkle immediately after having planted and, thereafter, with regular intervals. As
soon as the grass is established, it should be cut short regularly to stimulate its extension to all
surface.
In the event of strong rains, one can use a temporary protective system, for example hay or other
materials, as a long time as herbaceous cover is not complete.
One can use the space of the dikes (Figure 96, p. 107). In certain areas, pot cultures or fodder
plants can grow (A) there, but it is necessary to take care to choose species ensuring a good cover
of the ground and of which the roots are not likely to weaken the dikes too deeply by penetrating
the ground or by altering its structure. Only of small animals can graze or circulate above (B). One
should not plant trees on the surface or near the dikes, because the roots would weaken them (C).

10 to 15 cm of steppe
black soil Plant grass Seed

Figure 95. Setting of a vegetable cover on the dikes.


3. PONDS

A B C
Figure 96. Dikes with plants. A: Vegetable garden; B: Small animals;
C: Trees.

Ix.2. THE ANTI-EROSIVE FIGHT
At the time of the installation of the ponds, it is particularly important to make sure of the risks
of erosion of the catchment area. The erosion of the ground has negative effects on water quality
and on the fishfarming installation itself. When water runs out on a slope, it involves with it particles
coming from the ground of surface. More the flow is important and fast, more there are carried par-
ticles. Erosion can involve:
Ö Serious degradations of the slope itself and properties of the ground, which reduces the fertility;
Ö An arrival of turbide water in bottom of the slope and problems of deposits of ground elsewhere.
It will be necessary to try to control as much as possible the erosion of the grounds on the
slopes to prevent that turbide water does not go in the ponds (Figure 97 below). This practice, called
conservation of the grounds, can generate significant advantages:
Ö Richer soil on the slopes and a greater production of various products such as wood, fruits,
fodder or food;
Ö A better water quality in the ponds and a more important production of fish.
The vegetation protects the ground against erosion. The roots contribute to stabilize the particles
of ground and to increase the permeability of the sub-bases. The organic matters which it brings in
the ground, like the humus, increase resistance to erosion and slow down the streaming. It can also
contribute to the deposit of the particles of ground.
By arranging the natural vegetation on the slope grounds, it is possible to guarantee that the
ground acquires a greater resistance to erosion. In the zones covered with forests, it is necessary to
completely maintain the cover of the ground as possible by managing the exploitation of the trees
and by protecting the forest against the excessive pasture and fires. The forests having a good
low vegetation, well disseminated radicular systems and a good cover by the leaves offer the best
conditions. In the zones of savanna, one will control the use of fire for the regeneration of the grazing
grounds and will give the preference to early fires to guarantee sufficient new growths before the
beginning of the rains. It will be necessary to avoid the excessive pasture, in particular by the sheep
and the goats. As soon as possible, it is necessary to envisage rotations for the pastures.
If one is not able to fight against erosion, one can have recourse to a channel of protection to
collect and divert water turbides or, if necessary, to improve water quality of food by using a setting
basin (paragraphe VIII.3, p. 105).

Pond g Pond Pond
Streamin
A B Infiltration C Protection channel

Figure 97. Type of erosion and soil conservation. A: Streaming; B: Infiltration;
C: Protection channel.


Ix.3. BIOLOGICAL PLASTIC
If the ground used can let infiltrate water, it will be necessary to use the technique of “biological
plastic”, to reinforce the sealing of the plate of the pond. This technique allows to reduce the water
leaks and infiltrations by filling the plate and the dikes of a pond built on a ground not impermeable
enough. The realization of the biological plastic is done in the following way:
1. After having regularized the structures well by removing vegetable debris and stones, one
covers all the plate and the future water side of the dikes with waste of pigsty.
2. One recovers then this waste using leaves of banana tree, straw or other vegetable matters.
3. Then, one spreads out a layer of ground over the unit and one rams copiously.
4. Two to three weeks after, the pond can be fill with water.

Ix.4. THE FENCE
The fence prevents the entry of predatory of all species (snakes, frogs, otters…) in the enclosure
of the pond (Figure 98 and Photo M below). It can be made of a netting, that one buries on at least
a 10 cm depth and the higher end turned towards the pond. Metal stakes or of not very putrescible
wood are thus established all the 50 - 90 cm to be used as support with the grid fixed using wire of
fastener. For the bamboos, it will be necessary to think of their replacements after 18 months to the
maximum in tropical zone. Other materials other than netting can be used.

In all the cases, it is advisable to take care that
the fence does not have any hole on the whole of
its perimeter. The second role is also to limit the
poaching which is one of the important causes
of the abandonment of the ponds. The use of the
access doors in the enclosure of the ponds will
have to be, so controlled well.
If necessary, if the piscivorous birds are too
numerous, one can have recourse to the installa-
tion of a coarse net on the ponds and to the use
of scarecrows.

Photo M. Setting of a fences with branches
(Liberia) [© Y. Fermon].

Stream

Pond
Fishponds
Fisherman
Door B
Predators
Dikes
Thief Channel

Controle of water level A
Figure 98. Fences (A).
In scrubs (B); In wood or bamboo (C). C


3. PONDS
Ix.5. THE FILLING OF THE POND AND TESTS
As soon as possible and before the completion of the pond, it is advisable to put it under water:
Ö To check that all structures function properly such as the water intake, the canals, the pond inlet
and outlet;
Ö To check that the new dikes are strong and impervious enough;
Ö To accelerate the stabilization of these dikes.
For maximum security and efficiency, one willproceed in the following way:
1. Fill the pond with water very slowly and up to a maximum depth of 0.40 m at the outlet.
2. Close the water supply and keep water in the pond for a few days. During this period, check
the dikes carefully. Repair crevices and collapsed sections, compacting well.
3. Drain the water completely and leave the pond dry for a few days. Keep checking the dikes
and repair them as necessary.
4. Fill the pond again very slowly and up to a maximum level about 0.40 m higher than the
previous time.
5. Close the water supply. Check the dikes and repair them as necessary. After a few days,
drain the pond completely.
6. Repeat this process of filling/drying until the water level in the pond reaches the designed
maximum level.
7. Check and repair the dikes as necessary.

x. NECESSARY RESOURCES
x.1. MATERIALS
The initial stage of prospection and the picketing of the site requires only few material. It is about:
9 Stakes
9 Tie up and ropes
9 Decametre
9 Machete
9 Two-handed hammer
9 Plumb level or if possible, a theodolite or automatic level
9 Paper and pencils
Then, it is necessary to make the list of the technical descriptions, while referring in the topogra-
phic plans and the drawings of detail available. These descriptions must separately treat earthworks
and works, as indicated hereafter:
1. Descriptions of the earthworks:
(i) Preparing the ground of the site, in particular clearing and uprooting complete, handling
and placement of the cleared vegetation;
(ii) Removal of the layer of topsoil, with indication of its surface, its thickness and places of
storage;
(iii) Construction of the dikes, with indication of the source and the quality of the ground as well
as its characteristics;
(iv) Compaction of the dikes, with mention of the maximum thickness of the layers, the moisture
of the ground, the capacity and the type of equipment to be used
2. Descriptions of the structures, indexing the types and characteristic of materials to be
used in each case, such as:
(i) Reinforced concrete - type of proportioning, limits to be observed during the test of de-
pression, types of reinforcements, method of cure, formwork;
(ii) Wood - detailed list of the species, treatment, relative humidity, conditions of storage;


(iii) Bricks or breeze blocks - quality, finished external, standard, weight, conditions of storage;
(iv) Pipes - type, material, storage, handling, pose;
(v) Mortars and coatings, additives, water…;
(vi) Paintings - indication of the number of layers, the type of painting.
For the building work carried out with the hand, simple tools are necessary:
Hoe, shovel, machete, pickaxe, wheelbarrow and/or basket, matchet, buckets, axe, bar with
mine, dig, roller of wire, plumb level, ram, hammer, two-handed hammers, decametre, saw, screw
clamp;
In materials used and consumable:
9 Planks of wood,
9 Pipe PVC or out of galvanized iron,
9 Concrete,
9 Sand,
9 Gravel,
9 Concrete-reinforcing steel
9 Stakes,
9 Sheets of banana tree,
9 Oil of draining,
9 Painting.
In most of the cases, the needs for inputs will be only the pipe PVC and the concrete. It happens
that the concrete is not easily available. One will be able to then choose to make local brick or wood
structures improved in order to support the immersion. Time between two repairs is then likely to be
reduced, the concrete monks which can last more than 20 years.

x.2. HUMAN RESOURCES AND NECESSARY TIME
Work can be made by the beneficairies and the members of their family, with the assistance of
some friends if necessary. It is possible also, to accelerate the time of construction, to sign a contract
with daily workers to dig the pond by hand for a fixed price based on the volume of the earthworks.
Each pond generally does not have more than 400 m2 of surface. The volume of the earthworks
makes it possible to estimate time that each pond will be needed and, if necessary, to build the price
to envisage to sub-contract this task.

Table XX.Examples of necessary time for building of ponds (man/day).
1 pond of 400 m2 2 ponds of 200 m2 4 of 400 m2 and 2 of 100 m2
Main water supply 130 266 130
Water supply channel 50 (200 m) 50 (200 m) 70 (270 m)
Excavation/construction
600 (150 m3) 1600 (400 m3) 3600 (950 m3)
of the dikes
Inlet/Oulet 5 4 90
Total Time 785 1920 3890

Table XXI. Approximate output on the works of excavation made by hand.
Volume excavated (m3/j)
Nature of the soil With hoe With pickaxe / shovel
Soft (deposits, sandy soil) 2.5 – 3.0 3.5 – 4.0
Moderately hard (silt, light clay) 1.5 – 2.0 2.5 – 3.0
Hard (heavier clay) 1.0 2.0 – 2.5
Lateritic, moderately hard 0.5 1.0 – 1.5
Water saturated 0.8 – 1.5 1.5 – 2.0


3. PONDS
The standards of work relating to the earthworks carried out with the hand will depend mainly
on the nature of the ground. The harder it is to work and the less high the outputs are. The presence
of water in excess results also in to reduce the outputs, in particular in the presence of clays heavy
and sticking
One will see in Table XX, p. 110 examples of duration for each section of work. Times strongly vary
and are given only as an indication. For example, a pond of 200 m2 took 20 days full for 20 people,
that is to say a total of 400 men per day (8 work hours manpower per day) in Liberia. In Cameroun,
for a complete exploitation of 2 ha with 15 ponds of 400 m2 each one, a eclosery of 10 x 10 m2, an
office plus a store of 150 m2, 5 hen houses and 5 pigsties, time was of 226 men per day by pond.
This corresponds to a total of 3435 men per day for the whole of the exploitation.
Standards of work applicable to the excavation work carried out with the hand are indicated to
Table XXI, p. 110. They are the average outputs to the excavation and the throw at a distance from 1 m
which one can discount of medium worker who carry out earthworks during eight hours per day: the
minimal values correspond to the use of the hoe and the maximum values with the use of the pickaxe
and the shovel under similar conditions. These outputs must be slightly reduced when the distance
from throw increases. For work of excavation and shaping of the channels, the output of a qualified
digger varies from 0.8 to 1.2 m3 day. One can estimate the duration of the work overall, but for each
case, one will have to recompute this calendar according to the means available (Table XXII below).
If the number of workers is sufficient, several stages can be done in same time.
In time, it is desirable that the earthworks are done at the time when the costs of construction
will be weakest. The most favourable moment is thus the dry season, especially at the end of the
season for the earthwork. At this time, the bearing pressure of the ground is better and the swamps
are not saturated of water. For the programming of work, one thus designs a calendar in which the
programming of each task will appear (Table XXIII below).

Table XXII. Example of calendar of works to do for the construction of a pond
(workers of 400 men per day). Activities in dark.
For 3 or 4 ponds For 1 or 2 ponds
Activities/Week
1 2 3 4 5 6 7 8 1 2 3 4
Clear vegetation
Remove topsoil
Dig supply channel
Build main water intake
Build the main draining structure
Build the outlet
Build the inlet
Build the dikes
Finalising the pond

Table XXIII.Example of calendar according the seasons (15 ponds) in Cameroon.
Activity/Month Sept Oct Nov Dec Jan Feb March April May June July Aug Sept
Clean the site
Topographic
plan
Design setting
Water supply
Excavation
works
Other


One will see in Table XXXVI, p. 169 of the examples of management for 4 ponds for a construction
of approximately a month (400 men per day). Cleaning can take less time if the labor is sufficient to
ensure several building sites at the same time.

xI. SUMMARY

Ö All of the operations being carried out can be summarized in the following figure:

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas

Duration:
Completion and filling in water
3 to 6 months

Ö Emphasis on:
Ö The cleaning of the site that must be done well
Ö The picketing which must be precise for the slopes
Ö The control and management of the water by channels
Ö The importance of dykes, their strength and their size and although compacted
Ö The choice of a monk for draining ponds
Ö The total isolation of the ponds from the outside for better control
Ö The soil conservation upstream


Chapter 08
BIOLOGICAL APPROACH
The pond is now in water. So, the biological aspects can start (Figure 100, p. 114).
A pond is an environment that will turn on itself. It will need to ensure the start and development
of the biological cycles.
Following the construction of the pond, the following stages will be:
12. Fertilization
13. Waiting for a « green water »

I. THE LIFE IN A POND
The pond is a small ecosystem with several trophic levels comprising the micro-organisms and
algae, the plankton, the insects and larvae of insects. Then, the fish which are the important compo-
nent that one wants to make grow in an optimal way (Figure 99 below).
Plant photosynthetic organisms are the only living organisms able to transform mineral matter
into organic matter. The development of complex molecules requires energy which the plants col-
lect from solar energy. The organic matter is initially produced from minerals by the photosynthetic
plants. Thereafter, it can be assimilated and transformed by the animals. The animal organisms
consume organic matter to grow, they are unable to develop from minerals. The organic matter
(vegetable debris, dejections and dead animals), is decomposed and mineralized and turns by this
process to mineral matter. It is estimated that one needs 1 kg of phytoplankton to obtain 10 g of fish
like tilapia (Figure 101, p. 115). The population of each trophic level must indeed be definitely higher
than that of its predators to be able to renew itself.
Green: Producer Photosynthesis
Black: Consumer Assimilation
Sun light
Brown: Decomposer Predation
Decomposition
Hydrophytes
aquatic plants
Plankton
Minerals NPK Phytoplankton
(Nitrogen,
Phosphorus...)
Zooplancton
Algae

Nekton

Small
invertebrates

Benthos
Bacteria

Figure 99. Schematic life cycle of a pond.


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining

Figure 100. Setting of fish pond: 4. Fishfarming.


4. FISH FARMING

Tertiary consumers
1 g
Super-carnivores

Secundary consumers
10 g
Carnivores

Primary consumers
100 g
Herbivores

Primary producers
1000 g
Plants, phytoplankton

Minerals Organic
Nutrients Decomposers debris

Figure 101. Trophic pyramids.

I.1. PRIMARY PRODUCERS
The most important group of vegetable organisms in a fish pond is the phytoplankton. It is
composed by a wide variety of aquatic algae which are free in water (without substrate). These
algae are made up either of a cell (unicellular) or several cells (pluricellular) (Figure 102 below). Their
presence in very great number gives blue green to maroon green color to the water of the pond. The
phytoplankton has two very important functions in a fish pond. Firstly, it is an oxygen producer and
secondly, it is the first link of the food chain in a fish pond.
Algae are photosynthetic organisms that convert light energy into chemical energy, while consu-
ming carbon dioxide (CO2) at night, like any organism and producing oxygen (O2). This process oc-
curs only during the day with the presence of sunlight. The life of these organisms is relatively short
and phytoplankton biomass vary with the characteristics of the environment such as temperature,

10 µm
Filamentous algae

1 mm
10 µm 10 µm
Unicellular algae Colonial algae Multicellular algae

Figure 102. Differents algae.


presence of mineral elements, the illumination…
Emerged Float Submerged
plants plants plants The filamentous algae in too great concentration
are to be removed in the ponds.
If the mass of the vegetable organisms (phy-
toplankton and aquatic plants) in the pond is too
important, it can consume oxygen at the expense
of fish growth. At dawn, one can observe fish co-
ming to seek oxygen at water surface and even
sometimes, a massive mortality by asphyxiation.
Figure 103. Aquatic plants The higher plants can become serious indi-
(To avoid in ponds). rect competitors of the fish production in pond,
either by breathing during the night, or by the
consumption of minerals, or finally by the shelter which they offer to the predatory organisms. The
immersed plants, the emerged plants and the floating plants are distinguished (Figure 103 above).
They are generally not useful in the pond except for the farming of herbivorous fish. By the use of mi-
nerals, these elements are not available any more for the phytoplankton, basic link of the food chain
of the pond. In the same way, the cover formed by the higher plants decreases the penetration of
the light in water, which reduces the capacities of photosynthesis of the phytoplankton and thus its
development. The presence of some herbivorous fish can limit their proliferation. So in spite of these,
the higher watery plants appear, it will have to be removed as quickly as possible.

I.2. THE INVERTEBRATES
The algae are used as food with the micros-
copic herbivores: the zooplancton. Itself feeds
the consumers of 2nd order: carnivores. They
consume wastes, phytoplankton, bacteria and
for largest, other zooplanctonic organisms.
Many organisms live close to the bottom
which one calls benthos.
I.2.1. THE ROTIFERS
Rotifers are small organisms measuring
between 50 µm and 3 mm which often have the
shape of trumpet, cylindrical or spherical. They
have two crowns of lashes around their mouth
as well as an organic system specialized with in
particular a digestive tract. They neither are seg-
mented nor metamerized. The body is covered
laterally by a resistant cuticle which sometimes
becomes a true shell.
They live mainly in freshwater but some spe-
cies occupy marine waters as well as wetlands.
They feed mainly on micro-organisms in suspen- Figure 104. Rotifers.

Adults

Juveniles

Small size Big size
Pest Cladocerans Copepods

Figure 105. Crustaceans.


4. FISH FARMING
sion in water. Some rotifers are parasites of crustaceans, molluscs and annelids. They compose
most of the zooplankton of freshwater and constitute a source of important food in the fresh water
ecosystems (Figure 104, p. 116).
I.2.2. THE CRUSTACEANS
Part of the organisms
composing the zooplan- Adult Larvae
kton are small crusta-
ceans which are mainly
divided in two classes, in
ascending sizes. It dis-
tinguishes the cladocers
and the copepods (Figure
105, p. 116 ). The zooplan-
kton form an excellent Dytiscus
food for many fish spe-
cies especially during the
larval stage. However, the 4 to 8 mm
largest copepods are pre-
dators of eggs, larvae and
even of fry. It is important
to know the dynamism
of development of the Dragonfly
groups composing the
zooplankton. One will be
able to also find in water 10 to 20 mm
some crustaceans which
are parasites of fish and
predators. Moreover, the
presence of crabs and
shrimps are not to exclude Figure 106. Insects.
if they pass the filter.
After the setting in water of a well fertilized pond, one ob-
serves during the first days a good development of the popula-
tion of the class of smallest zooplankton, the rotifers. It is only
after one week that the population of the cladocers reaches its
optimum and the same, after ten days for the population of the
copepods.
I.2.3. THE INSECTS
A large part of the aquatic invertebrates are insects (Figure
106 above). Most of the time they are larvae such as mosquitos,
dragonflies, flies, ephemers, trichopters… which have a phase of
larval aquatic life and, after emergence, will spawn in water. By
this cycle, some are vectors of serious human diseases like mala-
ria (mosquito) either the onchocerciasis or river blindness (simu-
lis). Some also are predators of fry.
Some insects have an aquatic life as adults like the water
beetles (Dytiscidae) and the water scorpions (Nepidae). They are
also, often the predators of fry.
I.2.4. THE MOLLUSCS
There are a number of aquatic molluscs (Figure 107 opposite).
You can find water snails and mussels Anodonta or freshwater.
Snails can be predators of fish eggs. They are also the vector of a
parasitic disease, schistosomiasis. Figure 107. Molluscs.


I.2.5. OTHER INVERTEBRATES
Other aquatic organisms can be found hydraires, parasitic worms (helminths, platyhelminths),
leeches, sponges and even jellyfish. Some are predators of fish fry.

I.3. THE VERTEBRATES
Among the vertebrate ones, it is clear that the most represented are the fish with more than
10 000 freshwater described species in the whole world. One will reconsider the biology of some
useful species in fishfarming.
One will find also, well represented, the amphibians as frogs and toads which have an aquatic
larval phase (Figure 108 below). Many tadpoles are herbivorous, but there are some which are pre-
dators and can feed on small fish.
Among the reptiles, several snakes like the grass snakes and certain turtles are predators of fish.
Finally, there exist several species of piscivorous birds like the kingfishers, the pelicans, the cor-
morants, the eagles, the herons which are effective predators of juveniles and adults fish.
Finally, a mammal, the otter, which is a large fish predator.

Amphibians Reptiles Birds Mammals
(frogs) (snakes, turtles) (eagle, herons) (otter)

Figure 108. Vertebrates other than fish.

II. THE FERTILIZATION
A clear natural water does not contain a food for fish. The water of the pond is like the agricultural
land: if the ground is fertile, the plant grows well. To make water fertile, it is necessary to bring there
fertilizing elements of which phosphorus in priority. A water will answer much better to the fertiliza-
tion when its initial physical and chemical characteristics (temperature, pH, dissolved oxygen…) are
close to the optimal ranges of the selected species. The fertilization is to increase the production of
natural food in a pond, which makes possible to the fish to find what to feed itself in larger quantity.
The fertilization consists in providing food to the living organisms of the pond which will be used as
food for fish.
When one uses manures to increase the fish production of the ponds, one will try to establish
and maintain a dense population of phytoplankton and zooplankton, which should give a beautiful
green color to water

II.1. THE FERTILIZERS OR MANURE
The action of organic manures is a little more complex. One distinguishes at least three functions
for this type of manures which are (Figure 109, p. 119):
Ö To be used as fertilizing matter,
Ö To be useful partly, of direct food for some fish species as tilapia, but also for part of fauna living
in the pond,
Ö To be used as support for a range of populations of microscopic organisms, part of fish natural
foods.
The fertilizing function of the organic manure is progressive because the minerals contained in
this manure are made available to the phytoplankton only progressively of its decomposition until its
complete mineralization.
Several kinds of organic matters, most of the time of waste, can be used like organic manures.


4. FISH FARMING
Most current are the following ones:
9 Animal manures, mostly from the ani-
mals of the farm;
9 Waste of slaughter-house;
9 Fermentation of cassava;
9 Natural vegetation;
9 Compost, a mixture of various kinds of CO2
organic matters.
II.1.1. ANIMAL MANURE
CO
They constitute an additional source of car- 2

bonic gas (CO2), which is very important for the Zooplankton
effective use of the nutritive elements present
in water. They increase the abundance of bac-
teria in water, which accelerate the decomposi-
Bacteria
tion of the organic matters, and are also used
as food for the zooplankton, which in its turn
also increases in abundance. They have bene-
ficial effects not only on the structure of the soil
of the bottom of the pond but also on benthic
fauna like the larvae of chironomids. However,
the animal manures have some disadvantages,
most of the time related on their low content of Benthic fauna
primary nutrients, for their negative effects on Figure 109. Beneficial effects of
the dissolved oxygen content and to the reserve organic fertilizers.
of some fishfarmerss to use livestock wastes di-
rectly in the fishponds. The chemical composition of the organic manure varies considerably accor-
ding to the animal of which it comes - with knowing the species, the age, the sex, its type of food
- and according to the way in which the manure is treated, i.e. its relative freshness, the conditions
of storage and the dilution rate with water. Chicken droppings are very rich in nutritive elements.
The dejections of pig are usually richer than those of sheep or goat. The dung of cow and horse are
poorer in nutritive elements, in particular when the animals eat only grass. Their fiber contents are
relatively high. The excrement of buffalo is the poorest manure of all.
The manure should be easy to collect. The animals under shelters or in enclosure produce a
manure more concentrated than those which are in freedom. One can design the shelters of animals
in order to improve the collection and the distribution of the manure towards the ponds.
The sources of animal organic manure are rather numerous, but often in rather small quantities
(Table XXIV and Table XXV, p. 120). This includes:
9 The chicken droppings and other birds are dispersed often too much in rural environment to
be exploitable in the large ponds.
9 Manure of pig which is usable only by non Muslims. Association pigsty and fishfarming are
very interesting by the outputs and the facilities which it gets. One will let dry this manure during 2
weeks before using it.
9 The manure of cow and other ruminants which is to be used with many precautions because
they are too rich in cellulose and risk to cause an important fermentation which will make fall brutally
the oxygen rate. It is preferable to use it in application on the bottom of the ponds, dry after draining.
A scarification of the plate makes it possible to mix the manure with the mud without turning over
the ground.
9 Liquid manure is a liquid oozing of a heap of manures after a rain or a watering is only found
in the breedings where one collects the urines and the manure. It is excellent for the production of
zooplankton at a rate of 2.5 liters/are/week. In the event of ammoniacal odor, it is necessary to re-
duce the amounts by half.
The amount of animal manure to apply in a given pond varies considerably according to factors


like the climate, the water quality and the soil, the characteristics of the manure and the type of
regime (standard fish, density of fish, length of the period of farming). It is, however, impossible to
recommend a treatment which is valid in all circumstances.
Spreadings must beings uniform to avoid any annoying concentration. The choice of manures is
fixed by the availability and the price, if possible no one. Each manure must be the subject of tests
to check its productivity and its not-harmfulness. The spreading of droppings is carried out prefe-
rentially in weight of droppings and expressed as a percentage of the fish biomass. Should not be
exceeded the recommended maximum values. This to initially avoid an accumulation at the bottom
of the pond and then a fast fall of the oxygen rate. The ideal frequency of the contributions follows
the rule: as often as possible. Best is a daily application. As an indication, in the small rural ponds
of 100 m2 to 300 m2, the distribution is done once, or preferably twice by week. If one does not use
of the manure every day but only once per week, that does not want to say that it is necessary to
spread of them seven times more in only once in the pond.
II.1.2. OTHER ORGANIC MANURES
Several organic manures others that the animal manure are usually used on the fishfarm of small
size. These manures are usually waste which one can get for few expenses and locally. Organic
manures most usually used are:
Ö Waste of slaughter-house, such as contents of bovines rumen, blood, bone and enriched
waste water.
Ö Agro-industrial waste, such as seeds of cotton, molasses, oil cake oilseeds and residual palm
oil mud (4 to 5 % of nitrogen). Waste like the rice balls, bagasses of sugar cane and the sawdust are
rich in cellulose, which decomposes very slowly in the pond.
Ö Retting of cassava. Cassava tubers of the bitter species that one can let soak in the ponds to
remove the hydrocyanic acid from it before consumption, constitute an excellent way and at a cheap
rate to fertilize the small ponds. The cassava then is recovered and consumed. The fertilization
comes from the juice of steeping and is thus free. A minimum contribution of 10 kg tubers/are/day is
recommended. The amount can reach 200 kg/are/week but no more.

Table XXIV. Maximum amount of fresh solid manure per day in 100 m2 pond.
Solid manure Maximum amount (kg fresh/100 m2 /d)
Duck 2.8
Poultry
Chicken 4.8
Pigs Pig 6.0
Small ruminants Sheep/Goat 3.4
Buffalo 6.3
Large ruminants Cattlel 6.0
Horse 5.2

Table XXV. Quantity to spread per type of manure.
Quantity For a pond of 400 m2 % fish
Source
(kg/100 m2) (4 ares) biomass
Poultry Poultry droppings 4.5 ½ to 1 wheelbarrow/week 2à4
Pigs Pig dung 6 ½ to 1 wheelbarrow/week 3à4
Small ruminants Sheep or goat dung 3
Cattle or horse dung 5
Cattle or horse stable-litter 15
Large ruminants
Manure of large ruminants 1 tonne/year
Liquid manure 10 l/week


4. FISH FARMING
Ö The vegetation which was cut in the pond itself, the channels or other water places. In some
areas, harmful floating plants like the water hyacinth (Eichornia crassipes), the water ferns (Salvinia
sp.) and water lettuces (Pistia sp.) can be used effectively.
Ö The compost produced apart from the ponds can be spread out over the bottom of the pond
drained before the filling, or be used regularly to fertilize water. The vegetation such as graminaceous
crossed, vegetation wastes and fruits in decomposition can be used to manufacture a simple com-
post in the pond itself.
The average quantities of these organic manures to apply to the small ponds are indicated in
Table XXVI (below). They should be used regularly, while avoiding overloading the pond for several
weeks. It will be necessary to check water quality to adjust the quantities used.

II.2. THE COMPOST
Composting is characterized by the intensive decomposition by organic matter micro-orga-
nisms, in general under controlled conditions. This process allows to use a whole range of waste,
residues and natural vegetation at a cheap rate for the production of a clean product, dry and rich in
primary organic matters and nutritive elements. This product is called compost.
The manufacture of compost is carried out via various groups of micro-organisms as bacteria,
mushrooms and protozoa, which need mainly carbon (C) and nitrogen (NR) for their development.
It is to obtain these substances which they decompose the organic matters available. The compost
are composed of relatively tender plants like the leaves, grasses and aquatic plants, which one mixes
with feces (of birds, pigs, herbivores or human).
The compost can be produced under anaerobic conditions (in the absence of oxygen) or aerobic
(in the presence of oxygen). Each type shows specific characteristics (Table XXVII, p. 122). In some
agricultural systems, one uses the two types of composting, for example the aerobic preparation in
the parts external of material and the anaerobic preparation in the interior zone where there is little
oxygen.
In fishfarming, composting is usually practiced in two ways:
Ö Simple composting aerobic/anaerobic underwater, in heap.
Ö Dry composting aerobic, either in heap, or in pits.
To prepare the compost on ground, it is easier to use the aerobic method (Figure 110, p. 123). It is
then important to ensure that there is always air in the heap of compost to maintain a fast and total
decomposition of organic matters. For this purpose, the stages will be of:
1. To start to constitute a new heap of compost while placing a first layer of coarse vegetable
matters, for example of the rachis of leaves of banana tree, straw or stems of sugar cane, on a height
of at least 25 cm. This layer should allow the circulation of air while absorbing the liquids rich in nu-
tritive elements coming from the upper layers.
2. To cut the matters used for the compost of small pieces from 3 to 7 cm.

Table XXVI. Organic fertilizers commonly used in small-scale fish farming.
Organic fertilizer Average amount applied at regular intervals
Animal manures See Table XXIV and Table XXV, p. 120
Slaughterhouse wastes 10 kg/100 m2/week
Agro-industrial wastes 8 kg/100 m2/week
50 to 100 m3/week
Cassava tubers
10 to 25 kg/100 m2/day
Vegetation 20 to 25 kg/100 m2/week
20 to 25 kg/100 m2/week
Compost
50 kg/100 m2 pond bottom


3. To pile up without packing all the matters, by leaving space between the layers. One never
should compact the heap of compost. One should not make a too high heap to avoid a packed
under its own weight.
4. To maintain the heap moist but not wet. Too much water would prevent the air circulation. It will
be necessary to protect the heap from the rain (too much wet) and the sun (too much dry).
5. To turn over the heap of time to other to air it and avoid a production of too intense heat in the
center. One introduces a piece of wood in the middle of the heap and one waits a few minutes before
withdrawing it. If the heap is too hot, dry or too odorous, it is time to turn over it
There are two ways of piling up materials:
Ö In heap above the level of the ground, preferably during the seasons of strong rain. It will be then
easier to turn over and maintain ventilated, but the carbon and nitrogen losses are high, or
Ö In pits dug in the ground, a place raised to avoid the floods. They will have to be protected by
trenches, if necessary. It is preferable under dry climates to retain moisture. The carbon and nitrogen
losses are weaker.
II.2.1. THE LIMING
The earth ponds are conditioned by liming, i.e. by preparing the ponds and by treating them with
various types of amendments limestones, chemical substances rich in calcium (Ca). Liming improves
the structure of the ground of the pond, improves and stabilizes water quality and allows that ma-
nures are more effective to increase natural food available. One of the most important effects, that
one can measure and use to control liming, is that which modifies the total alkalinity of the water of
the pond. The total alkalinity of water is the measurement of its total concentration out of carbonates
and bicarbonates of substances like the calcium (Ca) and the magnesium (Mg) which are typically
alkaline.
The liming of the ponds is not always necessary. One can do it on a new pond or a pond already
used. In certain cases, it can not only be one money wasting, but also prove to be harmful with fish.
Before making a decision, the pond will have to be studied attentively as well as the particular cha-
racteristics of its water and its ground. The following points will be checked:
9 If the pH of the ground of the bottom of the pond is lower than 6,5, liming is justified.
9 If the bottom of the pond is very muddy because it regularly was not emptied and was drai-
ned, liming will improve the conditions of the ground.
9 If there is risk which a contagious disease propagates or if it is necessary to fight against of
the enemies of fish, liming can help, in particular in the drained ponds.
9 If the quantity of organic matters is too high, either in the ground of the bottom, or in water,
liming is advised.
9 If the total alkalinity of water is lower than 25 mg/l CaCO3 liming can be justified.

Table XXVII. Particular characteristics of composting methods.
Characteristics Aerobic composting Anaerobic composting
Presence of oxygen Necessary No
Losses of nitrogen Important Reduced
Losses of carbon Important Reduced
Production of heat Important Very small
Destruction of pathogens Yes No
To be controlled,
Moisture content Not importante
best 40-60%
In heap, above ground level In heap. deeper under water
In sealed heap, above ground
Composting method In pit, below ground level
level
In heap, at water surface In sealed pit, below ground level


4. FISH FARMING

Air should always be
present within the
composting pile

keep moist
Pile not too high but not wet

Finely cut and loosely
Protect from sun packed material
and rain
AIR

25 cm First layer:
very coars material

Check composting process: … if too hot or smelly,
drive stick in… turn pile over

Pile up composting material… …or in pits

Figure 110. Preparation of dry compost.


The effects on the ground of the bottom of the pond are:
Ö An improvement of the structure;
Ö An acceleration of the decomposition of the organic matters;
Ö An increase in the pH.
All these factors will involve a faster and more important exchange of minerals and nutritive
elements between the ground of the bottom of the pond and water, at the same time a reduction in
the demand for dissolved oxygen.
Usually, the amendments limestones and manures are applied separately. It will thus be neces-
sary to lime at least two weeks, and preferably a month, before any spreading of manure. Annual li-
ming will thus be carried out at various times of the year according to the calendar of management of
the pond. In tropical climates, it is preferable to lime the pond as soon as the fish was collected and
at least two weeks before putting fish again. Manures are applied then, 15 to 30 days after liming.
However, measurements of the pH and alkalinity, even if they are current, will not be inevitably
accessible for the recipients, who will be able to then address themselves to local laboratories and
institutes. For NGOs, kits of analyzes are easily available in the trade and not very expensive.
II.2.2. THE SPREADING
It is possible to spread manures either dry, or when the pond is fill of water.
A certain number of methods concern the site and the distribution of the animal manure in va-
rious situations (Figure 111, Figure 112 and Figure 113, p. 125). However, the illustrated examples are
general and must be adapted to the local conditions (quality and quantity of manure available, water
quality, weather conditions…).
Except for waste of slaughter-house and tubers of cassava, organic manures are thus piled in
one or more heap in water. One can also use an enclosure in a corner of the pond. Organic manure
is piled up and compacted inside, in order to start a production of underwater compost. It had been
already seen how to make compost in aerobic. One can have a compost in anaerobic (paragraphe
II.2, p. 121).
For that, in each pond, one arranges a composting heap in bamboo or wooden to retain manure.
One will place it in an angle, in the major part of the pond (Figure 115 and Photo N, p. 126). The heap
must be well packed underwater, for example by trampling each layer carefully (Figure 114, p. 125). But
it will have to exceed water surface slightly, since its height will decrease slowly. Each week, it is
necessary to add new layers of matters to reconstitute it. To obtain very good performances:
Ö To use at least a heap of compost by 100 m2 of pond.
Ö To take care that the total surface area of the surface of the enclosures with compost corres-
ponds to 10 % of the surface of the pond.
Ö To turn over the heaps all both or three days.
Ö To place the sufficiently deep water heaps.
II.2.3. THE «GREEN WATER»
Once the ponds out of water and are fertilized, it thus should be waited until the natural cycle of
the pond is set up. For that, one will wait several days during which, in the event of good fertilization,
water will become green, i.e. rich in phytoplankton. To know if water is sufficiently green, one can use
a disc of Secchi (paragraphe II.1.2, p. 48) or quite simply to plunge the arm in the pond to the elbow.
If one distinguishes hardly the end from the fingers, it is that water is sufficiently green.
The pond is now ready for receiving fish.


4. FISH FARMING
In heaps In rows

A B C D
Figure 111. Applying animal manures to a drained pond bottom. A: New pond;
B: Pond in which the water is badly controled;
C and D: Pond in which the water is well controled (most common case).

10 m

1m

A B C D
Figure 112. Applying animal manures to water-filled ponds that have been stocked (I).
A: Distribution of liquid animal manure from the banks; B: Distribution of animal manure
using an inner-tube and basket; C: Disposition in heaps along the banks;
D: Detail of an elongated crib.

A B

Figure 113. Applying animal manures to water-
filled ponds that have been stocked (II).
A: Stacking animal manure mixed with stable-
litter in heaps along the banks;
B: Applying pure animal manure from a boat.

Fill up to the surface of
the water and well
compress

Figure 114. Preparation of an anaerobic com-
post.


Installation of a crib in
each of the two shallow
corners

Photo N. Compost heap. [Up, Liberia
Figure 115. Compost heap in crib in a pond.
© Y. Fermon], [Down, © APDRA-F](CIRAD).

III. SUMMARY

Ö The two steps are:
Ö The fertilization
Ö The expectation of a « green water » which indicate that the pond is ready for
ensemensement
Ö Emphasis on:
Ö The preparation of aerobic and anaerobic compost


Chapter 09
THE HANDLING OF THE FISH
Once the pond is ready, stocking may take place (Figure 116, p. 128).
The reader will find in Appendix 04 p. 239 information on the species of fish used in fish farming in
Africa according to the basins and countries. Consider again the sequence of operations, activities
will be in the following order:

14. Collecting tilapia
• In the field
• By propagation
15. Juveniles storage
16. Transporting live fish
17. Stocking tilapia
18. Following the fish
19. Stocking with other species
20. Draining and harvesting

In a certain number of cases and areas, it is rather easy to get tilapia fingerlings in the wild.
Otherwise, one will choose to produce fry from broodstock collected in the wild. The assessment
previously carried out will indicate which are the species usable close to the selected sites:
Ö To limit the loss of fish;
Ö To limit the costs. A transport on long distance requires a logistics which can be costly. One will
try to limit the maximum displacements.
Insofar as the majority of the fingerlings producers currently in Africa do it without real
genetic management of the broodstock and, moreover, starting from introduced species, and
in order to limit the costs, one will avoid most of the time providing oneself in fingerlings from
local producers

I. CATCH METHODS
On a fish farm, live fish have to be handled on many occasions, for example during routine
monitoring of their growth and health, transfer from one pond to another and final harvesting. This
handling usually involves the use of various nets and other small pieces of equipment.
However, it is necessary to remember some points mentioned above.

Ö If they are beneficiaries who will make the catch, the difficulty will be to make them
understand that it is not necessary to look for fish elsewhere than at home.
Ö One of the main principles will be to use only non-destructive gear for the local wildlife.
Ö Care should be taken to respect the laws relating to fishing. Where appropriate, per-
mits have to be requested from the local authorities.

To get wild specimens, the help of local fishermen who can be, sometimes, also beneficiaries
can be requested. In general, they know well the places of possible capture of the various species.
If necessary, one will be able to manufacture small fishing gears.


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining

Figure 116. Setting of fish pond: 4. Fishfarming and 5. End of cycle.


4. FISH FARMING 5. END OF THE CYCLE
I.1. SEINE NETS
One of the main gear to catch is the seine. Head rope
It is the easiest way to catch fry. If a seine of with floats
meshs of approximately 1 cm is used, the fish
catch will have at least 5 cm length. To collect
juveniles, one will use seines made with mos-
Mounting twine
quito net.
A seine net is the most common type of net
used on fish farms to harvest fish. It is a long net
with ropes at each end and is pulled along the
pond to collect the fish and then drawn into a
circle to trap them and, most often, bring back Netting
Depth of net
to the shore.
A seine net consists of one or more pieces
of netting material mounted (Figure 117 oppo-
site):
9 At the top on a head rope equipped
with floats; Mounting twine
9 At the bottom on a foot rope equipped
with sinkers (or leads).
Foot rope with
These ropes are normally extended beyond sinkers
the netting to form pulling ropes.
There are several kinds of seine. The two
following designs are most commonly used. Figure 117. Diagram of a seine.
Ö The seine is made similarly over all its
length. It consists of a single rectangular netting panel.
Ö The seine is made of three parts:
¾ One central, loosely mounted bag to collect the fish;
¾ Two lateral wings to lead the fish towards the central part.

To be able to make a net, various materials are necessary (Figure 118, p. 130).
Rope can be made either of natural fibre (hemp, manila, sisal) or synthetic fibre (polyamide,
polyethylene or polypropylene). Synthetic fibres are stronger and more resistant. Rope can be either
twisted or braided.
Floats can be made of several materials such as light woodpaint or tar it to keep it from beco-
ming impregnated with water, which would reduce its floatability; cork; plastic.In short, of a material
which floats
Sinkers are usually made either from baked earth or lead. In this last case, they are available as
thin lead sheets or in the form of olives of various individual weights. Lead recovered can be used. A
total weight of sinkers equal to 1 to 1.5 times the total floatability of the floats is need. Small stones
can also be used, but they may break more easily.
For the assembly, one will put a float every 10 to 25 cm maximum. For the sinkers, one every 3
intervals. Various stages are necessary to mount a seine (Figure 118, p. 130).
A small seine may be handled by as few as two people, one at each end of the net, who hold the
net vertical with the wooden poles (Figure 119, Figure 120 and Figure 121, p. 131 and Photo O, p. 132). f
no poles are used, take care to keep the bottom rope slightly ahead of the top rope. With a muddy
pond bottom or with a larger and heavier seine, additional strength may be needed. In this case, one
person pulls at each end pole of the net while others assist by pulling at the extended end ropes. It is
useful to have an additional person standing near the middle of the seine while it is being handled to
help whenever necessary, for example when it gets stuck on some underwater obstacle.


Netting material Seines can be rather expensive
Net
pieces of equipment. To keep them in
Rope Netting
Twine needle good condition a good care of them
Float Sinker
should be take. Watch especially for
the following.
A
Protect them from direct sunlight
Head rope 6 mm in diameter and dry them in the shade.
and 11 m long After seining, clean and rinse them
well, removing all debris and fish slime,
String floats on the head ope
scales, etc.
150 Protect them in a cool, dry place
and tie the rope between two cm
posts such as an open shed.
Protect them from rats and mice,
B for example by hanging them on hori-
Attach netting material Non-slip Normal zontal bars above ground level.
with a net needle knot knot Repair them regularly. Replace a
section of netting it necessary.

C D
Begin to attach netting to
the head rope Ö Note that the use of seines is
generally prohibited in the wild.
9 meshes 8 meshes 8 meshes
If this is not the case, it will have
to be used only for the harvest
of fingerlings or broodstock. If
Float applicable, authorization must
E be obtained from the competent
authorities.

Upright wooden pole
Tie the foot rope
between two posts 20 to
and begin to attach 30 cm
bottom part of
netting

F
Head rope Placement of floats and sinkers First float
43 2 1 4 3 21 4 3 21 4 3 21
with floats
Tie side
Tie side rope
rope to
next to frst
pole
knot

Side
rope Join the head and
Foot rope 3 2 1 3 2 1 3 2 13 2 13 2 1 3 2 1 Notch foot ropes and add a
with sinkers pulling rope
G First sinker

Figure 118. The differents steps to construct Figure 119. Setting of the pole
a simple seine. to hold the seine.


8 m 7 m 8 m

2 m
1.30 m Wing Aile 1.30 m

Central section

When the three parts are assembled a bag
shape is formed in the central section
23 m

Bag shape

Figure 120. Construction of a central-bag seine.

Pulling the seine
Larger and heavier
from both sides of
seine nets will need
the pond
more people to
handle
A A

Two people using Keep the fish in the net Take in the net and
a small seine to and move it towards enclose the fish in a
catch fish the bank pocket

B C D
Transfer the fish to
a container using
a hand net

E E
Figure 121. Manipulation of a seine.


Photo O. Use of small beach seine (Liberia, Guinea, DRC) [© Y. Fermon].

I.2. GILL NETS
One of the most widely used nets in fres-
hwater capture fisheries is the gill net, which
may also be useful on a farm for selective har-
vesting of larger fish for marketing.

Photo P. Mounting, repair and use of gill nets (Kenya, Tanzania)
[© Y. Fermon].


Take a fish the
size you want to
catch and tie a
piece of string
around its
thickest part…

…the mesh size should be a
little less than this

A gillnet stretched between
two posts in midwater

Figure 122. Gill nets.

A gill net is very similar in overall shape and design to a seine net. The netting twine is thinner
and usually made of synthetic monofilament such as polyamide monofilament with a diameter from
0.12 to 0.25 mm, depending on the opening of the mesh. Mesh size is determined by the size of fish
to be harvested.
Fish should be able to pass through the extended mesh just beyond their gill covers but not
further. (Figure 122 above and Photo P, p. 132). When they feel caught and try to back out of the mesh,
their gill covers should be caught by the mesh sides (thus the name gill net). Such nets are highly
selective. The mesh size is calculated by measuring the body perimeter, or girth, of a few fish of the
size you wish to harvest. Your gill net should have a stretched mesh size about a quarter smaller than
the fish girth. Gill nets of stretched mesh size less of 4 cm or de 2 inches have to be avoid, for not
catching too small fish. It is important to check and remove the gilled fish maximum every hours
if one want to get the fish alive and not too damaged.

I.3. CAST NETS
Another non-destructive fishing gear and often used by the fishermen for the fish capture is the
cast net. It is quite useful to capture fish of large size without damaging them.
A cast net consists of a flat circular piece of small-mesh netting heavily weighted along its pe-
riphery with sinkers. Usually a series of strings run from the outer edge through a central ring to join
into a single pulling rope. As it is not very easy to make, you can buy your cast net from a specialized
store.
Skill is required in the handling of a cast net (Figure 123 and Photo Q, p. 134). It should be thrown
well opened and horizontally on to the water surface. It sinks rapidly to the bottom, and is closed by
pulling on the central rope, entrapping the fish inside the net.
A cast net can be used either from the banks, in the water or from a boat.


Open Closed
net net

Use a castnet
in the water

Photo Q. Cast net throwing (Kenya, Ghana)
[© F. Naneix, © Y. Fermon].

Use a castnet
from a boat

In position Closed

Figure 123. Use of a cast net.

I.4. DIP OR HAND NETS
Dip nets are commonly used on fish farms for handling and transferring small quantities of fish.
They can be bought complete, assembled from ready-made parts or you can make the nets yourself.
A dip net is made of three basic parts (Figure 124 and Photo R, p. 135):
9 A bag, made of netting material suitable in size and mesh type for the size and quantity of
fish to be handled;
9 A frame from which the bag hangs, generally made from either strong galvanized wire or iron
bar (usually circular, triangular or «D» shaped, with fixing attachments for the handle);



Round

Square or rectangular

Half-round

Handle
Frame

Bag
Photo R. Dip net (Guinea) [© Y. Fermon].

9 A handle, made from metal or wood and
0.20 to 1.50 m long, depending on the use of the Figure 124. Different types of dip nets.
dip net.
The size and shape of dip nets vary greatly. It is important to keep the following guidelines in
mind. Handle live fish using dip nets with relatively shallow bags. Their depth should not exceed 25
to 35 cm. One will have to select a size suitable for the size of fish to be handled.

I.5. TRAPS
There are many different kinds of traps commonly used when fishing in lakes and rivers in the
wild. It might be the case to catch broods-
tock or associated species as catfish.
Certain kinds may be useful for simple and
regular harvest of food fish without distur-
bing the rest of the pond stock.
These traps are usually made with
wood, plastic pipe, bamboo or wire
frames, with netting, bamboo slats or wire
mesh surfaces.
Opening: 25 to 30 cm
There are two main types (Figure 125 Length: 80 to 100 cm
opposite and Photo S, p. 136):
9 Pot traps, which are usually bai-
ted and have a funnel-shaped entrance
through which fish can enter but have dif-
ficulty escaping from; and
9 Bag or chamber traps, which
usually have a guide net that leads the fish
into a chamber and have a V-shaped en-
trance that keeps the fish from escaping. Figure 125. Differents types of local traps.


Photo S. Traps. On left and up on right,
traditionnal trap (Liberia); Down on
right, grid trap full of tilapia (Ehiopia)
[© Y. Fermon].

I.6. HANDLINE AND HOOKS
One of the easiest methods to capture broodstock is just with a fishing handline. It is a selective
gear which allow to capture and to maintain in life without problem fish like the tilapia.
It will however be a question of using as much as possible hooks without barb.

II. THE TRANSPORT OF LIVE FISH
Transport of live fish is common practice on many fish farms, used for example:
Ö After harvest of fish in wild;
Ö To take fish to short-term live storage.
The duration of transport varies according to the distance to be covered:
9 From the river, transport time is usually longer, varying from a few hours to one or two days;
9 On the farm, transport time is usually very short (a few minutes) to short (up to 30 minutes).
There exist certain basic principles governing the transport of alive fish:
Ö Live fish are generally transported in water. The quality of this water changes progressively du-
ring transport. Major changes occur in the concentration of the chemicals.
¾ Dissolved oxygen (DO) is mainly used by fish for their respiration. Bacterial activity and oxyda-
tion processes will also use oxygen in the presence of organic matter.
9 The oxygen consumption increase with the temperature.
9 The DO consumption by small fish for 1 kg is higher than fish a larger size.


9 The oxygen consumption of fish resting is lower than stressed or in activity fish.
¾ Ammonia is excreted by fish and produced by bacteria in different forms. The most toxic form,
free or non-ionized ammonia (NH3), becomes more important as water temperature and pH in-
crease.
¾ Carbon dioxide (CO2) is produced by fish as a by-product of respiration. Bacteria also produce
CO2 .Carbon dioxide exists in different forms; the most toxic form, free CO2, increases as water
pH decreases.

Other changes in water quality may also take place during transport.
9 Increased water temperature in warm climates increases oxygen consumption and the
content of toxic free ammonia.
9 Increased carbon dioxide content and thus decreased pH, reduce toxic free ammonia but
increase the content of toxic free CO2.
9 Increased suspended solids from fish waste.
Ö Water quality
¾ A cool water, so fish and bacteria will be less active, thus reducing DO consumption and produc-
tion of ammonia/carbon dioxide. Ice may be use if necessary. One will avoid to expose the fish
to a sudden change in temperature.
¾ A clear water which is free from silt or suspended solids, to reduce stress to the fish gills, to re-
duce bacteria in organic solids, and to reduce risk of low oxygen levels caused by decomposition
of organic material.

As far as possible, it is necessary to avoid handling fish with the hand too much because
its destroys the mucus which they have on the body and to leave them too a long time out of
water.
For transport itself, of short and medium time, one can use clay pots or barrels, buckets or ba-
sins but also plastic bags inflated with the air. For Clariidae, just a small amount of water is enough
because of their capacity to be able to breathe the ambient air.
In the case of long time transport, one will used plastic bags inflated with oxygen, with the air
if no oxygen (Figure 126 and Photo T, p. 138). One can get oxygen in a carriage-builder who makes
welding either in a dispensary or a hospital. As much as possible, each breeder will have to be alone
in his bag and, for the juveniles, one will limit the densities. However, it is true that this will increase
volume to be transported, thus, the risks of mortality are largely reduced. One should not put too
much water in the bag. A level just above fish is enough amply. One counts, in general, 1/3 of water
for 2/3 of air or oxygen.
For just catch fish, one will change the water of the container every 5 mn or when the fish pipe
on the surface, to evacuate the organic waste rejected by fish because of the stress of their capture
and which consume the oxygen of water and this, very quickly.
There exists a certain number of precautions to be taken and actions to be undertaken:
For transport in the medium and long term, before transport, when the fish come from the ponds,
one will keep them in stables, in hapas for example, without food and one will keep them long
enough so that their digestive tract is completely empty. Water in which they will be transported will
remain thus cleaner. The minimum duration of the period of fast depends on the temperature of water
and the species. In warm water, a duration from 12 to 12 midnight is sometimes sufficient. It is not
necessary for transport of short duration.
One will avoid, as much as possible, to dirty the water of transport. It will thus be necessary to
carefully clean the fish with clean water before loading them into the container with transport.
One will place the containers in the darkness and safe from sudden noises to maintain fish quiet
during the transport itself.
Wherever possible, one will maintain fish cool during transport. There will be transport during the


night or early in the morning. In the same way,
direct solar light will be avoided and it will be
preferably to place the containers in the shade.
The containers can bec over with bags or wet
tissue to increase the cooling effect of evapo-
ration
One should not feed fish during transport.
As much as possible, the water of trans-
port will be replaced by better oxygenated and
fresher water, during long stops, if the fish seem
disturbed or start to come to water surface to
breathe, instead of remaining calmly at the bot-
tom or when transport lasts more than 24 hours
without additional oxygen contribution. If ne-
cessary, the quantity of oxygen in water can be
increased by agitating water with the hand.
The density of fish should not be too high
to avoid a too strong oxygen uptake. For a bag
of ½ liter, 3 or 4 fish of 2 cm but only one of
8 cm must be put in. Moreover, for fish suba-
dultes and adults, wounds can be caused by the
contacts and may result in the death of a fish.
As soon as a fish died in a bag or a contai-
ner, it should be removed quickly.
For the release of fish in water, one will let
the container soak in order to reduce the va-
riation in temperature between the water of the
bag and the water of the pond. Then, one will
put water of the pond little by little in the contai-
ner to finish the acclimatization of fish before
releasing them.

Photo T. Fish packing in plastic bags
(Guinea, (Ehiopia)
[© Y. Fermon, © É. Bezault].
Regulator, valve
and air cylinder Deflate bag
and close it
Tie
around Pull
tube tube

Tube Air Air

Water Water + Water +
Water + air Water + air
Fish Fish
+ fish + fish
Figure 126. Fish packing in plastic bags.


III. THE PRODUCTION OF FINGERLINGS OF TILAPIA
It is possible to set up a production of fingerlings from broodstock collected in the wild. Indeed,
it is sometimes difficult to be able to provide fingerlings in good number in the wild, for example,
in rainy season. Three possibilities exist and vary according to the species. Fish can reproduce by:
Ö Natural, where one arranges a water level according to the behavioral needs and habitus of the
species to be breed and then put the breedeers,
Ö Semi-natural with injection of hormones to start the production of the gametes in a simulta-
neous way, and, finally,
Ö Artificial where, after injection, the ovocytes and sperm are extracted manually to proceed to a
manual fecundation.
The reproduction and the production of tilapia are currently carried out in farming systems ac-
cording to very variable levels of intensification, which depend on the topographic, physicochemical,
and socio-economic conditions of the area. The various techniques used until now are presented
according to the environment in which they are developed, namely:
9 Fish Ponds,
9 Hapas and cages,
9 Artificial tanks (basins), “raceways” and arenas,
9 Hapas in tanks,
9 Aquariums of experimentation.
In the situation of subsistence fishfarming, one will choose preferentially the production in
ponds and, if necessary, hapas and cages.
It is necessary to take account of the behavioral needs of the tilapia (Appendix 03 paragraph
II, p. 216). They are territorial animals. For the mouthbrooders, in fact, the males defend a territory. For
the substrate spawners, the two parents are territorial. Generally, one can consider that the size of
the territories will be about 1 m2 on the ground. This size will increase with the size of the individual.
However, individual variability is very important in these fish.
From their biology, fingerlings from 10 to 15 mm length can be obtain every month. Howe-
ver, for mouthbrooders, it will be necessary to take care of the females which suffer the harassment
of the males at the end of incubation. If they are requested too much, the guard of the fry will be
shorter with a greater risk of fry loss.

III.1. THE RECOGNITION OF THE SEx
It is sometimes rather difficult to differentiate the sexes from fish. In some species like Alestidae,
the sexual dimorphism appears on the anal fin. In many species of mouthbrooding Cichlidae, the
males present a bright coloration. However, some non-dominant males keep a coloring close to that
of the females. It is then necessary to look at the urogenital orifice while returning the fish (Figure
127, p. 140).
When the breeding season comes, broodstock should be carefully selected. Only fish that are
ready to spawn should be used. Select fish with the following characteristics:
9 Males should release a few drops of milt when the abdomen is slightly pressed.
9 Females should have a swollen and protruding genital opening, reddish/rose in colour, and
a well-rounded and soft abdomen, showing that the gonads are developed up to the dormant stage.
When there is risk of males agression (for example, in the case of catfishes), the fish of the two
sexes must be kept in separate ponds after selecting them.

III.2. THE NURSERY PONDS
In the case of a central processing unit making it possible to provide alevins to the whole of the
pisciculturists, one can propose with the local services the installation of a station of stocking with
fish in pond. In this case, one will choose ponds whose surface varies between 1 and 5 ares with a
depth from 0.4 to 0.5 m. Some authors recommend ponds of 4 ares, allowing a higher production, by
unit of area, with that of the ponds of 0.5 are. Others on the other hand recommend the use of small


Arrived at maturation

Milt drop

Anus

Urogenital A - Maturation test
papilla
Urogenital orifice Urinary orifice

Anus

Genital slit

B - Clarias gariepinus C - Lates niloticus

Papilla
Tail Head

Genital papilla

Anus
Oviduct
Urethra

D - Cichlidae Urogenital pore Anus

Figure 127. Sexual differentiation of differents species.


ponds from 9 to 12 m2 in which only one pair is introduced. The small size of these ponds facilitates
the regular fishing of the fry groups at the end of the parental guard. These small ponds do not re-
quire a monk. It is the latter system which will be privileged. This method, for mouthbrooders, allows
a production from 200 to 300 alevins per pair of parents and per month. It seems however that the
frequency of the spawns and the fry production are seriously improved while installing in these small
ponds 4 to 6 females with 2 to 3 males. That would in any case avoid the absence of production by
sterility of one or the other breeder. In pond of 4 ares, the stocking is made with 200 females (average
weight = 150 to 300 g) and 70 males (a.w. = 50 to 200 g), that is a density of 0.7 breeders/m2 and
a sex ratio female/male of 3:1 (Figure 128, Figure 129 and Table XXVIII below).
The reduction in the production of fry per kg of female, with the increase in the average weight
of the females can be attributed to 3 factors:
Ö Decreased fertility with increasing weight.
Ö Decrease in the frequency of eggs with increasing weight.
Ö Decrease in the frequency of reproduction of males towards large females more aggressive.
Regarding substrate spawners, the sex-ration must be reduced.
Two techniques of harvest are generally used, either the regular draining of the ponds at interval
of 60 days, in order to limit the frequency of the spawnings and separation of the breeders and the
fry using nets of adapted meshs size, or the harvest by seining or using cast net allowing to collect
all fingerlings of an average weight higher than 0.5 g. The exploitation begins 30 to 60 days after
introducing the breeders and goes on at the frequency of a harvest every 15 days.
From a biological point of view, one of the main advantages of obtaining fingerlings in pond is
the optimal use of the resources of the pond, compared with the mode of breeding in more closed
system. From a practical point of view, the breeding in pond is also of a simple technology, requi-
ring a less regular control than a breeding in artificial conditions. However, with high densities, the

Table XXVIII. Production of Oreochromis niloticus in function of the number of breeders in a
pond of 4 ares – 122 farming days.

Fingerlings production
Density breeders Sex ratio
(ind/m2) (female / male)
(ind/m /month)
2
(g/m2/month)

0.35 3 33.1 60
0.50 1 27.5 49
0.70 3 54.0 86
1.00 1 45.0 112
400

80
Nomber of fry/kg female/day
Fry production/m2/day

300
70

60

200 50

40

30
100
20
10

0 0
0 1 2 3 4 5 6 7 8 9 0 50 100 150 200 250 300 350 400 450 500 550
Genitors density (ind/m2) Females body weight (g)
Figure 128. Fingerlings produced per fish Figure 129. Fingerlings produced per females
density in Oreochromis niloticus. body weight in Oreochromis niloticus.


conditions of storage become more or less similar to those observed in cage or in tank and it is then
necessary to carry out a more precise follow-up of the various phases of production:
Ö Control reproduction of the breeders and frequent harvest of fry,
Ö Improvement of the productivity of the pond by fertilization,
Ö Regular fish feeding,
Ö Control of the water quality and renewal of water if necessary.

III.3. HAPAS AND CAGES
Under certain conditions, depending mainly on the mesh size and the density of the breeders,
the reproduction of the tilapia in cage is however realizable and has already led to very high produc-
tions of fry (Figure 130 below and Photo U, p. 143).
Hapas are fixed pocket of small size (de 1.5×1×1 m à 3×3×1 m) made with mosquito net (mesh
size of 1-3 mm) in nylon and attached to stick in bamboo, stakes or wooden stakes put into the bot-
tom of a pond depth. The hapa is placed at 10-20 cm from the bottom of the pond and the depth is
about 0.6 m. It can also be placed in a basin.
Thus, the breeders are confined in an internal room delimited by nets with mesh size of 30 mm,
so that the fry can be easily stayed in the external room (with 1-3 mm mesh size) as they are pro-
duced. This device presents the disadvantage of limiting the water flows through hapas, because
the breeders do not have access to the walls of the external room. However, it is known that the
movement of fish, like their action of algae and détritus scraping facilitate the water renewal within
hapas. An alternative is to put the breeders in a half of hapas, which allow to ensure the breeders of
good conditions of water circulation (Figure 131, p. 143).
The best results are obtained with densities from 2.5 to 5.0 breeders/m2. The best results are
obtained with sex ratio female/male of 5:1 to 7:1. Recently, however, of ratios 2:1 and 3:1 seems
more advantageous.

Internal
hapa

B

External
hapa

A2 A1

Figure 130. Hapas and cages. A: Hapas, A1: Simple, A2: Double; B: Cage.



A B C
Figure 131. Differents systems of reproduction of tilapia in hapas and cages. A: Simple;
B: Double with breeders in the middle; C: Breeders in one half.

One of the advantages of the use of the system hapas is the facility of control of the spawnings
and recovery of fry, each unit being easily handle by one or two people maximum. One can also get
the fry every day with hand net. A good harvest interval will be from 10 to 14 days for females of one
to two years old.
The cages generally consist of a rigid framework of wood made support or of metal equipped
with a synthetic net delimiting a volume of water and equipped with a system of floating attached to
the upper framework or supported by stakes inserted in the lakes or river at a shallow depth.

Photo U. Hapas in ponds (Ghana) [© É. Bezault].


The selection of the sites for the establishment of a breeding system in bcage is essential. Fac-
tors such as quality and circulation of water, adequate protection against the floating débris and the
waves, accessibility of the site, safety and distance compared to the markets are important to consi-
der. The brutal arrival of the first water of flood, extremely turbids, must also be taken into account,
because it involves a degradation of the conditions of farming and a stop of the feeding of fish. A co-
ver or a net of protection installed on the cage makes it possible to submerge it if necessary. Lastly, it
will be necessary to be attentive with the presence or the absence of water currents within the cage,
with the reduction in the concentration of dissolved O2 following the increase of toxic gases, and the
important thermal variations during the transitional periods.
Whatever the model used, the bottom of the cage must be at least at a distance of 0.3 m of the
bottom where waste accumulates and causes a reduction in the O2 concentration.
The cages for the reproduction and the fry production are generally smaller than those for the
production of fish for consumption, which is in cages of 0.5 and 1 m3. The depth of the cage can also
affect the growth and the reproduction of the tilapia. A depth from 0.5 to 1 m is generally observed
for the production of fish for consumption in cages of 20 m3. Meshs size of 3 mm seem to be a high
limit of size to observe the spawning of O. niloticus because the intermediate size of eggs is from
2.5 to 3.0 mms in diameter. The best production rate of fry (53 ind/m2/month) is obtained with a sex-
ratio of 3:1.
One will be able to feed the parents with rice, for example
As regards the production of fingerlings, the technique of breeding cages can increase very
significantly the amount of larvae produced through the frequent harvest larvae as their production.

A B

E

C D F
Figure 132. Live fish storage in hapas or nets. A: Wood frame and net bag;
B, C and D: Hapas or cage in net in pond or in channels; E: Basket;
F: Wood and mesh holding box.


These harvests, repeated and complete, are all the more effective as they do not require draining of
the pond, nor fishings with the seine, and thus limit the losses of offspring regularly observed at the
time of these operations. Moreover, the system with double net reduces the cannibalism exerted by
the adults, thus increasing the number of larvae produced by female. To note that cages and hapas
can be used to store fish collected during the draining of the ponds of production.
Consequently, in fishfarming production, it seems advisable to install parents with the
density of 4 ind/m2, of 1.5 to 2 years old, with males slightly larger than the females with a sex-
ratio of 1 male for 3 females.
These cages or hapas can be put directly in the water supply channe or other points where they
will be protected. They can be used for several ends:
Ö Production of fingerlings
Ö Storage of fingerlings collected in the wild
Ö Storage of the associated species after captures in the wild
Ö Storage of fish after draining of the ponds.
One will be able to also make use of small nets or others materials for that (Figure 132, p. 144).

III.4. THE OTHER STRUCTURES
There exist other structures like the concrete basins or aquariums to produce fingerlings. Howe-
ver, these structures are rather indicated for large production in commercial-type operations. They
require costs and technical much more higher and expensive (Photo V below).
The basins in masonry or breeze blocks generally have a elongated shape making it possible to
maintain a good circulation water.
The aquariums must be of big size (minimum 200 l for tilapia).

Photo V. Concrete basins and aquariums (Ghana) [© Y. Fermon].


IV. THE STOCKING OF THE PONDS
When the pond is filled with water, that it will have been fertilized and that water will have be-
come sufficiently green and that the fingerlings are available, it is now time to introduce them into
the ponds.
The density of fish, in relation to the species and its behavior is one of the key components of the
success of the farming. Then, when the herbivorous fish arrive at a size enabling them to reproduce,
one will put some predators to control the reproduction and to limit to possible the presence of a too
high number of fry. The fish will not do what you want that they make. They will evolve accor-
ding to the conditions that you give them. It thus will be necessary to give them optimal conditions
for an investment of their metabolic energy in the growth.
The optimal density of stocking of a fishpond is the amount of fish at the beginning of the pe-
riod of production which guarantees to obtain the highest income. The definition of the density of
stocking of a pond is one of the most important parameters for the success of a fishfarming. In the
fishfarming systems, a stock of fingerlings grows bigger at an almost maximum speed as long as
the food and the other environmental conditions are not limiting. When they become it, the reached
biomass is called critical charge (CSC). The growth decreases starting from this CSC, but it is not
null. The biomass thus continues to increase, until the population reaches the level of biotic capacity
or (K). Starting from K, the effects related to the density of the population are such as the growth stop
and the biomass remains stable. It is however possible to increase the density of stocking, which
makes it possible to increase the yield, as long as the rate of increase in the density of stocking re-
mains higher than the reduction in individual growth rate. But, from the moment when the reduction
in growth rate becomes higher than the increase in density, the yield falls, as that appears on Figure
133 below.
If the fish are put in ponds with low density and that the natural foods are abundant, they grow
bigger with the maximum speed allowed by the temperature. A supplementary feeding contribution
is useless at this stage and does not bring anything more because the food is not a limiting factor. On
the other hand, when high stock
reaches the CSC, the food be-
comes limiting. The growth thus
decreases, except if the manage-
ment of the farming is intensified.
If the production of natural food
can be increased by fertilization,
Y the maximum growth is started
Yield per unit area (Y)

again, until a new CSC is reached
Growth rate (G)

on a higher level. At this stage, a
complementary food can be ne-
cessary to the maintenance of the
G maximum growth. Then, again, a
G
CSC is reached when the quality
of food or water quality becomes
limiting.
Y The density can be used to
control the average growth rate
of fish and consequently, the du-
ration of the period of farming.
Density of fish
As already considering, when the
density of stocking is increased,
the CSC is reached for a less in-
Figure 133. Diagram on the relationships between the dividual weight and the growth
stocking density, the instant growth rate (G) and the beyond the CSC is reduced. The
instant yield per surface unit (Y) with (dots) and without average growth on the totality of
(plain) complementary feeding. the period of farming is conse-


quently lower. In a more general way, the individual yield and the growth are respectively positively
and conversely correlated with the density. In other words, until a certain threshold, more the density
is low, more the growth is fast and more the yield is low.
The fishfarming systems in pond selected are polyculture dominated by the tilapia, especially
Oreochromis niloticus (or others tilapia). In some places, a catfish was selected like principal species.
The group of catfish with Clarias gariepinus, Heterobranchus isopterus and Heterobranchus longifilis
is the second great group, the last of these species (H. longifilis) is used only in intensive systems of
farming with granulated food. Although very often forgotten, Heterotis niloticus is probably the third
fish by order of importance.
By using relatively low densities, a better growth rate, a higher final weight but a lower yield can
obtained. But with a higher growth rate, the duration of the cycle of farming decreases, which can
allow to obtain a higher benefit at the end of the year. Experiments led in Ivory Coast showed that
the compromise between the yield and the final average weight is for a density ranging between
4 000 and 7 000 tilapia/ha (Figure 134 below). From now, it is advisable to use a densities of stocking
lower than before for the fishfarming of low level of inputs. This density is of 5 000 poissons/ha, that
is 0.5 ind/m2. Before, the usual density was generally of 2 ind/m2.

Ö The density of tilapia have to be of 0.5 ind/m2.

The majority of the projects retained and still retain the catfish (often Clarias gariepinus). This
technique is very constraining: It is necessary to be able to get, at each beginning of cycle, catfish
fry well calibrated to prevent that those do not attack the tilapia in growth in the pond. Moreover, if,
for an unspecified reason, the duration of the cycle increase, the catfish, growing faster, will forsake
fry of tilapia to attack the large individuals. The value of the production fall down then since the large
fish are more expensive than the small ones. If some seasons, the catfish fry are aboundant, they
are difficult to find in the wild at other times of the year. In the extensive fields, Clarias gariepinus
appeared a poor carnivore, incompetent of reduce the amount of fingerlings. On the other hand,
some individuals have a growth so fast that they are able to attack the large tilapia at the end of 4 to 5
months. It is to better retain Hemichromis fasciatus, or another piscivorous Cichlidae with an easiest
management. This small carnivore, of size definitely lower than the tilapia, can attack only fry. It is
with this type of carnivore that the fastest growths of the tilapia were recorded (Figure 135, p. 148). This
gives a new advantage: It makes it possible to quickly obtain a product of large size, appreciated
better by the consumer. The eradica-
6000 600
tion of fry of tilapia (first competitors
for the large tilapia for the food re-
5000 500 source) allow to develop twice better
Mean weight (g)

the inputs. Moreover, the presence of
4000 400 carnivores facilitates the control of
the populations. It is not then neces-
Yield (kg/ha/year)

sary any more to practice tiresome
3000 300 and hazardous fishing to eliminate
fry. This does not prevent, once the
2000 200 field controlled by a predator, to ju-
diciously use some catfish put after
the beginning of the cycle, and with a
1000 10
density where they will not influence
the growth of the tilapia.
0 0 The polyculture with Heterotis ni-
0.1 0.4 0.7 1
loticus became important at the end
Density (ind/m2) of 80s. This species does not seem
Figure 134. Yield and average weight of Oreochromis to induce a reduction in the yield of
niloticus at the harvest in function of initial density. the tilapia, but appears, at contrary,


perfectly complementary. One leaves a number very limited breeders of Heterotis (of more than 1
year and half old) to reproduce, one observes the way in which the reproductive breeders take care
of its fry and, when those appear sufficiently large to be isolated, they are collected (at the end of
1 to 2 months). In economic terms, the association of Heterotis and tilapia corresponds to a more
intensive use of surface.
The polyculture with of Cyprinidae is still weak in Africa except with introduced species. One can
think that this one can develop with indigenous species.
One can thus associate the tilapia as principal species (Oreochromis niloticus when it is present)
with a catfish (Heterobranchus isopterus, Clarias spp.), Heterotis niloticus and a predator (Hemichro-
mis fasciatus, Parachanna spp. or Serranochromis spp.) to eliminate undesirable fry, according to a
ratio of 0.03 for Heterotis niloticus, 0.04 for Siluriformes, 0.2 piscivorous for each tilapia.

For the predator, the proportion must be approximately 13% of the weight of put tilapia.
Globally, ten fish of approximately 7/8 cm for a hundred tilapia having reached 6/7 cm are
enough. The stocking of predators will be done approximately one month after stocking the
pond in tilapia.

Introduction of predator
Reproduction
at small size


Growth

 
Growth
Available food  Reproduction
Available
at higher size
food


Growth

Predation
Reproduction
at small size

Dwarfism Good growth

Figure 135. Impact of the presence of a predator (here, Hemichromis fasciatus) in fishponds.
On left: Without predator; On right: With predator.


V. THE FOLLOW-UP OF FISH
For proper management, you will need to know on regular occasions how big your fish are and
how fast they are growing. For this, a sample of fish from the pond will be measured and weighted.
For live fish it is always best to weigh them in clean water, as quickly as possible (Figure 136
below).
The total weight of a certain number of fish can be measured. Best is to put a batch in a container
or a bag which will be weighed. After counting of fish, there will be then a mean weight by individual.
To measure the live weight of relatively large fish such as breeders, one can simply use a satchel
or stretcher made for example of canvas slung from two wooden bars.
Length measurements are particularly quick and useful for medium to large fish and can be done
with far less stress or damage to the fish. The easiest way to measure fish length is to use a fish
measuring board. You can make one simply of wood. One fixes a flat ruler graduated in millimetres
and centimetres on top of the horizontal board. One also fixes a small plank perpendicularly against
which one will bring the rule to thfe level from the zero. One make sure that the board is smooth. A
coat of good waterproof varnish is useful.
To measure the length of a fish, one places it on the horizontal board, the end of his head against
the small vertical plank, therefore on the level zero of the rule. His caudal fin well is extended and
one measures the length on the graduated scale. One often uses the total length or the fork length.
However, it is better to use the Standard Length (SL) (Appendix 03, paragraph I, p. 207).

Tare Weighing

Spring

B
A simple wooden
fish measuring box
finish with water
proof varnish

Commercial

A
Figure 136. Measurement gears. Ruler in mm or cm
A: Balances and springs; B: Taking a weight;
C: Measuring board. C


240

220

200

180
Fresh weight (g)

160
146
140

120

100

80

60

40

20

0
0 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
20.4
Total length (cm)

Figure 137. Length - Weight relationships.

Length and weight of fish can be related mathematically, and so weight can be estimated from
length measurements (Figure 137 above). This relationship varies with the species and its environ-
ment. For that, it is necessary:
1. To take a fish sample in the pond.
2. To measure the standard length preferably each individual then,
3. To weigh fish individually.
The sample must have a minimal size of 20 individuals, even if statistically a sample of 5 indi-
viduals is enough.
If the weighing of fish is difficult, it is advisable to use the relation length-weight, in order to
consider the individual mean weight of fish. It is enough for this purpose proceeding as follows.
To make a follow-up of growth, one will proceed as follows (Appendix 01, p. 189):
1. To take measurements of a fish sample during stocking;
2. For fish of less than 5 cm of LS, there will be twice a week the same manipulation during the first
month. Then, the catches of measurements will be able to be spaced, one per week.
It is well, as much as possible, to follow the growth over one 3 months duration.

VI. DRAINING AND HARVEST
Farmed fish can be harvested in several ways. One can collect all fish only once (complete drai-
ning) or one can do it in several times by making intermediate fishings without emptying the pond
before draining completely.

VI.1. INTERMEDIATE FISHINGS
This method allows the owner to get fish throughout farming. It can do it with a net, a cast net,
traps or handlines. At the same time it can follow the growth of fish. Intermediate fishings should
however not be done too early, it should be waited until the fish reached a sufficient size before col-
lecting them for consumption. The size of fish to harvest varies according to the place where is the
location. Sometimes, the fish are consumed with size lower than 10 cm SL.
For each harvest, it is necessary to remove only a small amount of fish, especially if there is many
intermediate fishings. The owner will have each time to note the weight of the fish which it catchs


from the pond, in order to add them with the production at the time of complete draining. If these
fishings are made in a moderated way, they make it possible to collect a total production higher than
if one practices only one draining at the end of the cycle. To collect fish, one will be able to use fishing
gears (Chapter 09, paragraph I, p. 127).

VI.2. COMPLETE DRAINING
A draining is done always early in the morning, in order to be able to work during the hours of
freshness. Thus the fish and especially the fry which one will keep will suffer less. The material and
necessary tools for draining (shovel, basins, baskets…) will be gathered the evening before. One will
be able to store fish not consumed or sold in cages or hapas. The sale of fish will be envisaged either
at the edge of the pond and, in this case, one will inform the neighbors, or at the market of the village,
so a fast way of transport will then be provided.
When the pond is equipped with a monk, collect fish can be done in two manners (Figure 138
below):
Ö Inside the pond, just in front of the monk;
Ö Outside the pond, after the fish crossed the monk and the pipe discharge.
To harvest your fish inside the pond, one will remove the wooden boards from the monk one row
at a time. Each time a row is removed of boards from the monk, one will be sure to put the screen
back on top to keep the fish from getting out.
When the water is partly drained from the pond, one can harvest part of the fish from the water
just in front of the monk. (Figure 139, p. 152). When one will be ready to harvest the rest of the fish, one
will continue to take out the boards one by one. However, it is necessary to put back the screen each
time until the pond is empty. When all of the water is out, the remaining fis can be harvested. First the
baby fish have to be collected and then the big fish. Muddy water is bad for baby fish. So, it is better
to let a little clean water flow through the pond to keep it from getting too muddy.
A number of fish will pass through the monk. One can place a box or baskets in the draining
channel outside the pond, at the end of the pipe coming from the monk (Figure 197 below). It will be
necessary well to pay attention that the pipe is well inside the box, so that the fish cannot escape.
So now we proceeded to harvest fish.

A

B

Figure 138. Harvest of the fish. A: Inside after
complete draining; B: Outside, with a box;
C: Inside, at the catch basin.
C


m Basket
0 c
50 20
cm
50 cm

20
cm Netting

Harvesting box
Figure 139. Examples of way to collect the fish outside of the pond.

VII. SUMMARY

Ö After fertilization, the steps are:
Ö The collect of specimens in the wild or by production of fingerlings of tilapia;
Ö The stocking of ponds with tilapia;
Ö The growth monitoring;
Ö The collect of predators in the wild;
Ö The stocking with predators;
Ö The monitoring and partial harvest of fish;
Ö Then, after several weeks, the draining and the complete harvest of fish.
Ö Emphasis on:
Ö Fishing methods and precautions to keep fish in good condition and avoid pro-
blems and local legislation;
Ö The biology of the species and they provide for good production, breeding, fee-
ding, behavior, both for good growth and in the choice of density;
Ö The transport of fish and to provide care in order to avoid a loss of fish which may
be the complete number of fish.


Chapter 10
MAINTENANCE AND MANAGEMENT OF THE PONDS
As soon the fish are harvested, the cycle is thus ended (Figure 140, p. 154). It remains, however,
to see various aspects to ensure a durability of the ponds and, thus, other productions. They are
related to:
9 The maintenance of the ponds;
9 The techniques of conservation and transformation of fish;
9 The management of the ponds;
9 The ponds and health.

I. THE MAINTENANCE OF THE PONDS
In order to be able to have a correct production and this over several years, it is advisable to
ensure a certain number of interventions and to take precautions on various aspects:
¾ The diseases of fish,
¾ The nutrition of fish,
¾ The regular maintenance of the ponds,
¾ The maintenance of the ponds between two uses.

I.1. THE DISEASES OF FISH
Fish diseases may cause severe losses on fish farms through:
Ö Reduced fish growth and production;
Ö Increased vulnerability to predation;
Ö Increased susceptibility to low water quality;
Ö Increase of death of fish.
While it may be difficult to avoid fish diseases completely, it is better to try to prevent their occur-
rence rather than to allow them to develop and then attempting to cure them once they start to cause
problems In some cases surviving fish are so weakened that effective treatment becomes difficult.
However several simple and effective treatments can be used, either for prevention or early
control of disease before it becomes too serious.
There are several causes of disease that may affect the fish directly or may continue to cause
disease problems. Basically, any factor which causes stress or difficulty to the fish decreases its
resistance to disease and increases the chance of disease problems occurring.
The three main causes of disease are:
Ö An inadequat feeding. Nutritional diseases become more frequent as the culture system be-
comes more intensive and the fish obtain less of their nutrients from natural food organisms.
Ö A stress cause by being exposed to an extreme or a toxic condition.
¾Rough and/or excessive handling, for example when harvesting or sorting/grading;
¾Overcrowding and/or behavioural stresses, for example in storage or transport;
¾Unsuitable water temperature;
¾Lack of dissolved oxygen;
¾Changes in pH towards extreme values;
¾Presence of toxic gases such as ammonia or hydrogen sulphide;
¾Pollution of the water by agricultural or industrial chemicals, sewage effluents, heavy silt loads.


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining

Figure 140. Setting of fish pond: 5. End of cycle and start again…


5. END OF THE CYCLE 3. PONDS, 4. FISH FARMING
Ö An attack of pathogenic organisms, either externally on the skin, gills or fins, or internally in the
blood, digestive tract, nervous system…
Disease risks become even greater when fish undergo combined stresses, for example handling
when the water temperature is below normal or overcrowding in low dissolved oxygen conditions.
Other factors on the fish farm may also be responsible for the survival and propagation of di-
sease organisms, making disease control much more difficult such as:
9 The presence of diseased wild fish;
9 The presence of intermediate hosts such as snails and fish-eating birds, necessary for com-
pleting the life cycle of the disease organism;
9 The introduction of disease organisms through contaminated inputs such as food, trash
fish or processing wastes, for example imported eggs, juveniles, or broodstock, and water from an
upstream pond or farm.
Disease prevention can be done with just applying good management practices:
Ö Ensure good water quality: sufficient supply, with adequate dissolved oxygen concentra-
tion and free of pollution.
Ö Keep the pond environment healthy: control silt, control plants, keep a healthy balance of
phytoplankton and zooplankton, and exchange water if needed.
Ö Keep the fish in good condition with control stocking density. Keep different sizes or sexes
separate if necessary to control fighting. Care for your fish during storage and transport.
Ö Prevent the entry of disease organisms from outside your farm.
Ö Prevent the spread of disease organisms within your farm. If a disease breaks out on the farm,
remove dead or dying fish from the ponds as quickly as possible, at least daily, and do not disturb
and stress remaining fish excessively.
Apart from obvious signs such as dead or dying fish, there are many other symptoms which
show that fish are not healthy (Figure 141, p. 156):
9 The behaviour of your fish becomes unusual:
¾ Swimming weak, lazy, erratic,
¾ Floating in water head up,
¾ Rubbing against hard object,
¾ Flashing and twisting,
¾ Darting repeatedly,
¾ Crowding and gathering in shallow water or at water inflow,
¾ Individual fish isolated from the main group of fish.
9 Some physical signs are present on the fish:
¾ Gaping mouth,
¾ Body: Open sores, leions, bloody areas, loss of scales, bloated belly, abnormal coloration,
¾ Gills: pale, eroded, swollen, bloody or brownish,
¾ Eyes: cloudy or distended,
¾ Fins: folded,eroded,
¾ Presence of disease organisms on skill, gills, fins.
It is not easy to identify in a fish pond why fish show signs of bad health. There are two common
situations which you should readily recognize:
Ö A large part (if not all) of the fish stock show distress or die suddenly, with only some of the above
symptoms of disease such as gasping at the surface or gaping mouths: the cause is prior stress (for
example rough or poor handling or transport) and/or bad water quality (often low dissolved oxygen)
or the presence of a toxic material such as pesticides or other pollution.
Ö Only a few fish are dead while some others show distress. Usually a few fish die over a period of
several weeks and some of the above symptoms are present. The cause is improper feeding and/or
development of some disease organism.


A B
Figure 141. A: Fish piping on surface; B: Dead fish floating on surface.

Most treatments required not easily findable chemicals and which can pose problems of
handling and toxicity. One will thus avoid employing any treatment. It will then be advisable to
sacrifice sick fish. However, it will be advisable to know if one deals with disease related to
pathogenic organisms.
When that is possible and if that appears to be essential because of the importance of diseases
in a zone, one can carry out an autopsy with, in particular:
1. Search for external parasites;
2. Search for internal parasites;
3. Color and aspect of the liver.
There are three major groups of living organisms that may be responsible for fish diseases: (Fi-
gure 142 below and Figure 143, p. 157):
9 The viruses. Their detection and identification requires highly specialized laboratory tech-
niques. Control of viral diseases is difficult and requires specialized advice.
9 The bacteria. Bacteria are minute single-cell organisms (I to 12 µm), usually living in colonies.
Their detection and identification generally also require special laboratory techniques. The treatment
of bacterial diseases such as tail or fin rot and skin ulcers requires experienced, specialized advice.
9 The parasites. Parasites are very small to small organisms made up of one or several cells.
They develop either inside or outside the body.

Ichthyophthirius
(Protozoa)
Skin ulcers

Leeches
(on body)

Tail rot
Lernaea
(Copepods)
Dactylogirus
(on gill)

Gill rot Bacteria Saprolegnia
(1 à 12 µm) (Fungi)
A B
Figure 142. Diseases of fish. A: Bacterial diseases; B: External parasites.


Infected fish White
spots

Juveniles free-swimming Maturing trophozoïte in skin and
in water (tomites: 30 to gills (2 days at 25-28°C)
40 µm)
Life cycle from 3 to 5 days at 20°C

This disease may spread rapidly from one
fish to another through water and pond Mature trophozoïte
bottom infections which makes disease free-swimming in
water (500 to 1000 µm)
control very difficult

Juveniles
escape from Parasite encysts on pond
the cyst bottom and sbdivides into
many juveniles
A

Adult trematode:
In gut of water • Internal fish parasites are very difficult to
bird
control. Although their effects can sometimes be
easily identified, detection and identification of
Metacercariae the parasites themselves usually requires special
in fish eyes
skills.,
• External fish parasites are much easier to
Egg in detect and identify. It is usually possible to eli-
water
minate them.
Š Protozoa are very small, single-cell parasites,
Š Flukes (Monogenea) are very small worms atta-
Miracidium ched by hooks (0.3 to 1 mm),
Š Leeches are rather large, segmented worms
attached by a sucker on each end (3 to 5 cm),
Cercariae in Š Copepods (crustaceans) attached on the fish
water
body with often two elongated egg sacs atta-
Snail as
B ched,
intermediate host
Š Fish lice (Crustacea) have a flat, disc-like body
covered by a rounded dorsal carapace (6 to
Figure 143. Example of life cycles of fish 10 mm),
disease factors. Š Water fungi (water moulds) are made of fila-
A: Ichthyophthirius multifilis – White-spot ments that usually grow into a cotton-like mass
diseases; or mat. They can also develop in the gills.
B: Diplostomum spathaceum - Diplostomosis.


I.2. THE FEEDING OF THE FISH
In will the majority of the cases, the fish will take most of their food of the small animals and
plants which grow in green water (Chapter 08 p. 118).
However, it will happen that it is necessary to distribute additional food contributions if the pri-
mary production in the ponds is not good and, therefore, if the growth of fish is low.
From a point of view of the nutrition, the organic matter includes the protids (proteins), the lipids
(fats), the glucids (carbohydrates), as well as substances in proportion relatively low (micronutri-
ments) such as the vitamins and minerals.
The requirements in nutrients vary according to the species (Table XXIX below).
The diet varies according to species (Appendix 03 p. 207).
Many kinds of materials may be used as supplementary feeds for your fish such as:
9 Terrestrial plants: grasses, legumes, leaves and seeds of leguminous shrubs and trees, fruits,
vegetables;
9 Aquatic plants: water hyacinth, water lettuce, duckweed;
9 Small terrestrial animals: earthworms, termites, snails;
9 Aquatic animals: worms, tadpoles, frogs, trash fish;
9 Rice: broken, polishings, bran, hulls;
9 Wheat: middlings, bran;
9 Maize: gluten feed, gluten meal;
9 Oil/cakes after extraction of oil from seeds of mustard, coconut, groundnut, African palm,
cotton, sunflower, soybean;
9 Sugar cane: molasses, filter-press cake, bagasses;
9 Coffee pulp;
9 Cottonseeds;
9 Brewery wastes and yeast;
9 Kitchen wastes;
9 Slaughterhouse wastes: offals, blood, rumen contents;
9 Silkworm pupae;
9 Manure: chicken droppings, pig manure.

Table XXIX. Levels of various nutrients in different species of fish.
Percentage per size class of fish
Nutrients < 0.5 g 0.5 to 10 g 10 to 35 g > 35 g Breeders
Tilapia
Crude proteins 50 35 - 40 30 - 35 25 - 30 30
Crude lipids 10 10 6 - 10 6 8
Digestible glucids 25 25 25 25 25
Fibers 8 8 8 - 10 8 - 10 8 - 10
Catfish
Digestible proteins > 27 27 29 22 - 24
Common carp
Digestible proteins 27 31


If one chooses the use of additional feeding, the products showing the following characteristics
will be preferentially selected (Table XXX below):
Ö Adequate food value: high percentage of proteins and carbohydrates and low content of fibers;
Ö Good acceptance by the fish for which they are intended;
Ö Economic reasons: for a given quality, to choose least low cost preferably;
Ö Food available during most of the period of growth of fish;
Ö Minimal additional costs of transport, handling and treatment;
Ö Facility of handling and storage.

Table XXX. Relative value of major feedstuffs as supplementary feed for fish.
Content
Feedstuff Water Crude proteins Carbohydrates Fibers
Cereals
Rice broken 11.3 L VH VL
pollshing 10.0 L VH L
bran 10.0 L VH H
hulls/husk 9.4 VL H VH
Wheat bran 12.1 H VH L
middlings/pollard 10.5 H VH L
Oilcakes
Coconut/copra 8.5 H VH H
Cotton seed without hulls 7.8 VH H H
complete 7.9 H H VH
Groundnut/peanuts without hulls 10.0 VH H VH
Mustard 9.5 VH H L
Palm 10.5 H VH H
Sesame 8.0 VH H L
Soybean with hulls 11.0 VH H L
Sunflower with hulls 7.3 VH H VH
Other terrestrial vegetables
Coffee pulp fresh 11.4 L VH VH
Lucerne, leaves 76.0 VL L L
Sweet potato, leaves 89.2 VL VL VL
Sugar cane fresh bagasse 45.0 VL H VH
molasses 25.0 VL VH nil
Aquatic plants
Water jacinth (Eichornia crassipes) 91.5 VL VL VL
Kangkong (Ipomea aquatica) 92.5 VL VL VL
Water lettuce (Pistia spp.) 93.6 VL VL VL
Animal by-products
Blood cattle, fresh 79.6 H nil nil
Ruman contents, fresh 57.5 VL H H
Very high = VH 30 - 42 40 - 55 20 - 30
Intervalle de valeurs High - H 16 - 21 20 - 30 12 - 15
en pourcentage du
poids Low = L 7 - 13 7 - 10 5 - 10
Very low = VL <5 <5 <2


Table XXXI. Example of formula for tilapia and catfish farming.
Tilapia / Catfish in Tilapia / Silure in non
Feedstuffs Catfish fry (< 5 g)
fertilized pond fertilized pond
Fish flour 5 20 55
Soy flour 15 10 7
Cottoon oilcake 25 10 7
Brewery wastes 15 10 7
Bran rice 20 15 5
Wheat 10 10 -
Cocoa or coffee 10 10 -
Maize flour - 10 5
Calcined bones flour - 5 4
Palm oil 5
Composition (%)
Crude proteins 28.5 29.5 43.3
Crude lipids 8.0 9.0 11.0

To obtain best results, it is better to use simple mixtures of various feedstuffs to provide the fish
with the additional proteins and good carbohydrates required. As far as possible, one will have to
avoid using a high proportion of fibrous materials to feed the fish. (Table XXXI above). The mix will be
made regarding the available feedstuffs for a lowest cost.
It is not easy to know which quantity exactly of food to give to fish. The observation of fish allows
to have an idea of their needs.

To determine the necessary quantities the following factors have to be take into account:
Ö The small fish relatively need more food than the large ones.
Ö In the presence of an abundant natural food, less additional food is necessary.
Ö The quantity necessary of additional food is of as much less important than its quality is impro-
ved,
Ö Water with high temperature requires a more abundant feeding than water at fresher tempera-
ture.
The total quantity of sup-
Table XXXIII. Feeding rate for tilapia in pond related
plementary feeding to be given
to the size (table of Marek).
daily to the fish in a particular
pond is usually expressed as a Size class Rate in monoculture Rate in polyculture
percentage of the total weight 5 to 10 g 6.67 5.33

Table XXXII. Example of 10 to 20 g 5.33 4.00
quantity of food to give ac- 20 to 50 g 4.60 3.71
cording time per m2 of pond. 50 to 70 g 3.33 2.67
Time Weight / m2 70 to 100 g 2.82 2.24
1 360 100 to 150 g 2.16 1.76
2 480 150 to 200 g 1.71 1.43
3 720 200 to 300 g 1.48 1.20
4 960 300 to 400 g 1.29 1.03
5 1200 400 to 500 g 1.15 0.93
6 1440 500 to 600 g 1.09 0.87


or biomass (B), of fish present. This percentage is called the daily feeding rate (DFR). For example, if
DFR = 2.5 % of the fish biomass B = 80 kg, it will require 80 x (2.5 / 100) = 2.0 kg of supplementary
feed to be distributed daily in the pond. This quantity will change during the growth of fish and thus
of the increase in the biomass of fish in the pond (Table XXXII and Table XXXIII, p. 160).
If the fish do not eat all distributed food, it is advisable to decrease a little the quantities the
next day. Conversely, if the fish quickly eat all distributed food, a little the quantities will have to be
increased the next day.
To be able well to observe fish, it is easier to feed them at the same time each day, preferably ear-
ly the morning and in end of the afternoon, when the weather is fresher and this, at the same place.
It is easier to feed them in the lower deep part of the pond in order to be able to observe them
while they eat. If the quantity of distributed food is too important, part of this one will settle at the
bottom of the pond, which will pollute the water of the pond.
To facilitate the feeding and the observation, one can manufacture a square or a circle frame of
bamboo or light wood and attach it to a stake that to insert in the ground. It is then enough to put
the food inside the square or of the circle (Figure 144 below). One will be able better to thus see
the quantity of food which settles at the bottom or to touch the bottom with the hand to see food
whether settled.
There are several occasions on which it is advantageous or even compulsory to stop feeding
your fish:
9 When the water temperature is too low or too high (Table XXXIV below);
9 When dissolved oxygen content is limited;
9 On the day you apply manure to the pond;
9 If ever a disease epidemic appears in the pond;
9 When manipulations have to be done in the pond.
It will also be necessary to pay attention to storage in the event of need for feeding. Feedstuffs
must be stored with special care to prevent excessive deterioration in quality and feed losses. The
most Important factors to control are the following:
9 Moisture content of both air and feedstuffs should be maintained as low as possible.
9 Temperature of both air and feedstuffs should be kept as low as possible. At temperatures
above 25ºC, the rates of deterioration and loss may rapidly increase.
9 Moulds (fungi) and insects (beetles, moths, weevils, etc.) may cause considerable losses
and may contaminate feeds with their metabolic by-products. High temperature and high moisture
levels favour their development.
9 Rodents (mice, rats, etc.) and birds
Table XXXIV. Examples of stop feeding per species can consume important quantities of
in function of the temperature feedstuffs. Their wastes may also conta-
Species Range of stop temperature
minate the feeds.
9 Human theft and indirect damage
Mosambic tilapia < 19 and > 35°C
to feed stores may also increase other
Nil tilapia < 18 and 34°C
control problems.
Catfish < 18 and 36°C

Earth mound

A B C
Figure 144. Structures to facilitate the feeding. A: Raised pond area;
B: Fixed submerged tray; C: Fixed floating frames.


I.3. DAILY ACTIVITIES OF FOLLOW-UP
Although reduced in a case of production fishfarming, certain regular activities must be carried
out to ensure a good production of fish (Table XXXV below).
At least once per day, the fishfarmer must visit the ponds and check that:
Ö The water supply entering each pond is adequate;
Ö The dikes are in good state;
Ö Water quality is satisfactory, as shown by the behavior to fish and the presence of plankton.

The best moment of the day for this visit is early the morning, when the dissolved oxygen
contents are likely to become insufficient and that the owner can contribute to preserve the good
state of health of fish. If possible, a second visit of the ponds can take place towards the end of the
afternoon, in particular during the critical periods, to take care that the fish remain in good health
during the night.

More detailed controls must be made once per week and in a periodic way on:
Ö Channels and dikes of the ponds, for major maintenance or repair,
Ö Filters,
Ö Compost piles, in order to fill them if necessary.

In all circumstances, it is necessary to maintain under control the development of the terrestrial
vegetation and to use it for composting.
It will also have to be taken care that the ponds remain protected well as that was mentioned
before (Chapter 07 p. 73).

Table XXXV. Monitoring. x: following; xx: fuller check or major repair; V: In drained pond only.
Items Monitoring and possible action Daily Weekly Periodically
Water supply
Main water intake Clean/repair/adjust x - -
Water supply channel Clean/repair/adjust x xx -
Pond inlet Clean/repair/adjust x - xx V
Filters Check/clean x - x
Pond
Water level Check/adjust x - -
Water quality Color check x - -
Dikes Check/repair/protect x xx xx V
Bottom mud Thickness check/quality - - xV
Aquatic plants Check/remove - x xx V
Terrestrial plants Check/remove - x xx
Pests Check/remove x - xx
Fish
Fish behavior Check x - -
Compost piles Check/refill - x -
Theft Protect x - -


I.4. MAINTENANCE WORK AFTER DRAINING
I.4.1. DRYING POND
The drying of a pond is the time that a pond stay without water (period between draining and
next water filling). It can be total or partial, for short to long time.
The dry setting allow some favorable effects because physicochemical and biological pheno-
mena:
Ö Mobilization of nutrients in the soil,
Ö Rapid mineralization of organic debris,
Ö Destruction of aquatic plants, germs of disease, parasites and predators of some fish.
The period of dry setting can be reduced at a few days. A short period is also preferable to avoid
the formation of cracks in the dikes and in the bottom of the pond, due to the shrinkage of clays. A
light work of the surface bottom of the pond can contribute with the ventilation of the ground and the
three points mentioned above. However one should not plow deeply, because that could cause an
increase on the unproductive land surface, and an in-depth hiding of the surface layer rich in nutritive
elements. A culture (leguminous plants or food crop) can be carried out on the bottom of the pond
during a prolonged dry setting. The not collected parts will be then put into the ground before the
filling again the pond in water. However, this culture will have to be as short as possible.
I.4.2. CLEARING THE PLATE
It is generally at the deepest place of the pond (in front of the monk), that the mud tends to accu-
mulate. It is necessary to remove it so that the fish can, during harvest, havethere the water cleanest
possible. This mud is composed of an accumulation of sediments of the surface layer of the bottom
of the pond and organic remains. It is thus very rich in nutritive elements and can be used beside the
pond as fertilizer for gardenings. It is also possible, in order not to lose these nutritive elements, to
distribute this mud on other places of the plate without however leaving too much of it.
I.4.3. REPAIR OF THE DRAINS
The drains tend to be filled during the productions. A fast passage according to the layout of the
initial network will be enough, but mud will have to be rejected far and not deposited on the edges
of these drains.
I.4.4. REPAIR OF THE DIKES
At the time of the construction of the ponds a slope inside the pond was respected. During the
production a degradation occurs because of the digging of the banks by the population (nests of the
tilapia), collapses by compressing during carried out work, a ceaseless erosion due to the waves (in
the large ponds). It is then necessary to carry out a banking up of the dikes by contribution of new
ground (clay) and to remake the initial slope. If necessary, it will be necessary to stop the burrows
dug by small animals in the dikes.
I.4.5. REPAIR OF TH E WATER INLET
It often happens that the water inlet was badly envisaged (too short) and that a digging occurs
in the dike upstream of the pond plumb with the pipe. A flat rock stone or pile is deposited on the
bottom of the pond at the point of fall of the filament of water to break the jet and to reduce degra-
dations by undermining. If not, a repair of the dike is essential with a stone facing to limit the erosion
of water..
I.4.6. MAINTENANCE OF THE MONK
When there is monks of brick or masonry, it is necessary to check the external rough coat. If
a light deterioration is noted, the rough coat should be remade. If the joints of cement are already
attacked, it is necessary to rejoint the stones or bricks and to replaster the unit. A defective condition
of some small boards, their replacement have to be carried out.


I.5. FIGHT AGAINST PREDATORS
Farmed fish have many enemies and compe-
Wild fish
titors, such as wild fish, frogs, insects and birds,
from which they should be protected (Figure 145
opposite). Protection is particularly important
while the fish are still very small. Pest control in
drained ponds, also called pond disinfection, has
several objectives, namely:
Ö To kill aquatic animal predators, such as car- Birds
Snails
nivorous fish, juvenile frogs and insects left in the
water puddles and in the mud, which would sur-
vive and feed on the young fish to be stocked; Froggs
Ö To eliminate all non-harvested fish, which
later would compete with your new stock for Snakes
space and food, especially if they reproduce wi- Crabs
thout control;
Turtles
Ö To destroy fish parasites and their interme-
diate hosts, such as snails, and thus help control Figure 145. Some predators of fish.
diseases.

Certain disinfection treatments have additional benefits such as improving water and bottom soil
quality or increasing the pond fertility.
Earthen fish ponds are most easily disinfected after their water has been drained as thoroughly
as possible, by gravity for drainable ponds.
By keeping the pond dry (preferably in warm, sunny weather). many undesirable will be elimina-
ted. The ultraviolet rays of the sun have a powerful sterilizing effect. Depending on air temperature, it
will be necessary keep the pond fully dry from 24 hours (at the minimum) to one month.
Some agricultural by-products can also be used to disinfect drained ponds cheaply whenever
they are locally available, for example rice bran (400 to 1000 kg/ha), crude sugar molasses (400 to
500 kg/ha) and tobacco dust or tobacco shavings (300 kg/ha). One will just spread the required
amount of by-product over the pond bottom. Then, one will flood with 5 to 10 cm of water for 10 to
15 days. It is best not to drain the pond but to fill it up, so as not to lose the fertilizing effect of the
organic disinfectant. Before applying tobacco dust or tobacco shavings, it is best to soak the sacks
in water overnight. This step will prevent the dust being blown away by wind during spreading on the
pond bottom. It is better to avoid the use of chemicals like lime.

I.6. SUMMARY

Ö Emphasis on:
Ö The daily visits for maintenance;
Ö The control of fish behavior and actions to be taken (ventilation, autopsy ...);
Ö The nutrition only if necessary;
Ö Maintenance of ponds with the cleaning and the fight against predators.

Once this work finished, it is enough to remake to run water in the pond and to fertilize it with
animal or vegetable compost, animal manure or vegetable matters like before. Once green water
become again, one can stocking again.


II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION
According to the quantity of harvested fish and their destination (sale or direct consumption), it
will be possible to store fish for a later consumption, or to market it, either alive, or fresh or preserved
or transformed.
If one wishes to keep alive fish, one will be able to put them either in small basins or fish ponds
builds with this use, or by using cages or grabbed (Chapter 09, paragraph III.3, p. 142). One will be able
to then take when it is wished fresh fish for consumption or the direct sales.
Local sale of fresh farmed table fish is the simplest and cheapest way of marketing. Usually
people prefer fresh to processed fish. But to ensure good quality and a good price, the fish should
be handled properly.
Before harvest, fish feeding have to be stop at least one day beforehand.
During harvest, the live fish will be handle carefully. If necessary transfer them quickly to a sto-
rage facility, for example, to remove any unwanted muddy flavour or to simplify or make more attrac-
tive selling arrangements.
After harvest: if muddy, the fish have to be rince well in clean water. It is best to kill the fish
quickly with minimum stress. As soon as a fish dies, it starts to decompose. This process is mainly
caused by the increased activity of bacteria, which rapidly multiply within the fish under favourable
conditions of food, temperature and humidity. Bacteria are especially numerous on the gills and in
the digestive tract of live fish. It is from there that decomposition will quickly spread to the whole
body as soon as a fish dies.
As soon as the fish are collected and killed, it is preferable to empty them and remove all the
internal organs and blood and/or to remove the gills (or to cut the head). It is necessary to preserve
the cleanliness of fish by washing them with clean water. One will avoid posing directly on the ground
and one will be able to protect them carefully, for example in cases or bags of plastic to protect them
from mud, dust, insects…
If one wants to sell it fresh, it should be sold as quickly as possible. Either one collects only the
quantity of fish which one thinks of being able to sell the same day, or one will keep them cool, in
the shade or covered with sheets of banana tree, of grass… The best is to obtain ice, but it is rarely
the case. On the other hand, one will never leave fish died in water because they will rotten quickly.
If one must transport them, the best is to avoid the hottest hours of the day and to travel early
the morning or even the night.
Although it is to better privilege the sale of fish fresh, in some cases, the treatment of fish may
be preferable. One will be able either to expose it to high temperature by cooking it, or to lower the
water content of fish by drying, salting or smoking (Figure 146, Figure 147 and Figure 148, p. 166).
9 Drying consists in removing the water from the surface and the flesh of prepared fish.
9 Salting consists to remove most of water present in the flesh of fish and to replace it by salt.
9 Smoking consists in removing most of the water contained in the flesh of fish by an expo-
sure to the smoke of wood.
When selecting a processing method, it is important to take into account the type of fish to be
preserved. Lean fish such as tilapias are much easier to process than oily/greasy fish such as catfish.
Large, deep-bodied fish are more difficult to process than small, slender fish.
There are several methods to dry or smoke fish, requiring investments and material more or
less important. We will not go here into the details. Various techniques can be found in the technical
handbooks of FAO.
As soon the process on fish is done, it will be important to store the dried or smoked fish pro-
perly:
Ö By keeping it cool and dry;
Ö By packing it tightly to protect it from air moisture (mould) and to delay the onset of rancidity of
fish fat;


Hanging from a line
hanging fish for between trees or poles
drying or smoking

Through the eyes

Hanging from a
rack of poles
Through the mouth of
throat

Hook in throat

Split open

Figure 146. Differents methods of natural drying of fish.
Hang fish vertically and spread damp cloth over
smoker during uses
Ö By protect it from
insect infestation, for
Smoke chamber example by placing it in
with the top
woven baskets lined with
covered with iron
rods or metal mesh plastic or strong paper;
if you use plastic bags,
Chamber 1
Firebox with a
keep them away from
perforated metal cover direct sunlight to avoid
moisture building up in-
Chamber 2 side.
Cut fire door (20 x It is important to
25 cm), but keep check regularly on the
the metal piece to quality of your stored fish
Firebox close box during and reprocess it as ne-
smoking cessary.

Figure 147. Example of smoking method of fish.
Barrel or box

Ö Take in mind that:
Ö To sell the fish, it must be prepared;
Ö The fish can be kept alive or
Layer fish with salt on top and Ö It can be smoked, salted or dried.
bottom and along sides

Figure 148. Example of salting system.


III. THE MANAGEMENT OF PONDS
Proper management consists of monitoring the fish ponds regularly, keeping good records and
planning ahead for the operation of the farm. On this basis, for example one can decide when to
fertilize your ponds.

III.1. FISH STOCKS AND USEFUL INDICES FOR MONITORING
It is important to monitor the fish stocks closely. For this it is necessary first to learn about the va-
rious indices or parameters which are commonly used to measure and compare the performances
of various stocks in fish farms such as their growth, production and survival.
The following terms are used to describe the size of a fish stock:
9 Initial fish stock which is the certain number and weight of fish stocked into the pond at the
beginning of the production cycle. Two parameters then are:
¾ Stocking rate which is the average number or weight of fish per unit area such as 2 fish/
m2, 2 kg fish/m2, or 200 kg/ha;
¾ Initial biomass which is the total weight of fish stocked into a specified pond such as
100 kg in Pond X.
9 Fish stock during production cycle which is the certain number and weight of fish present
in the pond. They are growing, although some of them may disappear, either escaping from the pond
or dying. An important parameter is then:
¾ Biomass present which is, on a certain day, the total weight of fish present in a pond.
9 Final fish stock which is the certain number or weight of fish at the end of the production
cycle, similarly:
¾ Final biomass which is the total weight of fish present at final harvest.
Concerning the changes in a fish stock at harvest or over a period of time:
Ö Output or crop weight is the total weight of fish harvested from the pond.
Ö Production is the increase in total weight that has taken place during a specified period. It is
the difference between the biomass at the end and the biomass at the beginning of the period. For
example, for a stocking of 55 kg, and a weight measured after 30 days of 75 kg, 75 - 55 = 20 kg.
Ö Yield is the production expressed per unit area. For example if 20 kg were produced in a 500 m2
pond, the yield during the period was 20 / 500 = 0.040 kg/m2 = 4 kg/100 m2 or 400 kg/ha.
Ö Production rate is the production expressed per unit of time (day, month, year, etc). For example,
if 20 kg were produced in 30 days, the daily production rate would be 20 / 30 = 0.66 kg/day.
Ö Equivalent production rate is the yield expressed per unit of time, usually per day or per year
= 365 days. It enables to compare productions obtained in various periods. For example 400 kg/ha
produced in 30 days are equivalent to (400 x 365) / 30 = 4 866.7 kg/ha/year. It may be also useful
to indicate the average daily production rate, which in this case is 4 866.7 / 365 = 13.3 kg/ha/day or
1.33 g/m2/day.
Ö Survival rate is the percentage of fish still present in the pond at the end of a period of time. It
should be as close as possible to 100 percent. For example, if there were 1200 fish at the beginning
of the period and 1 175 fish at the end, the survival rate during that period was
[(1 175 x 100) / 1200] = 97.9%; mortality rate was 100 - 97.9 = 2.1%.
A stock of fish is made of individuals. One can point out here the measurements taken on the
individuals for the follow-up of the pond (Chapter 09 paragraph V, p. 149).
Ö The average weight (g) obtained by dividing the biomass (g) by the total number of fish present.
Ö Average growth (g), i.e. increase in the average weight during one period of time given. It is
about the difference between the average weight at the beginning and the end of the period.
Ö Average growth rate, i.e. the growth (g) expressed per unit of time, generally a day. One speaks
then about daily growth rate, obtained by dividing the growth for one period given by the duration of
this period into days. It is calculated either for one period determined during the operating cycle, or
for the totality of this cycle.


Example: A pond (312 m²) have been stocking with 680 fish of an initial biomass of 5.6 kg. At the
end of the cycle of production (149 days), the harvest was of 43.8 kg for 450 fish. So:
Pond production = 43.8 - 5.6 = 38.2 kg
Yield = 38.2 / 312 = 12.24 kg/100 m2
Production rate = 38.2 / 149 = 0.26 kg/day
Equivalent production rate = (12.24 x 365) / 149 = 30 kg/100 m2/year
Survival rate = [(450 x 100) / 680] = 66%
Mortality rate = 100 – 66 = 34%
Initial average weight of the fish was of 5600 / 680 = 8.2 g,
and final average weight of 43800 / 450 = 97.3 g.
So, it is:
Average growth during the cycle of production = 97.3 – 8.2 = 89.1 g
Daily groqth rate = 89.1 / 149 = 0.6 g/day.

III.2. THE ExPECTED YIELDS
Yields depend on the species used. However, one can give an estimate of the expected weight
per pond, depending on the species.
Let us consider a pond of 400 m2 containing Nile tilapia (polyculture with the African catfish
Clarias gariepinus), of weight to loading ranging between 5 and 10 g for the two species. At the end
of 7 months of extensive farming (fish given up with themselves, without any contribution), one can
expect a production of approximately 30 kg (either in the 750 kg/ha/an). For the same duration in a
little less extensive (more or less fertilized pond), the annual production will vary from 50 to 100 kg,
that is to say the equivalent from 1.2 to 2.5 tonnes/ha/an. That will go up to 10 tonnes/ha/an in far-
ming with a predator, that is to say 150 kg per pond of 400 m2 over 6 months.
In polyculture which associates Heterotis niloticus and Heterobranchus isopterus, the juveniles
of H. isopterus are introduced with the maximum density of 20 individuals per are into the ponds of
production of tilapia. These systems produce yields of about 4 to 15 t/ha/an, according to the level
of fertilizer contribution.
One can thus obtain 150 kg of fish for a pond of 100 m2 per year, i.e. approximately 12 kg per
month for 100 m2 of pond. For a small pond of 200 m2, which is the minimum, one will be able to thus
have approximately 24 kg per month of fish, that is to say 0.8 kg per day.

III.3. THE MANAGEMENT OF HARVESTS
The management of harvests will depend on the mode of approach. But in most cases, the vil-
lagers will have by themselves to regulate this aspect. This management will depend on the quantity
of ponds, but it seems adequate to have at least 3 ponds to ensure a quasi monthly harvest with fish
of consumable size.
If one puts fry in different ponds at different times of the year, one will be able to harvest them
at different periods also and, thus, a quantity not too important of fish at the same time. One will be
able to fish all the year.
If there are 4 ponds and a good supply of fingerlings, it can be stocked in each pond at different
month of the year and harvest the pond every 3 to 6 months later according to the size at which
fish seem consumables (Table XXXVI, p. 169). Indeed, depending on location, fish of 60 to 80 g will be
consumed and a tilapia can reach this size in 3 months. The duration and the time of growth will also
depend on the follow-up of growth.
By estimating 4 ponds of 400 m2, which can produce up to 50 kg per month by pond, one will be
able to produce up to 500 kg per year. In a country where the fish is sold to 5 US$/kg, that will make


Table XXXVI. Examples of management for 4 ponds.
Harvest after 3 months (on left); After 4 months (on right). The color are related to the diffe-
rent steps described in the general frework of setting the ponds.

1st exemple 2nd exemple
Month Pond 1 Pond 2 Pond 3 Pond 4 Harvest Pond 1 Pond 2 Pond 3 Pond 4 Harvest

1

2

3
1
4
2 1
5
3 2
1st year

6
4 3
7
5 4
8
6
5
9
7
6
10
8
7
11
9
8
12
10
13
11 9
14
12 10
15
13 11
16
14 12
17
15
13
2nd year

18
16
14
19
17
15
20
18
16
21
19
22
20 17
23
21 18
24
22 19
Stocking fish Growing Drain and harvest
Maintenance of ponds Pond not in use


it possible to obtain for the groups the equivalent of 2500 US$ per year, that is to say approximately
200 US$ per month.
The distribution of harvests between the beneficiaries will be based according to the type of
associations and grouping which was adopted. This can vary according to the countries, the ethnic
groups and social structures present in the places where the various projects will be implemented.

III.4. SEVERAL KINDS OF PRODUCTION COSTS
An owner of pond must first of all pay the fixed factors of production (capital equipment at
lifespan higher than a cycle of production (ground, water, ponds, nets…)) and variables (articles of
operation (consumable, labor)). Any expenditure devoted to the exploitation of the fish farm belongs
to the costs of this type, and is generally called costs of exploitation. They are thus described as:
9 The fixed operating costs remain the same whatever the amount of fish produced in a
given farm. They are related to the fixed factors of production. The most important of these are the
depreciation and interest costs associated with the investment and the costs of annual water rights,
lease on land, licences and other fixed payments such as interest on loans.
9 The variable operating costs or running costs are those costs that are directly related to
the production of the farm.
A part from the fixed cost of pond construction (often built through the farmer’s own labour),
costs are very low and almost negligible for subsistence farmers. However, it is important to identify
the costs as realistically as possible, to avoid wasting time, money or other resources on inefficient
or unprofitable operations.
As time goes on, long-lasting factors of production such as ponds, buildings, equipment and
vehicles wear out.
In the short term, they are kept in serviceable condition through maintenance, including the pur-
chase of materials and spares, and labour required for repairs.
Table XXXVII. Useful life of fish farm structures After a certain number of years
and equipment (in years, assuming correct utilization). they have to be replaced or re-
novated. This period is called the
Structure / equipement Years useful life. Useful life varies, as
Pond, earthen 30 shown in Table XXXVII (opposite).
Some factors such as buildings
Channels, earthen 20
and ponds have a very long use-
Hard wood, treated 10 ful life, while other factors such as
Masonry 20 wheelbarrows or nets may wear
Pond structures Concrete 20 out within only a few years.
PVC pipes 10 III.5. RECORD KEEPING AND
Reinforced, concrete pipes 20
ACCOUNTING
Wood / thatch roof 4
Fish farmers need only keep
Buildings Sundried clay bricks 6
simple records, which should
Fired bricks or concrete blocks 20 enable them to know, month by
Boat wooden 8 month:
Fence, wire / treated wooden posts 10
9 The total amount of money
spent on fish farming and per each
Fishing net 5 pond;
Hapas 2 9 The total number (and
Cast nets, dip nets 2 weight) of fish stocking initially;
9 The total number (and
Wheelbarrow 3
weight) of fish harvested;
Workshop tools (saw, hammer…) 5 9 Number of fish given either
Pick, shovel, axe 2 to family for consumption or in ex-
Buckets, barrel 1
change of casual labour;


9 The total number (and weight) of dead fish;
9 The total number (and if possible weight) of any fish sold for cash (cash income) and/or
bartered for other commodities (equivalent value as income).
At the end of the year, the above records will provide information on:
Ö The total value of the fish given away;
Ö The total value of all fish harvested;
Ö The amount gained (net profit) or lost (net loss) through fish farming.
A simple form can be used day by day to record for one month all activities around the fish farm,
every amount of money spent and all the details of fish production (Appendix 01, p. 189). This is called
the daily record form. You may prepare a form similar to the example below in a small school copy-
book, using two facing pages per form.
Any activity, such as work done on the fish farm and items of equipment purchased for it, should
be immediately noted down together with such relevant data as money spent, number of fish har-
vested, and number of fish given or sold. It is important to note these details as soon as they are
available. At the end of the month, one will just have to sum the different columns to get the monthly
totals.
In the same way, one will be able with the end of the year, by making the total of the months, to
make an annual statement of account.

III.6.THE FORMATION
In order to promote and to ensure the continuity of the project correctly, trainings are necessary
for the beneficiaries and future operators of the ponds. The topics approached will be:
Ö Importance of fish in the food
The animal proteins are essential for a good growth of the children as well as the health of the
parents.
Ö Importance of the rivers: water and health
Water is one of the major fields for the development of the human diseases. Several parasites
and diseases pass through the water and the lack of hygiene: malaria, cholera, schistosomiasis, to
name just a few of them. We will return in the next chapter on health and the ponds. One will not
detail here these two topics which are well developed in several books.
Ö How to build the ponds
One will be able to take the various stages listed in this handbook.

IV. PONDS AND HEALTH
Water being the field in which several parasites and vectors of serious diseases pass through or
come from. The ponds being water points, it is appropriate to take care of certain rules to limit the
problems of disease and health.
A mosquito species and several species of freshwater molluscs transmit diseases can be fatal.
It is malaria (mosquito) and schistosomiasis (snail). If plants or grasses are too dense on the edges
of ponds or in them and in the enclosure, snails and mosquitoes can live and proliferate very easily.
Thereforeit will be necessary to periodically remove plants that are there and mow the dikes. Herbs
edges should not hang in the water so that fish can effectively eliminate insects or others animals
(Figure 149 and Figure 151, p. 172).
It is strongly advised not to use the ponds or enclosures as toilets (Figure 150, p. 172). It is to better
use a latrine if it is present or to build one to at least 10 m of any edge of the ponds or enclosure and
source of water supply. If one is taken of a pressing need during work close to the ponds or the en-
closures, of the river which feeds them, of the supply channel or the inlet, a distance of at least 10 m
is the minimum to satisfy this need. In the same way, it will be necessary to avoid making its needs
on a heap for compost or in the vicinity. A pond is not either a place with a water for domestic use,
like drink or washing. It is necessary to transmit to the people having access to the infrastructures
these minimal rules of hygiene.


Figure 149. Mosquito and snail. Figure 151. Cleaning of the dikes.

m yes
10

m
10

no yes

no

no

10 m
no

yes
Figure 150. Several human behavior to avoid nearby the ponds.


General summary
All the steps to achieve the production of fish for subsistence is shown in the diagram
next page.

The fishfarming system choose is this of production, semi-intensive, of self-consump-
tion to artisanal, using polyculture rather than monoculture that request external food
input and a more important follow-up if one want an interesting production.

The evaluation of the ecosystem in all its components, human beings included, is of
a major importance in order to see which are the actions to propose to ensure a better
“wellbeing”, mainly of food safety but also of health and water and sanitation. Preferably,
two specialists will be necessary with priority for the biological aspects.
The whole of collected information will allow:
Ö To know the statement of the zone where the intervention must take place;
Ö To know the available resources usable and their current use;
Ö To know the communities and social structures.

The goal being to have the elements to propose a solution allowing a good appropria-
tion of the project by the populations, if the various components make it possible to affirm
that fishfarming is a solution for the zone considered.

The source of fish to be used and the drainage basin where the action is underta-
ken are of highest importance, this, because of the risks incurred by the introduction of
fish and the national and international legislative aspects concerning the biodiversity It is
not either because a species was already introduced into the zone of intervention, that it
should necessarily be used.

The choice of the village must take into account:
Ö Vulnerability of the population;
Ö Logistics;
Ö Water resources;
Ö Motivation of the villagers.


0
Assessment
3 months
3 months
Selection

Ponds
Laying out plan
Purchases of the
equipment


Time



Purchases of
fishing nets
or hapas


Fish farming
juvenils of tilapia Resumption of a cycle

« Green water » Maintenance and
ponds
water of predators
Follow-up
of the fishes
Duration: predators
4 to 12 months

of fishes
fishes and harvest
Maintenance and
Duration: draining


The site selection is the most important step for a fish pond. It have to take into ac-
count:
Ö The water: quantity and quality;
Ö The soil: impermeable;
Ö The topography: Weak slope and zone of emergence of sources.

The choice will go to diversion ponds supplied with water by gravity. rectangular, ar-
ranged en parallel, of a size of 100 to 400 m2.

Emphasis on:
Ö The cleaning of the site that must be done well;
Ö The picketing which must be precise for the slopes;
Ö The control and management of the water by channels;
Ö The importance of dykes, their strength and their size and although compacted;
Ö The choice of a monk for draining ponds;
Ö The total isolation of the ponds from the outside for better control;
Ö The soil conservation upstream.

Ö For the fertilisation, the preparation of aerobic and anaerobic compost is important.
Ö The expectation of a « green water » indicate that the pond is ready for ensemense-
ment.

After fertilization, the steps are:
Ö The collect of specimens in the wild or by production of fingerlings of tilapia;
Ö The stocking of ponds with tilapia;
Ö The growth monitoring;
Ö The collect of predators in the wild;
Ö The stocking with predators;
Ö The monitoring and partial harvest of fish;
Ö Then, after several weeks, the draining and the complete harvest of fish.


African freshwater fish species are numerous and many may be used in fishfarming.
The choice of the species will be done regarding the geographic location of the ponds
(ichthyoregions). However, in case of subsistence, one will choose:
Ö A tilapia for the main production. Strong fish, highly plastic and adaptable to environ-
mental conditions with elaborated parental care, which are opportunistic about feeding,
with:
Ö A piscivorous species which will be the predator for the reproduction control of tilapia;
Ö One will also used other species in the pond as omnivorous and/or herbivorous spe-
cies.
For the predator, the proportion must be approximately 13 % of the weight of put ti-
lapia. Globally, ten fish of approximately 7/8 cm for a hundred tilapia having reached 6/7
cm are enough. The stocking of predators will be done approximately one month after
stocking the pond in tilapia.
The density of tilapia have to be of 0.5 ind/m2

One of the main principles will be to use only non-destructive gear for the local wildlife.
Care should be taken to respect the laws relating to fishing. Where appropriate, per-
mits have to be requested from the local authorities.

Emphasis on:
Ö Fishing methods and precautions to keep fish in good condition and avoid problems
and local legislation;
Ö The biology of the species and they provide for good production, breeding, feeding,
behavior, both for good growth and in the choice of density;
Ö The transport of fish and to provide care in order to avoid a loss of fish which may be
the complete number of fish.

To insure a good production, emphasis on:
Ö The daily visits for maintenance;
Ö The following of the fish;
Ö The control of fish behavior and actions to be taken (ventilation, autopsy…);
Ö The complementary nutrition only if necessary;
Ö Maintenance of ponds with the cleaning and the fight against predators.

Ö The fish can be kept alive.
Ö To sell the fish, it must be prepared. If it is not sell fresh, it can be smoked, salted or
dried.

We thus have a master plan of a system allowing to produce consumabl) fishes in the
shortest possible time and at a lower cost to compensate a lack of animal proteins.


References
Quoted here are only a few references. This list is not, of course, exhausitive. The reader may
also find on the website of the FAO (www.fao.org) various documents relating to fisheries and aqua-
culture.

Arrignon J., 1993. Aménagement piscicole des eaux douces, 4ème édition. Technique & documen-
tation - Lavoisier - Paris. 631 p.

Bard J., de Kimpe P., Lemasson J. & Lessent P., 1974. Manuel de pisciculture tropicale, CTFT, PARIS.

Billard R. (ed), 1980. La pisciculture en étang, Paris, France : INRA, 434 p.

Coche A.G. & Van der Wal H., 1983. Méthode simple pour l’aquaculture Pisciculture continentale :
l’EAU. FAO collection formation, 1 volumes 112 p.

Délincé G., 1992. The ecology of the fish pond ecosystem with special reference to Africa. Kluwer
Academic (Publ.), Dordrecht, Netherlands : 230 p.

Egna H.S. & Boyd C.E., 1997. Dynamics of pond aquaculture, Boca Raton, USA : CRC Press, 437 p.

FAO, 1997. Review of the state of world aquaculture. FAO Fisheries Circular. N°886, Rev. 1. Rome,
Italy. FAO Inland water resources and aquaculture service, Fishery Resources Division.

FAO, 2000. Simple methods for aquaculture. FAO Training Series.

FAO, 2006. Aquaculture production 1986-1992. FAO/FIDI/C815 (Rev. 6), 216 p.

FAO, 2007. Situation mondiale des pêches et de l’aquaculture. (SOFIA).

Froese, R. and D. Pauly. (Eds). 2008. FishBase. World Wide Web electronic publication.
www.fishbase.org, version (06/2008)

Jauncey K. & Ross B., 1982. A guide to tilapia feeds and feeding. Institute of Aquaculture, University
of Stirling, Scotland, 111 p.

Lazard J., 1990. L’élevage du tilapia en Afrique. Données techniques sur sa pisciculture en étang. p.
5-22. In : Méthodes artisanales d’aquaculture du tilapia en Afrique, CTFT-CIRAD, 82 p.

Lazard J. & Legendre M., 1994. La pisciculture africaine : enjeux et problèmes de recherche. Cahiers
Agricultures, 3 : 83-92.

Lazard J., Morissens P. & Parrel P., 1990. La pisciculture artisanale du tilapia en Afrique : analyse
de différents systèmes d’élevage et de leur niveau de développement. p. 67-82. In : Méthodes
artisanales d’aquaculture du tilapia en Afrique, CTFT-CIRAD, 82 p.

Lazard J., Morissens P., Parrel P., Aglinglo C., Ali I. & Roche P., 1990. Méthodes artisanales d’aqua-
culture du tilapia en Afrique, Nogent sur Marne, France : CTFT-CIRAD, 82 p.


Legendre M. & Jalabert B., 1988. Physiologie de la reproduction. In : C. Lévêque, M.N. Bruton & G.W.
Ssentongo (eds). Biologie et écologie des poissons africains d’eau douce. ORSTOM, Travaux et
Documents, 216 : 153-187.

Oswald M., 1996. Les aménagements piscicoles du Centre-Ouest de la Côte d’Ivoire. p 383-400 In
LavigneDelville P. et Boucher L., 1996. Les bas-fonds en Afrique Tropicale Humide, GRET-CTA
Coop. Française. 413 p.

Oswald M., Glasser F. & Sanchez F., 1997. Reconsidering rural fishfarming development in Africa. p
499-511 vol II In Tilapia Aquaculture, Proceedings from the Fourth International Symposium on
Tilapia in Aquaculture Orlando (Floride- USA, ed Fitzsimmons K. Nraes, New York, USA.

Otémé J. Z., Hem S. & Legendre M., 1996. Nouvelles espèces de poissons chats pour le développe-
ment de la pisciculture africaine. In : M. Legendre & J. P. Proteau (eds). The biology and culture
of catfishes. Aquat. Living Resour., 9, Hors série, 207-217.

Paugy P. & Lévêque D., 2006. Les poissons des eaux continentales africaines. Diversité, écologie,
utilisation par l’homme. 2nd édition. IRD. 521 p.

Pouomogne V., 1998. Pisciculture en milieu tropical africain : comment produire du poisson à coût
modéré (des exemples du Cameroun). Presse universitaire d’Afrique, Yaoundé . 235 p.

Pullin R.S.V. & Lowe-McConnell R. H., 1982. The Biology and Culture of tilapia. Proceedings of the
International Conference Held 2-5 September 1980 at the Study and Conference Center of the
Rockefeller Foundation, Bellagio, Italy, Sponsored by the International Center for Living Aquatic
Resources Management, Manila .

Pullin R.S.V., Lazard J., Legendre M., Amonkothias J.B. & Pauly D., 1996. Le troisième symposium
international sur le tilapia en aquaculture, Manila, Philippines : ICLARM/CIRAD-EMVT/ORSTOM/
CRO. Proceedings of the international symposium on tilapia in aquaculture, 630 pp.

Sclumberger O., 1997. Mémento de pisciculture d’étangs. 3ème édition, CEMAGREF, France, 238 p.

Wilson R. P. & Moreau Y., 1996. Nutrien requirements of catfishes (Siluroidei). In : M. Legendre & J. P.
Proteau (eds). The biology and culture of catfishes. Aquat. Living Resour., 9, Hors série, 103-111.

Wolfarth G. W. & Hulata G. I., 1981. Applied genetics of tilapias. ICLARM Studies and Reviews, 6,
26 p.

Useful web sites:

www.fao.org

www.fishbase.org

www.ird.fr/poissons-afrique/faunafri/


Glossary
A B
Abiotic: Physical factor that influences the de- Bacteria: Very small unicellular organism
velopment and / or survival of an organism. growing in colonies often large and unable
Abundance: Quantitative parameter used to to produce components of carbon through
describe a population. The enumeration of photosynthesis; mainly responsible of rot-
a plant or animal population, is generally ting vegetable matter and dead animals.
impossible, hence the use of indicators. Benchmark: see Point, reference
By extension, abundance means a num- Benthos: Groups of vegetable and animals or-
ber of individuals reported to a unit of time ganisms in or on the surface layer of the
or area, within a given population, recruit- bottom of a pond. Associated term: ben-
ment, stock, reported to a unit of time or thic. Opposite: pelagos.
area.
Bicarbonates: Acid salts of carbonic acid (see
Amino acid: Class of organic components carbonate) solution in water, they contain
containing carbon, hydrogen and oxygen, the ion HCO3 as calcium bicarbonate
associated in large numbers, they are pro- Ca(HCO3)2 for example.
teins, some of them play an essential role in
fish production. Bioaccumulation: Catch of substances - e.g.
heavy metals or chlorinated hydrocarbons
Aerobic: Condition or process in which ga- - resulting in high concentrations of these
seous oxygen is present or necessary. substances in aquatic organisms.
Aerobic organisms obtain their energy for
growth of aerobic respiration. Biocenose: Group plants and animal forming
a natural community, which is determined
Anaerobic: Sayd for conditions or processes by the environment or the local ecosystem.
where gas oxygen is not present or are not
necessary. Biodiversity: Variation among living organisms
from all sources including, inter alia, terres-
Anoxic: Characterized by the absence of oxy- trial, marine and other aquatic ecosystems
gen. In a anoxic environment, the mainte- and the ecological complexes of which
nance of aerobic respiration is impossible, they are part: this includes diversity within
consequently, the life is limited to the pre- species, between species and ecosystem.
sence of organizations whose metabolism
is ensured by other mechanisms (fermen- Bioethics: Part of morality concerning research
tation, anaerobic breathing like the sulfato- on life and its uses.
reduction, bacterial photosynthesis…). Biomass: (a) Total live weight of a group (or
Aquaculture: Commonly termed ‘fish farming’ stock) of living organisms (e.g. fish, plan-
but broadly the commercial growing of kton) or of a definite part of this group
marine or freshwater animals and plants in (e.g. breeders) present in a water surface,
water. The farming of aquatic organisms, at a given time. [Syn.: stock present].
including fish, mollusks and aquatic plants, (b) Quantitative estimate of the mass of the
i.e., some form of intervention in the rearing organisms constituting whole or part of a
process, such as stocking, feeding, pro- population, or another unit given, or contai-
tection from predators, fertilizing of water, ned in a surface given for a given period.
etc. Farming implies individual or corporate Expressed in terms of volume, mass (live
ownership of the farmed organisms. weight, dead weight, dry weight or ashes-
off weight), or of energy (joules, calories).
Aufwuchs: German term indicating the layer of [Syn.: charge].
algae adhering on rocks.


Biotic: In relation to the life and the living matter. sents the course of a level line such as it
Biotope: Zone or habitat of a particular type, exists on the ground.
defined by the organisms (plants, animals, Cyst: (a) Phase of very resistant, not-mobile,
micro-organisms) which live typically there, deshydrated, inactive for free or parasitic
e.g meadow, wood, etc; or, with more small organisms, in response to unfavourable en-
scales, a microhabitat. vironmental conditions. (b) Not-alive mem-
Breeders or brood fish: Adult animal being brane surrounding a cell or a group of cells.
used to ensure the reproduction.
D
Broodstock: (Stock of) Stock of fish intended
for the reproduction, preferably being the Demersal: Animal living near the bottom but not
subject of a special management in distinct permanently.
ponds. Dimension or elevation: Vertical or height dis-
C tance above a “horizontal” plane of given
reference; See Elevation/level and Level/
Calcium carbonate limestone or Limestone: Reference plan.
Natural rock made up mainly of carbonate Digestibility: Relative speed and degree to
calcium CaCO3. which a food is digested and absorbed.
Carbohydrate: Composed organic constituted
of carbon, hydrogen and oxygen, such as E
sugars, starch and the cellulose; The energy
Ecology: Connect sciences concerned with the
food generally least expensive, in particular
relations existing between organisms and
for omnivorous and herbivorous fish.
their environment.
Carbonate: Carbon salt of dioxide, a compound
Ecosystem: Set (or system) with natural struc-
formed of carbonic gas (CO2) in contact
tures and distincts relations which link biotic
with water; for example calcium carbonate,
communities (of plants and animals) to one
CaCO3 .
another and to their abiotic environment.
Cellulose: Organic component which consti- The study of an ecosystem provides the
tutes the essential part of the solid structure methodological basis for a synthesis of the
of the plants; it is also present in the animal complex relationships between organisms
body. and their environment.
Charge: Level at which the water is kept or may Elevation or level: General terms indicating the
be high, allowing for example to flow to vertical distance or height above a reference
lower levels or browse pipes. plan, such as the mean level of the seas (see
Colloid: Particle of very small dimension (from altitude) or an arbitrarily selected horizontal
0.5 to 1 micron), either mineral (for example plan (see dimension); calculated according
colloidal clay), or organics (for example hu- to topographic data.
mus). Embankment: (a) Zone of which it is necessary
Conductivity: Measuring the concentration of to raise the level of the ground to a necessa-
ions or salts in water in direct relation to the ry height while bringing ground. (b) Ground
facility with which it conducts electricity. itself thus brought back.
Generally water with high conductivity has a Endemic: Specific or indigenous in an area.
good buffering capacity. It varies with tem- Qualify disease-causing agents and di-
perature and is expressed in Siemens (S) seases which, at all times, are present or
per meter at 25°C. generally prévalents in a population or a
Conflict of use: Emerging conflict between dif- geographical area.
ferent users of the same environment which Energy: In aquaculture: Usually relate to the
may have the same interests or competitors. food needs for the aquatic organisms, ex-
Contour line: (a) Imaginary line connecting all pressed by a quantity of joules/calories per
the points of the identical level of altitude. day necessary to ensure the essential pro-
(b) Line which joint all the of the same points cesses of life, i.e. the growth and the repro-
dimensions on a plan or a chart; it repre- duction.


Equidistance of the level lines: Difference in nity, through which energy is transferred by
rise between two close level lines. food way. Energy enters the food chain by
Ethology: Animal behavior science. the fixation by the primary producers (green
plants for the major part). It passes then to
Eutrophic: Rich in nutrients, phosynthetic pro- the herbivores (primary consumers) then
ductive and often deficient in oxygen under to the carnivores (secondaries and tertiary
warm weather. consumers). The nutritive elements are then
Eutrophication: The enrichment of a water recycled towards the primary production by
body in nutritive elements, in a natural or the detritivores.
artificial way, characterized by wide plank- Fry: A young fish at the post-larval stage. May
tonique blooms and a subsequent reduction include all fish stages from hatching to fin-
in the dissolved oxygen content. gerling. An advanced fry is any young fish
Extrusion: Process of transformation of food from the start of exogenous feeding after
material is subjected for a very short time the yolk is absorbed while a sac fry is from
(20 to 60 s) at high temperatures (100 to hatching to yolk sac absorption.
200°C) at high pressures (50 to 150 bars),
and a very intense shear . G
F Gauge: Model of wood being used to give the
wanted form, for example with a channel or
Fatty-acid: Formed lipid of a more or less long a dike.
hydrocarbon chain comprising a carboxyl Gamete: Reproductive cell of a male or female
group (-COOH) at an end and a methyl living organism.
group (-CH3) at the other end.
Gene: ÉlémentBasic element of the genetic in-
Fecundity: In general, potential reproductive heritance contained in the chromosomes.
capacity of an organism or population, ex-
pressed by the number of eggs (or offspring) Genetics: Science for the purpose of studying
produced during each reproductive cycle. issues concerning the transmission of traits
from parents to offspring in living beings.
Relative fecundity: Number of eggs per
unit fresh weight. Genotype: Genetic structure of an organism at
the locus or loci controlling a given pheno-
Absolute fecundity: Total number of eggs type. An organism is homozygote or hetero-
in a female. zygote at each of the loci.
Feedingstuff, supplementary: Food distribu- Gonado-somatic ratio: Ratio of the weight of
ted in addition to food presents naturally. the gonades to the total live weight (or of
Feedingstuff, composed: Food with several the total live weight to the weight of the go-
ingredients of vegetable or animal origin nades), usually expressed like a percentage.
in their natural, fresh or preserved state,
or of derivative products of their industrial H
transformation, or of organic or inorganic
substances, containing or not additives, Halieutic: Science of the exploitation of the
intended for an oral food in the shape of a aquatic alive resources.
complete feedingstuff. Herbivore: Animal which feed mainly on plants.
Fermentation: The anaerobic degradation of or- Hormone: Chemical substance produced in
ganic substances under enzymatic control. part of an organism and generally conveyed
Fingerling: Term without rigorous definition; by blood in another part of this organism,
says for young fish starting from advanced where it has a specific effect.
fry until the one year age starting from the Humus: Decomposed organic matter present in
hatching (independently of the size). [Syn.: organic manures, composts or grounds, in
juvenile]. which the majority of the nutritive elements
Food chain: Simplistic concept referring to the are available for fertilization.
sequential series of organisms, pertaining Hybridization: Fecundation of a female of a
to successive trophic levels of a commu- species by the male of a different species.


Hydraulics: Relating to water, the action or the components (fats and similar substances)
energy utilization related to its movements. largely present in the living organisms; the
lipids have two principal functions: energy
I source and source of certain food compo-
nents (fatty-acids) essential to the growth
Ichtyology: The study of fish.
and survival.
Ichtyophagous: Animal feeding mainly on fish.
[Syn.: piscivorous]. M
Indigenous: Native of a country or a place. Macrophagous: Living organism which feeds
[Syn.: native]. on preys having a size larger than that of its
Irrigation sluice: Work derivation placed on a mouth. Opposite: microphagous.
feeder canal to divert its flow into two (type Macrophyte: Relatively large vascular plant
in T) or in three (type in X) parts, or to in- by comparison with the microscopic phy-
crease the water level in a section of the toplankton and the filamentous algae. The
channel, or to control the water supply with basic structure of a aquatic macrophyte is
height of the water supply of a pond. visible with the eye.
J Maturation: Process of evolution of the go-
nades towards maturity.
Juvenile: Stage of the young organism before
Metamorphosis: All changes characterizing
the adult state. [Syn.: fingerling].
the passage of the larval state in a juve-
K nile or adult state for some animals. These
changes concern at the same time the form
and physiology and is often accompanied
L by a change of the type of habitat.
Larva, larvae: Specific stage to various ani- Mesocosme: Ecosystem isolated in a more or
mals, which is between the time of hatching less large enclosure from a volume from wa-
and the passage at the juvenile/adult form ter from one to 10 000 m3. Mainly used for
by metamorphosis. the production of alive preys in earthenware
Level: see Elevation. jars, basins, pockets plastic, ponds and en-
closure.
Level or reference plan: Level or plan used on
several occasions during a particular topo- Metabolism: Physical and chemical processes
graphical survey and by report to which the by which the food is transformed into com-
raised lines or points are defined. plex matter, the complex substances are
decomposed into simple substances and
Levelling: Operation consisting in measuring energy which is available for the organism.
differences in level in various points in the
ground with topographical survey. Milt: Mass genital products. Said also for the
sperm of fish.
Life cycle: The sequence of the stages of the
development of an individual, since the Monoculture: Farming or culture of only one
stage egg until death. species of organisms at the same time.

Line of saturation: Upper limit of the wetland in Mulch: Made non-dense cover organic residues
an earthen dike partially submerged. (for example cut grass, straw, sheets) which
one spreads on the surface of the ground,
Line of sight: Imaginary line from the eye of the mainly to preserve moisture and to prevent
observer and directed towards a fixed point, bad grasses from pushing.
it is always a straight line, also called «line
of sight.» Mulching: Placement of a layer of vegetable
matter, in order to protect young plantations
Limnology: The study of the lakes, ponds and (see Mulch).
other plans of stagnant fresh water and their
biotic associations. N
Lipid: One of the main categories of organic
Nekton: Animal whose swim actively in a pond;


Capable of a constant and directed mobility, Nutrition: All processes by which an animal
such as for example the insects and fish. (or a plant) absorbs and uses the nutritive
Niche: Ecological role of a species in a com- food or elements; The act or the process by
munity; conceptualized as the multidimen- which the organism is feed.
sional space whose coordinates are the va-
rious parameters representing the condition O
of existence of the species and to which this Oligotrophic: Qualify an environment where the
one is limited by the presence of competi- concentration in nutritive elements (= nu-
tors species. Used sometimes improperly trients) is low.
like the equivalent of microhabitat, referring
Omnivore: Animal which feed at the same time
to the physical space occupied by a spe-
on vegetable and animal matters.
cies.
Ontogeny: The early life history of an organism,
Food niche: Role of a fish in a system of
i.e., the subsequent stages it passes from
farming with regard to the consumption of
the zygote to the mature adult. Associated
food.
term: ontogenetic.
Ecological niche: Concept of the space
Oxidation: Chemical reaction by which, for
occupied by a species which includes not
example, there is an oxygen contribution.
only physical space but also the functional
part played by the species. A given spe-
cies can occupy various niches at different
P
stages of its development. Parthenogenesis: Reproduction from a female
Nitrate: Final product of the aerobic stabiliza- gamete, without fertilization by a male ga-
tion of organic nitrogen; Its presence in wa- mete (e.g. at the rotifers).
ter is indicative of an organic enrichment of Pelagos: It is the whole of the aquatic orga-
agricultural or industrial origin. Often used nisms which occupy a “water column”. It
as manure in culture of pond. thus includes the nekton and the plankton.
Nitrite: First stage in the oxidation of the am- Associated term: pelagic. Opposite: ben-
monium excreted by the aquatic organisms thos.
as final product of metabolic degradation. Perennial: It is said terrestrial vegetation which
The nitrite inhibits the fixing of oxygen by growths and survives more than one year
hemoglobin and becomes thus toxic for and which has usually leaves all the year.
fish. The shellfish are less affected because
Periphyton: Associated Microalgues and mi-
haemocyanin only is partially inhibited. For
cro-organisms living attached to any immer-
a given concentration, the nitrite is however
sed surface.
more toxic in freshwater than in marine or
brackish water. pH: Coefficient used to characterize the acti-
vity of the hydrogen ions in a solution or a
Nitrogenize: Gas element, without odor which
soil. The pH of pure water is equal to 7 and
constitutes 78% of the terrestrial atmos-
characterizes a neutral solution. A solution
phere; Present in all living tissue. In gas
having a pH lower than 7 is known as acid,
form, it is almost inert.
while a solution with pH higher than 7 is
Nitrogen, ammoniacal: Special term referring known as alkaline.
to the total weight of nitrogen in ionized
Phenotype: Physical or external appearance
form NH4+.
of an organism in contrast with its genetic
Nursery: Protected place for the rearing of constitution. Characters of an individual
young after metamorphosis in the hatchery which can be measured and observed.
and conducted before passage from the ex-
Photoperiod: Period lit, naturally or artificially,
ternal environment.
and considered from the point of view of the
Nycthemeral: Succession of the day and the biological phenomena associated with the
night of 24 hours which rhythm periodic va- light.
riation of the physiology of the plants and
the animals.


Photosynthesis: (a) Process by which the green of speed appearing when water moves
plants containing chlorophyl transform solar through a pipe or any other hydraulic work.
energy into chemical energy, by producing Probiotic: All the bacteria, yeasts or algae
organic matters starting from minerals. (b) added to some food products and which
Mainly production of composed of carbon help with the digestion of fibers, stimulate
starting from carbonic gas CO2 and water, the immune system and prevent or treat
with oxygen release. gastro-enteritis.
Phylogeny: Characterize the evolutionary his- Protein: Composed organic whose molecule is
tory of the groups of living organisms, in of important size and of which the structure
opposition to ontogeny which characterizes complex, made by one or more chains of
the history of the development of the indivi- amino-acids; essential to the organism and
dual. Associated term: phylogenetic. the functioning of all the living organisms;
Phytobenthos: Benthic flora. The food proteins are essential for all the
Phytoplankton: Unicellular algae living in sus- animals, playing a part of reconstituting tis-
pension in the water mass. Vegetable com- sue or energy source.
ponent of the plankton. Protozoa: Very small unicellular animal orga-
Piscivorous: Animal feeding mainly on fish. nisms, living sometimes in colonies.
[Syn.: ichthyophagous].
Q
Plan: Imaginary plane surface; any straight line
connecting two unspecified points of a plan
is located entirely in this plan. R
Plankton: All organisms of very small size, ei- Raceway: Basin with the shape of circuit used
ther plants (phytoplankton), or animals (zoo- for the farming in eclosery.
plankton), which live in suspension in water. Ration: Total quantity of food provided to an
Planktivorous: Animal feeding on phyto- and/or animal during one 24 hours period.
of zooplankton. Recruitment: Process of integration of one new
Plasticity: (a) Capacity which has a soil to be- generation to the global population. By ex-
come deformed without breaking and to tension, the new class of juveniles itself.
remain deformed even when the deforming Repopulation: Action to released in large num-
force does not act any more. (b) Ability of ber in the natural environment of the orga-
a trait in an organism to adapt to a given nisms produced in eclosery, with an aim of
environment. reconstitution of impoverished stocks.
Point, lost: Temporary topographic point of Resilience: Refer to the aptitude of an ecologi-
reference which one carries out the survey cal system or a system of subsistence to be
between two definite points; It is not used restored after tensions and shocks.
any more when the statements necessary
Respiration: Process by which a living orga-
were made.
nism, plants or animal, combines oxygen
Point, reference: Point usually fixes identified and organic matter, releasing from energy,
on the ground by a reference mark placed at carbonic gas (CO2) and other products.
the end of a line of sight. (see Benchmark). [Syn.: breathing].
Polyculture: The farming of at least two non- Rhizome: Thick and horizontal stem, generally
competitive species in the same unit of far- underground, which emits growths to the
ming. top and of the roots downwards.
Porosity: Free space between the particles or
the lumps ones in the soil. S
Post-larva: Stage which follows that of the larva Scrubbing: In-depth migration of the soluble
immediately and presents some characters substances or colloids in the interstices of
of the juveniles one. the ground.
Pressure loss: The pressure loss is due for Sedentary: Who moves little and remains in his
example to the friction or the shifting habitat.


Selection (genetic): Action to choose the in- Trace element: Metal or metalloid, present in
dividuals presenting interesting properties small quantity (= with the state of trace) in
and use it as breeder. living tissue and necessary to the metabo-
Size, commercial: Minimal size that the orga- lism of these tissues.
nism must reach to have the right to be sold. Traceability: Ability to trace the whole course of
Size, portion: Size of a consumable fish by only a product or an organism since its farming
one person. until its sale.
Slaked lime: Lime paste obtained by addition of Trophic: Who rerers to the nutrition of the or-
water to quicklime. gans and tissues.
Spawning: General term to indicate of ovules, Turbidity: Disturbance or reduction of the pene-
fertilized or in front of being fertilized; also tration of the light in water resulting from the
used for eggs fertilized, as well as very presence of suspended matter, colloidal or
young fish of the same class of recruitment, dissolved, or of the presence of planktonic
generally many. organisms.
Swim bladder: Organ filled with a gas mixture U
rich in oxygen and allowing the stabiliza-
tion of osseous fish in water. This organ is
connected to the esophagus. The cartila- V
ginous fish (group of the selacians like the Vitamin: Substance necessary in very small
rays and the sharks) do not have any. amount for the good development of the
body and its vital functions.
T Vitelline: Nutritive cells, substances or stuc-
Taxonomy: Classification of the fossil and alive tures being used as endogenous food of
organisms according to their evolutionary eggs or larvae.
relations. Vitellus: Total of the nutritive reserves built-in
Tenure: Socially defined agreements, often des- the cytoplasm of an egg.
cribed in terms “of whole of rights” held by
individuals or groups (recognized either le- W
gally, or customary), concerning the rights
of access and the rules of use of grounds or x
resources which are associated there, such
as individual trees, plant species, water or
animals.
Y
Thermocline: Zone of a water level thermically
Z
stratified (e.g sea, lake, reserve of water)
located under the surfacing, where the va- Zoobenthos: Benthic fauna.
riation in temperature increases abruptly (i.e Zooplankton: Microscopic animals living in
where the temperature decreases quickly suspension in the water mass. Animal com-
with the increase depth). A thermocline ponent of the plankton.
constitutes usually an ecological barrier and
its oscillations influence considerably the Zoosanitary: Who deals with animal health.
distribution and the productivity of stocks. Zootechnical: Technological knowledge to en-
sure the success of an animal farming.


Appendix

Contents
• Examples of files
• Table of data
• Some elements of the biology of the species
• Biogeographic data
• File of species


CONTENTS - APPENDIx
Appendix 01 - ExAMPLES OF FILES 189
I. FILES FOR MONITORING THE PONDS 189
II. FILES FOR THE FOLLOW-UP OF THE FISH 191

Appendix 02 - TABLE OF DATA 193

Appendix 03 - SOME ELEMENTS OF THE BIOLOGY OF THE SPECIES 207
I. THE MORPHOLOGY AND THE SYSTEMATIC 207
II. THE BIOLOGY OF CICHLIDAE 216
II.1. The taxonomy 216
II.2. The feeding habits 217
II.3. The reproduction and parental care 218
III. THE BIOLOGY OF SILURIFORMES OR CATFISH 226
III.1. The Clariidae 226
III.2. The Claroteidae and Auchenoglanididae 231
III.3. The Schilbeidae 233
III.4. The Mochokidae 233
IV. THE OTHER FAMILIES 234
IV.1. The Cyprinidae 234
IV.2. The Citharinidae 234
IV.3. The Distichodontidae 236
IV.4. The Channidae 236
IV.5. The Latidae 237
IV.6. The Arapaimidae 237

Appendix 04 - BIOGEOGRAPHIC DATA 239

Appendix 05 - FILE OF SPECIES 255

Cover photo:
Ö Cichlidae, Hemichromis fasciatus in the wild, Liberia, ASUR, 2006 - © Yves Fermon, Claire Gsegner


Appendix 01
ExAMPLES OF FILES
Are given here some models of:
1. Files to monitor ponds as a whole. These files can be used for all ponds, or separately for
each pond. It will then be enough to make a synthesis of the individual record files of the
ponds.
2. Files for the follow-up of fish. Again, this can be done by species, pond, for all the ponds…

These are examples and should be changed according to the operation implementation.
There is, however, the information necessary for proper management of ponds and fish stocks.

I. FILES FOR MONITORING THE PONDS
Daily fish per pond
Pond n° Month Year

Money Dead Fish given Fish sold
Date Activities and remarks
spent fish Workers Family Quantity Income

Total of the month


Annual balance per pond
Pond n° Years
Money Dead Fish given Fish sold
Month
spent fish To workers To family Total Quantity Income

January
February
March
April
May
June
July
August
September
October
November
December
Total

9 Date: Date of the observation;
9 Activities and remarks: The activities made on the ponds (Feeding, cleaning the dikes…) and
the remarks (water colour, flow…);
9 Money spent: Money spent for one activity (manpower…)
9 Dead fish: Number, weight, species of dead and removed fish;
9 Given fish: Fish given to the workers of for familial consumption;
9 Sales fish: Fish sold at the market or at the exterior to obtain money.

At the end of the year or at the end of the cycle, then it is possible to make a general assess-
ment of activities, income and consumption in general, where appropriate, to improve the operating
system for the other cycles.


II. FILES FOR THE FOLLOW-UP OF THE FISH
Here are two types of files to follow-up the fish:
1. The first two correspond to the quantitative aspects of production. They allow to know by
pond and all ponds, the fish production.
2. The third file is by species and fish or batch of fish to estimate growth and evolution of the
relationship weight / size of fish.
All this information will provide elements to improve production for the next cycle (density by
species, additional food, cycle time…).

Fish stock
Date Pond n° Surface or volume (V)
Species

Introduction date Di

End date Df

Duration (days) Df - Di

Initial number Ni

Initial biomass (g) Bi

Initial mean weight (g) Pmi

Initial density Ni / V

Initial mean size (cm) Tmi

Dead fish

Final number Nf

Final biomass (g) Bf

Final mean weight (g) Pmf

Final mean size (cm) Tmf

Total ration (g) RT

Total production (g) Bf - Bi

Conversion rate RT / (Bf - Bi)

Day growth (g) (Pmf - Pmi) / days

Day growth (cm) (Tmf - Tmi) / days

Survival (%) (Nf - Ni) x 100


Evaluation sheet for growth and production
Date

Pond

Surface or volume

Controle n°

Beginning date Di

End date Df

Duration (days) Df - Di

Initial numbers Ni

Initial biomass (g) Bi

Initial mean weight (g) Pmi

Dead fish

Final number Nf

Final biomass (g) Bf

Final mean weight (g) Pmf

Total ration (g) RT

Total production (g) Bf - Bi

Conversion rate RT / (Bf - Bi)

Day growth (g) (Pmf - Pmi) / jours

Survival (%) (Nf - Ni) x 100

Monitoring of fish - Size / Weight - individual or mean
Pond n° Date

Standard
Species Nomber Sex Weight (g) Remarks
length (cm)


Appendix 02
TABLES OF DATA

Are presented here ici a series of tables given informations on:

Table XXXVIII. The tonnage of halieutic products by African countries.

Table XXXIX. The checklist of freshwater species which have been the subject of an in-
troduction in Africa.

Table XL. The list of freshwater species introduced by African countries.

Table XLI. The list of freshwater species used for aquaculture in Africa.


TABLE xxxVIII. The tonnage of halieutic products in 2005 per African countries
(FAO, 2006).

Fish, crustaceans, molluscs Aquatic plants
Country
Capture Aquaculture Total Capture Aquaculture Total
South Africa 817608 3142 820750 6619 3000 9619
Algeria 126259 368 F 126627 F - - -
Angola 240000 F - 240000 F - - -
Benin 38035 372 38407 - - -
Botswana 132 - 132 - - -
Burkina Faso 9000 6F 9006 F - - -
Burundi 14000 F 200 F 14200 F - - -
Cameroon 142345 337 142682 - - -
Central African Republic 15000 F 0 15000 F - - -
Congo 58368 80 58448 - - -
Congo DR / Zaïre 220000 F 2965 F 222965 F - - -
Côte d’Ivoire 55000 F 866 F 55866 F - - -
Djibouti 260 F - 260 F - - -
Egypt 349553 539748 889301 - - -
Erythrea 4027 - 4027 - - -
Ethiopia 9450 0 9450 - - -
Gabon 43863 78 43941 - - -
Gambia 32000 F 0 32000 F - - -
Ghana 392274 1154 393428 - - -
Guinea 96571 F 0 96571 F - - -
Equatorial Guinea 3500 F - 4027 - - -
Guinea-Bissau 6200 F - 6200 F - - -
Kenya 148124 1047 149171 - - -
Lesotho 45 1 46 - - -
Liberia 10000 F 0 10000 F - - -
Libya 46073 F 266 F 46339 F - - -
Madagascar 136400 8500 F 144900 F - - -
Malawi 58783 812 59595 - - -
Mali 100000 F 1008 F 101008 F - 90 F 90 F
Morocco 932704 2257 934961 12813 - 12813
Mauritania 247577 - 247577 - - -
Mozambique 42473 1222 43695 - 56 56
Namibia 552695 50 F 552745 F 0 67 F 67 F
Niger 50018 40 50058 - - -
Nigeria 523182 56355 579537 - - -
Uganda 416758 10817 427575 - - -
Rwanda 7800 F 386 F 8186 F - - -
Senegal 405070 193 F 405263 F 0 1 1
Sierra Leone 145993 0 145993 - - -
Somalia 30000 F - 30000 F - - -
Sudan 62000 1600 F 63600 F 0 - 0
Swaziland 70 F 0 70 F - - -
Tanzania 347800 F 11 F 347811 F 240 F 6000 F 6240 F
Chad 70000 F - 70000 F - - -
Togo 27732 1535 29267 - - -
Tunisia 109117 2665 111782 - - -
Zambia 65000 F 5125 F 70125 F - - -
Zimbabwe 13000 F 2452 15452 F - - -
Total 93253346 48149792 141403138 1305803 14789972 16095775


TABLE xxxIx. The checklist of freshwater species which have been the subject
of an introduction in Africa (FAO, 2006; Fishbase, 2006).
Environment (E): Found in: m = marines, s = brackish
Maximal size (T): SL = Standard Length - FL = Fork Length - TL = Total Length;
m = male; f = female; ns = non sex
Aquaculture (A): 1 = used for consumption

Order Family Species Author E T A

Osteoglossiformes
(Bony tongues) Arapaimidae Heterotis niloticus (Cuvier, 1829) 100 SL m 1

Anguilliformes
(Eels) Anguillidae Anguilla anguilla (Linnaeus, 1758) m-s 200 TL ns 1
Clupeiformes 17.5 TL
(Herrings, sardines) Clupeidae Limnothrissa miodon (Boulenger, 1906)
ns
Cypriniformes Cyprinidae Aristichthys nobilis (Richardson, 1845) 146 SL ns
(Carps, minnows) Barbus anoplus Weber, 1897 s 10.1 FL f
Barbus barbus (Linnaeus, 1758) 90 SL ns
Carassius auratus auratus (Linnaeus, 1758) 41 TL ns 1
Carassius carassius (Linnaeus, 1758) 64 TL ns 1
Catla catla (Hamilton, 1822) 120 TL ns
Ctenopharyngodon idella (Valenciennes, 1844) 150 TL ns 1
Cyprinus carpio carpio Linnaeus, 1758 120 SL ns 1
Gobio gobio gobio (Linnaeus, 1758) s 13 SL ns
Hypophthalmichthys molitrix (Valenciennes, 1844) 100 TL ns 1
Labeo rohita (Hamilton, 1822) 96 TL ns
Labeobarbus aeneus (Burchell, 1822) 50 FL m
Labeobarbus natalensis (Castelnau, 1861) 68.3 TL m
Mylopharyngodon piceus (Richardson, 1846) 180 SL ns
Rutilus rubilio (Bonaparte, 1837) 25.8 FL f
Rutilus rutilus (Linnaeus, 1758) 45 SL ns
Scardinius erythrophthalmus (Linnaeus, 1758) s 35 SL ns 1
Tanichthys albonubes Lin, 1932 2.2 SL ns
Tinca tinca (Linnaeus, 1758) s 64 TL ns
Characiformes Citharinidae Distichodus niloticus (Hasselquist, 1762) s 83 TL m
(Tétra) Characidae Astyanax orthodus Eigenmann, 1907 10 TL m
Siluriformes Bagridae Bagrus meridionalis Günther, 1894 97 TL f
(Catfish) Schilbeidae Schilbe mystus (Linnaeus, 1758) s 34 SL ns
Clariidae Clarias gariepinus (Burchell, 1822) 150 SL ns 1
Ictaluridae Ictalurus punctatus (Rafinesque, 1818) 100 SL ns
Siluridae Silurus glanis Linnaeus, 1758 500 TL ns 1
Salmoniformes Salmonidae Hucho hucho (Linnaeus, 1758) 165 SL ns
(Salmons) Oncorhynchus mykiss (Walbaum, 1792) m-s 100 SL ns 1
Salvelinus fontinalis (Mitchill, 1814) 85 SL ns
Salmo trutta fario Linnaeus, 1758 60 TL ns
Salmo trutta trutta Linnaeus, 1758 140 TL ns 1
Esociformes
(Pikes) Esocidae Esox lucius Linnaeus, 1758 s 150 TL ns 1

Cyprinodontiformes Aplocheilidae Pachypanchax playfairii (Günther, 1866) s 10 SL m
(Killis, mosquito fish) Cyprinodontidae Aphanius fasciatus (Valenciennes, 1821) m-s 6 SL ns
Poeciliidae Gambusia affinis (Baird & Girard, 1853) s 4.2 SL ns
Gambusia holbrooki Girard, 1859 s 6 SL f
Phalloceros caudimaculatus (Hensel, 1868) 5.2 TL ns
Poecilia latipinna (Lesueur, 1821) 12 SL ns
Poecilia reticulata Peters, 1859 s 5 SL f
14 TL m
Xiphophorus hellerii Heckel, 1848 s
16 TL f
Xiphophorus maculatus (Günther, 1866) 4 SL m


TABLE xxxIx (next). The checklist of freshwater species which have been the
subject of an introduction in Africa (FAO, 2006; Fishbase, 2006).
Environment (E): Found in: m = marines, s = brackish
Maximal size (T): SL = Standard Length - FL = Fork Length - TL = Total Length;
m = male; f = female; ns = non sex
Aquaculture (A): 1 = used for consumption

Order Family Species Author E T A
Perciformes Moronidae Morone saxatilis (Walbaum, 1792) 200 TL m
(Perch, gobies) Terapontidae Terapon puta Cuvier, 1829 m-s 30 TL ns 1
Latidae Lates niloticus (Linnaeus, 1758) s 200 TL m 1
Centrarchidae Lepomis cyanellus Rafinesque, 1819 31 TL m
Lepomis gibbosus (Linnaeus, 1758) 32 SL ns
Lepomis macrochirus Rafinesque, 1819 41 TL m
Lepomis microlophus (Günther, 1859) 43.2 TL m
Micropterus dolomieu Lacepède, 1802 69 TL m
Micropterus punctulatus (Rafinesque, 1819) 63.5 TL m
Micropterus salmoides (Lacepède, 1802) 65 SL ns 1
Percidae Perca fluviatilis Linnaeus, 1758 s 60 SL ns
Sander lucioperca (Linnaeus, 1758) s 130 TL ns 1
Cichlidae Amatitiana nigrofasciata (Günther, 1867) 10 SL
Astatoreochromis alluaudi Pellegrin, 1904 19 SL ns
Astronotus ocellatus (Agassiz, 1831) 45.7 TL m
Oreochromis andersonii (Castelnau, 1861) s 61 TL m 1
Oreochromis aureus (Steindachner, 1864) s 45.7 TL m 1
Oreochromis esculentus (Graham, 1928) 50 SL m
Oreochromis karongae (Trewavas, 1941) 38 SL ns 1
Oreochromis leucostictus (Trewavas, 1933) 32 TL ns
Oreochromis macrochir (Boulenger, 1912) 40.2 TL m 1
Oreochromis mortimeri (Trewavas, 1966) 48 TL ns
Oreochromis mossambicus (Peters, 1852) s 39 TLns 1
Oreochromis niloticus eduardianus (Boulenger, 1912) 49 TL ns
Oreochromis niloticus niloticus (Linnaeus, 1758) s 64 TL ns 1
Oreochromis shiranus shiranus Boulenger, 1897 s 39 SL ns 1
32 SL m
Oreochromis spilurus niger Günther, 1894
29 SL f
19.2 SL m
Oreochromis spilurus spilurus (Günther, 1894) s
16.3 SL f
Oreochromis urolepis hornorum (Trewavas, 1966) s 24 SL m
Serranochromis robustus jallae (Boulenger, 1896) 39.6 SL m
Serranochromis robustus robustus (Günther, 1864) 56 TL m 1
Tilapia guinasana Trewavas, 1936 14 TL m
Tilapia rendalli (Boulenger, 1897) s 45 TL ns 1
Tilapia sparrmanii Smith, 1840 23.5 TL m
Tilapia zillii (Gervais, 1848) s 27 SL ns 1
Eleotridae Butis koilomatodon (Bleeker, 1849) m-s 10.7 TL m
Anabantidae Microctenopoma ansorgii (Boulenger, 1912) 8 TL m
Osphronemidae Macropodus opercularis (Linnaeus, 1758) 5.3 SL ns
Osphronemus goramy Lacepède, 1801 70 SL m
Trichogaster trichopterus (Pallas, 1770) 15 SL m
Channidae Channa striata (Bloch, 1793) 91.5 ns
Channa maculata (Lacepède, 1801) 25 SL ns
Lepidosireniformes Protopterus aethiopicus
(Lung fish) Protopteridae aethiopicus Heckel, 1851 200 TL ns


TABLE xL. List of species introduced by African countries.
N = native (if the number is null, the species is coming from another continent)
I = introduce - E = endemic
o = introduce but not established - q = to be verified

Central Africa
Burkina Faso

Côte d’Ivoire
Country

South Africa

Cape Verde
Cameroon

Congo DR
Botswana

Comoros
Family

Erythrea
Ethiopia
Burundi

Djibouti
Angola
Algeria

Congo

Egypt
Benin
Species

Arapaimidae Heterotis niloticus N N N I I I N
Anguillidae Anguilla anguilla N o
Clupeidae Limnothrissa miodon N NI
Cyprinidae Aristichthys nobilis I o
Barbus anoplus N
Barbus barbus
Carassius auratus auratus I I
Carassius carassius I
Catla catla
Ctenopharyngodon idella I I I I I
Cyprinus carpio carpio I o I I I I I I
Gobio gobio gobio
Hypophthalmichthys molitrix I I o I
Labeo rohita
Labeobarbus aeneus N
Labeobarbus natalensis N
Mylopharyngodon piceus
Rutilus rubilio
Rutilus rutilus
Scardinius erythrophthalmus
Tanichthys albonubes
Tinca tinca I
Citharinidae Distichodus niloticus N I N N
Characidae Astyanax orthodus
Bagridae Bagrus meridionalis
Schilbeidae Schilbe mystus N N N N I N N N
Clariidae Clarias gariepinus N N N N N N N I N N N N
Ictaluridae Ictalurus punctatus
Siluridae Silurus glanis I
Salmonidae Hucho hucho
Oncorhynchus mykiss I I I
Salmo trutta fario I
Salmo trutta trutta I I
Salvelinus fontinalis o
Esocidae Esox lucius I I
Aplocheilidae Pachypanchax playfairii
Cyprinodontidae Aphanius fasciatus N N
Poeciliidae Gambusia affinis I I I I I
Gambusia holbrooki I
Phalloceros caudimaculatus
Poecilia latipinna
Poecilia reticulata I I
Xiphophorus hellerii I
Xiphophorus maculatus


TABLE xL (next ). List of species introduced by African countries.

Central Africa
Burkina Faso

Côte d’Ivoire
Country

South Africa

Cape Verde
Cameroon

Congo DR
Botswana

Comoros
Family

Erythrea
Ethiopia
Burundi

Djibouti
Angola
Algeria

Congo

Egypt
Benin
Species

Moronidae Morone saxatilis I
Terapontidae Terapon puta I
Latidae Lates niloticus N N I N N N
Centrarchidae Lepomis cyanellus I I
Lepomis gibbosus I
Lepomis macrochirus I I
Lepomis microlophus
Micropterus dolomieu I
Micropterus punctulatus I
Micropterus salmoides I I I o o o
Percidae Perca fluviatilis I
Sander lucioperca I
Cichlidae Amatitiana nigrofasciata
Astatoreochromis alluaudi I I I I
Astronotus ocellatus I
Oreochromis andersonii I N N I
Oreochromis aureus I N N
Oreochromis esculentus
Oreochromis karongae
Oreochromis leucostictus I N
Oreochromis macrochir o I N o N I I I I o N I I
Oreochromis mortimeri I
Oreochromis mossambicus I I I N I I o I
Oreochromis niloticus eduardianus N N
Oreochromis niloticus niloticus I I I I I I I I
Oreochromis shiranus shiranus
Oreochromis spilurus niger N
Oreochromis spilurus spilurus I N
Oreochromis urolepis hornorum I
Serranochromis robustus jallae I N N N
Serranochromis robustus robustus
Tilapia guinasana I
Tilapia rendalli N N N I N N N I
Tilapia sparrmanii N N N
Tilapia zillii N N N N N N I I
Eleotridae Butis koilomatodon
Anabantidae Microctenopoma ansorgii N N
Osphronemidae Macropodus opercularis
Osphronemus goramy o o
Trichogaster trichopterus
Channidae Channa maculata
Channa striata
Protopteridae Protopterus aethiopicus aethiopicus N N N N
Number of introductions 24 11 1 2 4 1 4 4 0 6 3 12 8 9 0 9 4 11



Guinea Equatorial
Guinée-Bissau
Country

Mozambique
Madagascar

Mauritania
Family

Mauritius
Morocco

Namibia
Lesotho
Gambia

Guinea

Malawi
Gabon

Liberia
Ghana

Kenya
Species

Libya

Mali
Arapaimidae Heterotis niloticus I N N I
Anguillidae Anguilla anguilla I N N
Clupeidae Limnothrissa miodon I
Cyprinidae Aristichthys nobilis I o
Barbus anoplus N I
Barbus barbus I
Carassius auratus auratus I I I
Catla catla I
Ctenopharyngodon idella I I I o
Cyprinus carpio carpio I I I I o I I I I
Gobio gobio gobio I
Hypophthalmichthys molitrix o o I I o
Labeo rohita I I
Labeobarbus aeneus N N
Labeobarbus natalensis
Mylopharyngodon piceus I
Rutilus rubilio
Rutilus rutilus o I
Scardinius erythrophthalmus o I
Tanichthys albonubes I
Tinca tinca o I
Citharinidae Distichodus niloticus N
Characidae Astyanax orthodus I
Bagridae Bagrus meridionalis N N
Schilbeidae Schilbe mystus N N N N N N N
Clariidae Clarias gariepinus I N N N N N N N
Ictaluridae Ictalurus punctatus
Siluridae Silurus glanis
Salmonidae Hucho hucho I
Oncorhynchus mykiss I I I I I o
Salmo trutta fario I I
Salmo trutta trutta I I I I o
Salvelinus fontinalis I o
Esocidae Esox lucius o I
Aplocheilidae Pachypanchax playfairii q
Cyprinodontidae Aphanius fasciatus N I
Poeciliidae Gambusia affinis I I I I I
Gambusia holbrooki I I I
Phalloceros caudimaculatus I
Poecilia latipinna I
Poecilia reticulata I I I I
Xiphophorus hellerii I I I
Xiphophorus maculatus I I


TABLE xL. (next ). List of species introduced by African countries.

Guinea Equatorial
Guinée-Bissau
Country

Mozambique
Madagascar

Mauritania
Family

Mauritius
Morocco

Namibia
Lesotho
Gambia

Guinea

Malawi
Gabon

Liberia
Ghana

Kenya
Species

Libya

Mali
Moronidae Morone saxatilis
Terapontidae Terapon puta N
Latidae Lates niloticus N N NI N N o N
Centrarchidae Lepomis cyanellus q o I I
Lepomis gibbosus I
Lepomis macrochirus q I I I I
Lepomis microlophus I I
Micropterus dolomieu I
Micropterus punctulatus
Micropterus salmoides I I I I I I o I I
Percidae Perca fluviatilis I
Sander lucioperca I
Cichlidae Amatitiana nigrofasciata
Astatoreochromis alluaudi N
Astronotus ocellatus
Oreochromis andersonii I N
Oreochromis aureus o o I N
Oreochromis esculentus N
Oreochromis karongae NI N
Oreochromis leucostictus I
Oreochromis macrochir I I I I I I N
Oreochromis mortimeri q
Oreochromis mossambicus I N I I
Oreochromis niloticus eduardianus I
Oreochromis niloticus niloticus I N I I I
Oreochromis shiranus shiranus o N
Oreochromis spilurus niger N I I
Oreochromis spilurus spilurus N
Oreochromis urolepis hornorum
Serranochromis robustus jallae N N
Serranochromis robustus robustus N N
Tilapia guinasana E
Tilapia rendalli N I I I N
Tilapia sparrmanii I N N N
Tilapia zillii N N N N N I N N I N
Eleotridae Butis koilomatodon N N
Anabantidae Microctenopoma ansorgii I
Osphronemidae Macropodus opercularis I
Osphronemus goramy I I
Trichogaster trichopterus I
Channidae Channa maculata I
Channa striata I I
Protopteridae Protopterus aethiopicus aethiopicus N
Number of introductions 4 0 3 0 0 0 22 4 1 1 35 8 0 25 23 1 7 9


TABLE xL. (next ). List of species introduced by African countries.

Number of introduced
Sao Tome & Principe

Number of native
Country
Family

Sierra Leone
Reunion La

Seychelles

Zimbabwe
Swaziland
Tanzania
Species

Rwanda

Senegal

Somalia
Uganda

Zambia
Nigeria

Tunisia
Sudan

Chad
Niger

Togo
Arapaimidae Heterotis niloticus N N N N I 6 10
Anguillidae Anguilla anguilla 2 3
Clupeidae Limnothrissa miodon I N NI I 5 2
Cyprinidae Aristichthys nobilis 4 0
Barbus anoplus N 1 3
Barbus barbus 1 0
Carassius auratus auratus I I 7 0
Carassius carassius 2 0
Catla catla I 2 0
Ctenopharyngodon idella I I I I I I 15 0
Cyprinus carpio carpio I I I I o I I I I o I 28 0
Gobio gobio gobio 1 0
Hypophthalmichthys molitrix I 10 0
Labeo rohita o I 4 0
Labeobarbus aeneus I 1 3
Labeobarbus natalensis I 1 1
Mylopharyngodon piceus 1 0
Rutilus rubilio I 1 0
Rutilus rutilus 2 0
Scardinius erythrophthalmus I 3 0
Tanichthys albonubes 1 0
Tinca tinca o o I 6 0
Citharinidae Distichodus niloticus N N 1 6
Characidae Astyanax orthodus 1 0
Bagridae Bagrus meridionalis N I 1 3
Schilbeidae Schilbe mystus N N N N N N N N N 1 23
Clariidae Clarias gariepinus N N N N N N N N 2 26
Ictaluridae Ictalurus punctatus I 1 0
Siluridae Silurus glanis I 2 0
Salmonidae Hucho hucho 1 0
Oncorhynchus mykiss I I I I o o I 16 0
Salmo trutta fario 3 0
Salmo trutta trutta I I I 10 0
Salvelinus fontinalis I 4 0
Esocidae Esox lucius I I 6 0
Aplocheilidae Pachypanchax playfairii E I 1 0
Cyprinodontidae Aphanius fasciatus N 1 4
Poeciliidae Gambusia affinis I o I 13 0
Gambusia holbrooki I 5 0
Phalloceros caudimaculatus 1 0
Poecilia latipinna 1 0
Poecilia reticulata I I I I I 11 0
Xiphophorus hellerii I o 6 0
Xiphophorus maculatus I I 4 0



Number of introduced
Sao Tome & Principe

Number of native
Country

Sierra Leone
Family

Reunion La

Seychelles

Zimbabwe
Swaziland
Tanzania
Rwanda
Species

Senegal

Somalia
Uganda

Zambia
Nigeria

Tunisia
Sudan

Chad
Niger

Togo
Moronidae Morone saxatilis 1 0
Terapontidae Terapon puta N N 1 3
Latidae Lates niloticus N NI N N I N 5 14
Centrarchidae Lepomis cyanellus I I o 8 0
Lepomis gibbosus 2 0
Lepomis macrochirus I o I 9 0
Lepomis microlophus 2 0
Micropterus dolomieu o I o o 6 0
Micropterus punctulatus I I 3 0
Micropterus salmoides o I I I I I 21 0
Percidae Perca fluviatilis 2 0
Sander lucioperca I 3 0
Cichlidae Amatitiana nigrofasciata I 1 0
Astatoreochromis alluaudi N N N 4 4
Astronotus ocellatus 1 0
Oreochromis andersonii I o 5 3
Oreochromis aureus N N o N N I o 7 7
Oreochromis esculentus N I NI 2 2
Oreochromis karongae N 1 2
Oreochromis leucostictus N I I 4 2
Oreochromis macrochir I I I I N 20 5
Oreochromis mortimeri N N 1 2
Oreochromis mossambicus I I I I I 15 2
Oreochromis niloticus eduardianus N N I N 2 5
Oreochromis niloticus niloticus I I I N I I I 18 2
Oreochromis shiranus shiranus N 1 2
Oreochromis spilurus niger I 3 2
Oreochromis spilurus spilurus I N N 2 4
Oreochromis urolepis hornorum N N 1 2
Serranochromis robustus jallae I N N 2 7
Serranochromis robustus robustus I N N 1 4
Tilapia guinasana 1 0
Tilapia rendalli N I I N N N 7 12
Tilapia sparrmanii N N N N 1 10
Tilapia zillii N N N N N I N N N 5 22
Eleotridae Butis koilomatodon I N N 1 4
Anabantidae Microctenopoma ansorgii 1 2
Osphronemidae Macropodus opercularis 1 0
Osphronemus goramy o I 6 0
Trichogaster trichopterus I I 3 0
Channidae Channa maculata 1 0
Channa striata 2 0
Protopteridae Protopterus aethiopicus aethiopicus N I N N N 1 9
Number of introductions 0 8 9 10 11 0 0 5 0 0 5 10 16 0 3 12 14 21 381 217


TABLE xLI. List of freshwater fish used in aquaculture by country (FAO, 2006; Fish-
base, 2008).
I = introduce - E = endemic - o = introduce but not established - q = to be verified
A = Commercial production - X = Experimental

Central Africa
Burkina Faso

Côte d’Ivoire
Country

South Africa

Cape Verde
Cameroon

Congo DR
Botswana

Comoros
Family

Erythrea
Ethiopia
Burundi

Gambia
Djibouti
Angola
Algeria

Gabon
Congo

Egypt
Benin
Species

Arapaimidae Heterotis niloticus N N N IA IA IA A N IA A
Anguillidae Anguilla anguilla A N o
Cyprinidae Carassius auratus auratus IA I
Carassius carassius IA
Cirrhinus cirrhosus
Ctenopharyngodon idella I IA I IA I
Cyprinus carpio carpio IA oA I IA I I IA I
Hypophthalmichthys molitrix I I oA I
Scardinius erythrophthalmus
Alestidae Brycinus lateralis N N N N
Bagridae Bagrus bajad N N N N N
Claroteidae Chrysichthys nigrodigitatus N N N A N N
Schilbeidae Schilbe intermedius N N N N N
Clariidae Clarias anguillaris N N A N N A N N
Clarias gariepinus A N N N N N N A A N A I N N N N IA N
Clarias ngamensis N N N
Heterobranchus bidorsalis N N N N N
Heterobranchus longifilis N N N N N N N NX N N N
Siluridae Silurus glanis I
Mochokidae Synodontis nigromaculata N N N N N
Salmonidae Oncorhynchus mykiss IA I I
Salmo trutta trutta I I
Esocidae Esox lucius I I
Mugilidae Liza ramado N N
Mugil cephalus N N N N N N N A N N
Moronidae Dicentrarchus labrax A A
Terapontidae Terapon puta IA
Latidae Lates niloticus N N I N N N
Centrarchidae Micropterus salmoides IA I I o o o
Percidae Sander lucioperca IA
Cichlidae Oreochromis andersonii I N N I
Oreochromis aureus I N A N
Oreochromis karongae
Oreochromis macrochir o I N o N I I I I o N I I I
Oreochromis mossambicus A I I I N I I o I
Oreochromis niloticus niloticus IA I A IA A IA I IA IA A A I IA N
Oreochromis shiranus shiranus
Sargochromis carlottae N N
Sargochromis giardi N N
Sarotherodo galileus galileus N N N N N N N N
Sarotherodon melanotheron melanotheron N N N X N
Serranochromis robustus robustus
Tilapia cameronensis EA
Tilapia rendalli N N N I N N N I N
Tilapia zillii N N N N N N I I N
Number of species used in aquaculture 7 5 0 0 0 2 1 4 0 3 0 2 3 6 0 8 0 1 3 1
Number of species introduced for aquaculture 5 3 0 0 0 0 1 1 0 2 0 2 2 0 0 4 0 1 3 0
Number of species introduced 11 8 1 2 3 1 3 3 0 4 1 6 4 5 0 7 4 10 4 0
Number of species natives 6 4 12 11 11 5 3 14 1 2 1 3 8 6 1 10 1 9 3 10


TABLE xLI (next). List of freshwater fish used in aquaculture by country (FAO,
2006; Fishbase, 2008).

Guinea Equatorial
Guinea-Bissau
Country

Mozambique
Madagascar

Reunion La
Family

Mauritania
Mauritius
Morocco

Namibie
Lesotho

Uganda
Guinea

Malawi

Nigeria
Liberia
Ghana
Species

Kenya

Libya

Niger
Mali
Arapaimidae Heterotis niloticus A A N N IA A N A
Anguillidae Anguilla anguilla I N A N
Cyprinidae Carassius auratus auratus I I I
Cirrhinus cirrhosus A
Ctenopharyngodon idella I IA I oA I IA
Cyprinus carpio carpio I IA IA IA oA IA I IA I I IA IA
Hypophthalmichthys molitrix o o IA I o
Scardinius erythrophthalmus o I
Alestidae Brycinus lateralis N A
Bagridae Bagrus bajad N N N N N
Claroteidae Chrysichthys nigrodigitatus A N N N A A
Schilbeidae Schilbe intermedius N N N N A N
Clariidae Clarias anguillaris A N N N N N
Clarias gariepinus A A N N A A N N A A N N A N A N
Clarias ngamensis N N A
Heterobranchus bidorsalis A N A N N N
Heterobranchus longifilis A N N A N N N N
Siluridae Silurus glanis
Mochokidae Synodontis nigromaculata N A
Salmonidae Oncorhynchus mykiss IA IA IA IA IA o IA
Salmo trutta trutta IA I I I o
Esocidae Esox lucius o IA IA
Mugilidae Liza ramado q N N
Mugil cephalus N N N N N N N N N N N
Moronidae Dicentrarchus labrax A A N
Terapontidae Terapon puta N
Latidae Lates niloticus A N N NI N N o N N A NI
Centrarchidae Micropterus salmoides I I I I IA I o IA I o
Percidae Sander lucioperca I
Cichlidae Oreochromis andersonii I N A
Oreochromis aureus o o I N N N o
Oreochromis karongae NIA N
Oreochromis macrochir IA I IA I I N A
Oreochromis mossambicus I N I A A IA I IA
Oreochromis niloticus niloticus A A IA A I A I A A A A IA
Oreochromis shiranus shiranus o A N
Sargochromis carlottae A
Sargochromis giardi A
Sarotherodo galileus galileus N N N N A N N N N N N
Sarotherodon melanotheron melanotheron A N N N N N
Serranochromis robustus robustus N N
Tilapia cameronensis
Tilapia rendalli I IA A I N A N A I
Tilapia zillii N N N N A I N N I N N N A
Number of species used in aquaculture 10 3 0 0 5 3 6 1 4 7 3 8 1 1 5 11 1 6 4 5
Number of species introduced for aquaculture 1 0 0 0 4 2 1 0 4 3 0 6 0 0 3 1 0 0 2 5
Number of species introduced 2 0 0 0 13 4 1 1 16 5 0 10 10 1 4 4 0 3 5 5
Number of species natives 5 8 2 9 8 1 4 4 1 4 6 4 1 9 13 2 11 9 4 0


TABLE xLI (next). List of freshwater fish used in aquaculture by country (FAO,
2006; Fishbase, 2008).

Number of introduiced
Number of times used
Sao Tome & Principe

Number of times

Number of times
for aquaculture
in aquaculture
Country

introduice

native
Sierra Leone
Family

Seychelles

Zimbabwe
Swaziland
Tanzania
Rwanda

Senegal

Somalia
Species

Zambia
Tunisia
Sudan

Chad
Togo
Arapaimidae Heterotis niloticus N N N I 11 5 6 10
Anguillidae Anguilla anguilla A 3 0 2 3
Cyprinidae Carassius auratus auratus I I 1 1 7 0
Carassius carassius 1 1 2 0
Cirrhinus cirrhosus 1 0 0 0
Ctenopharyngodon idella I I I I 5 5 15 0
Cyprinus carpio carpio IA o IA I I IA oA I 16 16 27 0
Hypophthalmichthys molitrix I 2 2 10 0
Scardinius erythrophthalmus IA 1 1 3 0
Alestidae Brycinus lateralis N N 1 0 0 7
Bagridae Bagrus bajad N A N 1 0 0 12
Claroteidae Chrysichthys nigrodigitatus N N N 4 0 0 11
Schilbeidae Schilbe intermedius N N N N N N N N 1 0 0 18
Clariidae Clarias anguillaris N N N N N 3 0 0 16
Clarias gariepinus A N N N N A A N N A A 18 1 2 26
Clarias ngamensis N N N 1 0 0 8
Heterobranchus bidorsalis N N N N 2 0 0 13
Heterobranchus longifilis N N N N N N N N 3 0 0 24
Siluridae Silurus glanis IA 1 1 2 0
Mochokidae Synodontis nigromaculata N N N 1 0 0 9
Salmonidae Oncorhynchus mykiss I I IA o o IA 9 9 16 0
Salmo trutta trutta I I I 1 1 10 0
Esocidae Esox lucius I 2 2 6 0
Mugilidae Liza ramado A 1 0 0 4
Mugil cephalus N N N N N N A 2 0 0 26
Moronidae Dicentrarchus labrax N A 5 0 0 2
Terapontidae Terapon puta N N 1 1 1 3
Latidae Lates niloticus N N A I N A 4 0 3 16
Centrarchidae Micropterus salmoides I I I I I 3 3 21 0
Percidae Sander lucioperca IA 2 2 3 0
Cichlidae Oreochromis andersonii IA A oA 4 2 5 3
Oreochromis aureus N N I o 1 0 7 7
Oreochromis karongae N 1 1 0 3
Oreochromis macrochir I I IA I A N 5 3 20 5
Oreochromis mossambicus I A I I A 7 2 15 2
Oreochromis niloticus niloticus IA A A A IA N A I IA I 27 11 18 2
Oreochromis shiranus shiranus N 1 0 1 2
Sargochromis carlottae N N 1 0 0 4
Sargochromis giardi N N 1 0 0 4
Sarotherodo galileus galileus N N N N 1 0 0 22
Sarotherodon melanotheron melanotheron A N N 3 0 0 11
Serranochromis robustus robustus IA N N 1 1 1 4
Tilapia cameronensis 1 0 0 1
Tilapia rendalli I N A A N A N 7 1 7 12
Tilapia zillii N N N I N N N 2 0 5 22
Number of species used in aquaculture 0 3 2 0 1 0 3 5 6 0 2 8 6 4 170
Number of species introduced for aquaculture 0 2 0 0 0 0 0 2 4 0 0 4 2 2 72
Number of species introduced 0 6 0 2 0 0 4 5 11 0 3 10 5 8 215
Number of species natives 1 1 14 1 9 3 8 0 9 13 9 1 8 9 317


Appendix 03
SOME ELEMENTS OF THE BIOLOGY OF THE SPECIES
Some general information of the biology of the some species used in aquaculture is presented
here. The biogeographic aspects were approached in the chapter III p. 21.

I. THE MORPHOLOGY AND THE SYSTEMATIC
The morphology of fish is one of the elements which allow to determine them. It is very variable
and is to be connected to the way of living, with the behaviors and habitus. One will find the main
anatomical external terms of a fish on Figure 152 below. Will be given here the morphological cha-
racters allowing to distinguish the various species. The drawings and part of the text come from the
Fauna of the freshwater and brackish fish of West Africa (IRD, 2004).
Dorsal fin
Back
Lateral line

Opercle
Caudal peduncle

Head

Chin
Thoat
Caudal fin
Chest Belly
Anal fin
Pectoral fins
Pelvic fins

Figure 152. Principal terms pertinent to the external morphology of a fish.

9 Ratio body length/body depth ( (L/H) (Figure 153 below)

Anguilliform, Serpentiform Strongly elongate Elongate
L / H = 12 - 18 L / H = 7 - 10 L / H = 4 - 6

Short or medium Deep Very deep
L / H = 3 - 4 L / H = 2 - 3 L / H < 2

Figure 153. Different body shapes.


9 Body shape in cross-section (Figure 154 ci-dessous)

A B C D
Figure 154. Cross-section of body. A: Laterally compressed; B: More or less rounded; C: Dor-
so-ventrally depressed; D: Strongly depressed or dorso-ventrally flattened.

9 The head
¾ The jaws (Figure 143 below)
The premaxilla(e), the maxilla(e) and in certain families, the supramaxilla(e) of the upper jaw are
normally distinguished from the mandible(s) of the lower jaw (A). Depending on species or families,
the jaws may be equally long and normally developed (Alestidae, certain Cyprinidae) (B) or strongly
elongate, forming a beak (rostrum) (Belonidae) (C); In both cases, the mouth is called «terminal». The
jaws may also be unequal, the mouth then being either superior (Cyprinodontidae, Centropomidae)
(D), subinferior (certain Mormyridae) (E) or inferior (Mochokidae (F). Finally, some species have a
protrusible or protractile mouth (Serranidae, Gerreidae) (G). In certain genera, e.g., Labeo , Garra
and Chiloglanis , the mouth has strongly developed lips sometimes forming (e.g., in Chiloglanis ) a
sucking disk (H) which allows the fish to cling to rocks and live in rather turbulent waters.

pmx

mx E G
md
C
A Retracted

Protrused

B H
D F

Figure 155. Jaws. A: Premaxilla (pmx), maxilla (mx), mandible (md); B: Jaws equal, prolonged
into a beak; C: Jaws equal, normally developed; D: Mouth superior;
E: Mouth subinferior; F: Mouth protrusible; G: Mouth inferior;
H: Mouth inferior, forming a sucking disk.


¾ Les dents (Figure 156 ci-dessous)
These are inserted on the rim of the jaws, i.e., premaxilla, maxilla, and dentary (mandibular bone),
on the longitudinal axis of the roof of mouth (vomer and parasphaenoid(s), on both sides of the
mouth roof (palatines and ectopterygoids), and on the upper and lower pharyngeal bones. Finally,
certain species have lingual teeth. Evidently, not all of these types of teeth are always present. The
different kinds of teeth are distinguished here by the number of cusps they bear.
Thus, there are: monocuspid teeth that may be straight (certain Marcusenius species) (A), conical
or caniniform (certain Alestidae and Cichlidae) (B and C), cutting (Hydrocynus species, Sphyraeni-
dae) (D) or recurved (Synodontis species) (E); bicuspid teeth (Petrocephalus , Distichodus) (F and G);
polycuspid teeth with cusps set in a single plane (certain Alestidae and Cichlidae) (H), and molari-
form polycuspid teeth with cusps forming a crown (certain Alestidae) (I). There are also other, less
common kinds of teeth.

A B C F G

D E H I
Figure 156. Tooth shapes.
Monocuspid straight (A: Marcusenius sp.), conical (B: Brycinus sp. and C: Chromidotilapia
sp.), cutting (D: Hydrocynus sp.) and recurved (E: Synodontis sp.).
Bicuspid (F: Petrocephalus sp. and G: Distichodus sp.).
Polycuspid in one plan (H: Micralestes sp.) and molariform (I: Brycinus sp.).

¾ The eyes
Depending on families, the eyes may be located in different positions. They are usually lateral,
but may be placed dorsally, particularly in the Batoidea and the Pleuronectiformes (where they are
furthermore both located on the same side of the head). Finally, they may be protruding as in Pe-
riophthalmus. In some species, the eyes are partially covered by an adipose eyelid, a nictitating fold
or a nictitating membrane.
1 2
¾ The fontanellae
(Figure 157 opposite)
The cranial fontanellae are
sometimes used as a genus- or
species-diagnostic criterion for
identification; the fronto-parietal
fontanellae in some Alestidae (A),
and the frontal and occipital fonta-
nellae in some Clariidae (B). A B

Figure 157. Fontanellae. A: Alestes sp.;
B: Clarias sp.: frontal (1) and occipital (2).


¾ The barbels (Figure 158 below)
there may be three types of barbels. A pair of nasal barbels just behind the posterior nostrils (Ba-
gridae, Clariidae) (A); a pair of maxillary barbels provided with a basal membrane (some Mochokidae)
(B), or without basal membrane (some Cyprinidae and Mochokidae); and one (some Cyprinidae) or
two (Siluriformes) pairs of mandibular barbels. In certain groups, the maxillary (some Synodontis) and
mandibular (all Synodontis) may be branched (C). Finally, the mandibular barbels may be sometimes
enclosed in the lips as in Chiloglanis (D).

1

4

2
A 3 B C D

Figure 158. Barbels.
A: The types: Nasal (1), maxillary (2), outer mandibular (3) and inner (4).
B: Membranous maxillary barbels (Synodontis sp.);
C: Branched maxillary barbels (Synodontis sp.);
D: Mandibular barbels enclosed in the lips (Chiloglanis sp.).

¾ The gill cover
A bony lid that covers the gill slits in the Osteichthyes. Depending on the group, the branchios-
tegal membrane that covers the opercular bone may or not be fused to the isthmus of the throat.
This is used as an identification criterion in certain Siluriformes. In most cases it is widely open, but
in some others, the aperture may be rather small, or strongly reduced. In the Chondrichthyes, the gill
slits are not covered by an opercle.

¾ The gill arch (Figure 159 below)
It is formed by three bones bearing externally the gill filaments and internally, the gill rakers. The
upper bone is the epibranchial, the lower ones are the ceratobranchial and the hypobranchial (E). In
some species (Polypteridae), the juveniles have
a pair of external gills (F) which are later reab- 3 4
sorbed. This is also the case in the embryos of 1
2
Protopterus, which have three or four pairs of
external gills.
A
B
¾ Accessory aerial breathing organs
(Figure 160, p. 211)
Some forms have the possibility, thanks to
the possession of specialized organs, to survive
for some time outside the water without suffe-
C
ring major damage. There are several types of
such organs: the branched organ of the Clarii-
dae (A), the lungs of the Protopteridae and Po-
lypteridae (B), the labyrinthiform organ of the Figure 159. Gill slits without opercule (A:
Anabantidae (C), the pharyngeal diverticulum of Sharks); gill arch formed by: ceratobranchial
the Channidae (D), the swim bladder of Gymnar- (1), gill rakers (2), hypobranchial and epibran-
chus (E) and Heterotis. chial (3), gill filaments (4) (B); external gill of a
young Polypterus sp. (C).


2 3 2
1

4
A 3 1
2
3 1 2
2
B1 1
1 3
B2 C D E
3 4

Figure 160. Accessory aerial breathing organs. Branched breathing organs (A: Clarias sp.),
branches (1), gills (2), branchial valves (3); position of the swim bladder (1) and the lungs (2
and 3; plates of the labyrinth in an Anabantidae (C), principal plates (1-3), stylet (4); pharyn-
geal diverticula (D: Parachanna sp.), anterior chamber (1), posterior chamber (2), communi-
cation with pharynx (3); digestive tract and swim bladder (E: Gymnarchus sp.), swim bladder
(1), opening of pneumatic duct (2).

9 The body
The forms and constitutions of fins, the types of scales and other features make possible to
diferenciate species.
¾ The fins
The fins may be paired (pelvics or ventrals and pectorals) that are equivalent to the members of
Tetrapods or unpaired (dorsal, caudal and anal):
The paired fins are the pelvics (ventrals) and the pectorals (Figure 161 below).
In the Gobiidae, the pelvics are either fused into a ventral disk (A), or united by a transverse mem-
brane. In Periophthalmus, they are also united, while the pectorals allow these fishes to move rather
quickly on dry land. In the Siluriformes, the first pectoral-fin ray is often ossified, forming a spine that
may be denticulate on one or both margins (B). In the Polypteridae, the pectoral fins are real paddles
attached to the trunk by a peduncle (C) that allow the fish to effect a wide range of movements.

A B C
Figure 161. Pair fins. Coalesced pair of pelvic fins in a Gobiid species (A);
first pectoral-fin ray denticulated on one margin (1) or on both margins (2) (B: Clarias sp.);
paddle-shaped pectoral fin (C: Polypterus sp.).

The unpaired fin are the dorsal, caudal and anal fins.
there are three types of dorsal fin (Figure 162, p. 212): one is supported by simple spinous rays,
another with soft, usually branched, rays, and the so-called adipose dorsal fin. The latter is usually
placed behind the soft-rayed dorsal (A). Many fishes have two dorsal fins, the first spinous (anterior)
and the second soft; or a single dorsal fin with anterior spinous rays followed by soft rays (B). In some
species (the majority of Siluriformes), the first ray is represented by a strong, more or less denticulate,
spine. Depending on species, the dorsal fin may have different shapes, i.e., outer margin straight,
concave or rounded, filamentous. (C). Finally, some species lack dorsal fins (certain Schilbeidae).


1 2
B

3 A 4 1 C 1
Figure 162. Dorsal fin. Soft dorsal (2) preceded by a strong spinous ray (1) and followed by
an adipose dorsal (3) (A). Two dorsal fins: spiny rays (1), and simple or branched rays (2),
separate (B1) and contiguous (B2). Fin margin straight (1), concave (2), rounded (3) and fila-
mentous (4) (C).

Depending on the relative length of its upper and lower lobes, the caudal fin is termed (Figure
163 below) homocercal, when the lobes are symmetrical (A); heterocercal: when the lobes are ex-
ternally and internally asymmetrical, with either the upper (Carcharhinidae) (B1), or the lower lobe
(some Amphiliidae) (B2) better developed. The shape of the caudal fin may vary with species from
rounded to forked, notched, emarginate. (C): In the Cyprinodontidae, caudal-fin shapes are manifold.

A B1 B2

1 2 3 4 5 6 7
C
Figure 163. Caudal fin.
Homocercal (A: Citharinus sp.). Heterocercal (B1: Carcharhinus sp.) and (B2: Amphiliidae).
Caudal shapes (C): rounded (1), truncate or emarginate (2), concave (3),
lunate (4), forked (5), pointed and separated from dorsal and anal fins (6),
absent or coalesced with dorsal and anal fins (7).

The morphological diversity of the anal fin may be used for the identification of certain species,
especially within the Cyprinodontidae. In some Alestidae, its shape differs between males and adult
females. In the Perciformes, the first simple rays are modified into real spines. In some Siluriformes
(Schilbeidae, Clariidae), this fin is very well developed while in other families (Gymnarchidae), it is
absent.


¾ The scales
Two principal types of scales can be distinguished on the basis of their structure (Figure 164 be-
low). The first of these groups is represented by the ganoid scales, characteristic of the Polypteridae,
which are thick and rhombic and covered by a shiny outer layer of ganoine (A). The second group
comprises two different kinds: the cycloid scales which are thin and smooth (Clupeidae, Alestidae)
(B); and the ctenoid scales which bear small spines on their posterior margin (Distichodontidae, Lut-
janidae) (C). In the Tetraodontidae, the scales are modified into spicules (D), and in the Syngnathidae
they are modified into bony plates separated by areas of naked skin (sutures). The Siluriformes lack
scales altogether, except certain Amphiliidae which have bony plates covering the body. Finally, in
the Chondrichthyes there are the so-called placoid scales which can be considered as small teeth,
also called dermal denticles, which give the skin of these fishes a particularly rough surface (E). In
some families there is a midventral crest formed by hardened scales appearing as shields (scutes),
i.e., in the Clupeidae (F).

A B C D E
Figure 164. Different types of scales. A: Ganoid; B: Cycloid; C: Ctenoid;
D: Dermic sclerification in Tetraodontidae; E: Placoid (denticules).
¾ The lateral line (Figure 165 below)
In scaled fishes, this line is communicated with the surrounding water by a longitudinal series
of pores which frequently open on the pored lateral-line scales. There are four types of lateral lines:
complete, with perforations on all lateral-line scales (Mormyridae and some Alestidae) (A); interrup-
ted, with pored scales on two levels (Cichlidae, Anabantidae) (B); incomplete, with only the anterior
scales perforated (some Alestidae and Mugilidae) (C), and absent (some Mugilidae and Nandidae).

A B C
Figure 165. Lateral line. A: Complete; B: Interrupted on two levels; C: Incomplete.

¾ Electric organs
Some families have electric organs variable in shape, power and function, located in different
parts of the body. The electric organs of the Gymnarchus species, as well as those of the Family
Mormyridae, produce rather weak discharges and seem to serve mainly for the recognition of conge-
ners and obstacles (A and B). Those of the Malapterurus species are capable of much stronger
discharges and are used for purposes of defence and attack (C).

A B C
Figure 166. Location of electric organs. Gymnarchus (A); Mormyridae (B); Malapterurus (C).
The arrows indicate the direction and sense of the electric current inside the organs.
The plane is that of the electric plates.


9 Principal measurements and counts
These measures are important to determine the species but also to monitor the fish in a pond.
The measurements are presented Figure 153 p. 175. The numbers in parentheses correspond to
those indicated on the figures.

¾ Total length (1): horizontal distance from front tip of snout to hind tip of caudal fin.
¾ Standard length (2): horizontal distance from front tip of snout to base (or articulation) of caudal
fin.
¾ Body depth (3): maximum vertical depth of fish, excluding fins.
¾ Head length (4): depending on families, either the horizontal distance from front tip of snout to
hind margin of gill cover, or the horizontal distance from front tip of snout to hind tip of occiput or
to the bony rim of the notch formed by the scapular girdle behind the head.
¾ Snout length (5): horizontal distance from front tip of upper jaw to anterior margin of eye.
¾ Eye diameter (6): horizontal diameter of eye.
¾ Interorbital width: minimum width between the orbits.
¾ Predorsal length (7): horizontal distance from front tip of snout to the articulation of first dorsal-
fin ray.
¾ Preanal length (8): horizontal distance from front tip of snout to the articulation of first anal-fin
ray.
¾ Prepectoral length (9): horizontal distance from front tip of snout to the articulation of first pec-
toral-fin ray.
¾ Prepelvic (preventral) length (10): horizontal distance from front tip of snout to the articulation
of first pelvic (ventral) - fin ray.
¾ Length of dorsal-fin base (11): maximal horizontal distance measured between both ends.
¾ Length of anal-fin base (12): see dorsal-fin base.
¾ Pectoral-fin length (13): length from articulation of first ray to tip of longest ray.
¾ Pelvic (ventral)-fin length (14): see pectoral-fin length.
¾ Caudal-peduncle length (15): horizontal distance from hind margin of anal fin (or from that of
dorsal fin if this extends further backwards than anal) to base of caudal fin.
¾ Depth of caudal peduncle (16): minimum vertical depth of caudal peduncle.

One proceed also to a number of counts.
¾ Fin formula: the number of spines or simple rays in Roman numerals and that of soft bifurcate
(branched) rays, in Arabic numerals (example: III-7).
¾ Number of scales in lateral line and/or in a longitudinal series.
¾ Number of scales on a transverse series.
¾ Number of predorsal scales.
¾ Number of scales around caudal peduncle.
¾ Number of gill rakers on first gill arch.
¾ Number of teeth in the outer and inner rows of upper and lower jaws.

Ö All these features are important to determine which family, genus, species are far-
med species.


1
4
2
7 11
6
5
15

3 16 A

13
9 12
14

10
8

1
2
74
11

6 13 15
5 16
3
B
14

9
12
10

8
7
11 15
5 4

3 16 C

6
14
9
10
8 12
2
1

Figure 167. Principal measurements that may be taken on a fish. A: Characiforme; B: Perci-
forme; C: Siluriforme. For explanation of numbers, please refer to text.


II. THE BIOLOGY OF CICHLIDAE
This perciform freshwater family fish, which occasionally occurs also in brackish waters, is dis-
tributed predominantly in tropical areas of America and Africa, but also in Asia minor, tropical Asia,
Madagascar and Sri Lanka. The Cichlidae have a single nostril on either side of head (Figure 168
below). Body shape variable, but never very elongate, more or less compressed and covered with
cycloid or ctenoid scales. All fins are present. Lower pharyngeal bones fused together, forming a
toothed triangle. The reader may find several files on Cichlidae species in Appendix 05 p. 255.
The family is very widely distributed in Africa, where some of the species are of great interest
to fish culture. Over a hundred genera have been described for that continent. As was seen before
(Chapter 03, paragraph II, p. 21), three genera represent the main species for African aquaculture.
Other species, predators, are used for the control of reproduction.

2

1 1
* 3 *
* 3

A B
+ *
* *

Figure 168. External features of the Cichlidae. A: Tilapia zillii; B: Haplochromis spp.
Family characteristics: 1: A single pair of nostril; 2: Dorsal fin in two continuous parts, hard
and soft rays; 3: Lateral line interrupted.
Intra-family characteristics: +: Tilapiine mark well visible in juveniles;
*: Cycloid scales; **: Ctenoid scales.

II.1. THE TAxONOMY
We can generally separate the Tilapiines from the other African Cichlidae by the presence of the
tilapiine mark on the dorsal fin, well visible in juveniles, and by the cycloids scales (Figure 154 above).
Trewavas (1983) has subdivised the tilapia sensu lato in three main genera, Sarotherodon, Oreo-
chromis and Tilapia sensu stricto. One of the criteria of differentiation was the mode of reproduction.
Sometimes in conjunction, other criteria were used.
9 The genus Tilapia comprises exclusively species that attach their eggs to the substrate,
unlike all others, which are mouth-breeders. Apart from this ethological character, the Tilapia species
differ from those in the other two genera by the following features: lower pharyngeal bone as long as
broad and with an anterior part shorter than the toothed part; posterior pharyngeal teeth bicuspid or
tricuspid (sometimes quadricuspid) and lower limb of first gill arch with at most 17 gill rakers (against
28 in the other genera).
9 Most species of Oreochromis have been described under the genus Tilapia. On the basis
of ethological characters, Trewavas (1983) has included in this genus all species in which mouth
breeding is practised exclusively by females. Other diagnostic features of the genus Oreochromis are
the small size of scales on belly as compared to those on sides; the genital papilla, well developed
in both sexes, the shape of the lower pharyngeal bone (longer than broad or as long as broad, its
toothed part as long as, or somewhat longer, than anterior part); and the posterior pharyngeal teeth


which are either bicuspid, have their lower cusps reduced, or lack distinct cusps altogether.
9 As in the genus Oreochromis, the majority of species placed today in the genus Sarothe-
rodon were originally described under the genus Tilapia. Based on ethological features, Trewavas
(1983) has transferred to the genus Sarotherodon those species in which both, males and females,
practise mouth breeding. Apart from this ethogical character, the genus Sarotherodon is charac-
terized by the following features: scales on belly almost as large as those on sides; genital papilla
smaller in males than in females; lower pharyngeal bone longer than broad, its toothed part shorter
than anterior part; posterior pharyngeal teeth either bicuspid, with a reduced lower cusp, or without
distinct cusps.

II.2. THE FEEDING HABITS
Among the many examples of food diets and the trophic adaptations which are associated, the
most remarkable are those observed at Cichlidae of the African Great Lakes. All the types of food
existing in these lakes were used by these fish and often with morphological adaptations and ade-
quate behaviors. There exists, for example, in the molluscivorous fish, some species are extractors
and others crushing. In the same way, the eaters of epilithic algae have different strategies, some
grazing the algae of the rocks, the others cutting them short-nap. One will note also certain particular
adaptations like the scales eaters and the fish cleaner which feed on parasites of other fish.
The tilapia are, in general, microphagous and/or herbivorous (Table XLII, p. 217 below). However,
as for the large majority of Cichlidae, they are the opportunistic, i.e. they are able to feed on a large
variety of items. For example, Oreochromis niloticus is a phytoplanktonophagous, i.e. which feed
mainly phytoplankton and which can also eat blue algae, zooplankton, sediments rich in bacteria
and diatoms, as well as artificial food.
Tilapia guineensis has an inferior mouth (in low position). Its diet is not specialized with herbivo-
rous tendency, i.e. he eats everything, especially grasses. Sarotherodon melanotheron is a micro-
phagous, planktivorous and benthophagous, i.e. he eats mainly plankton and organizations living at
the bottom (benthos).

Table XLII. Diet of several species of tilapia in natural waters.

Phyto- Zooplan- Macro- Periphy- Inverte- Eggs and
Species Algae Detritus
plankton kton phytes ton brates lavae of fish
O. aureus X X
O. esculentus X
O. jipe X
O. leucostictus X X
O mossambicus X X X X X X X
O. niloticus X
O. pangani X
O. shiranus X X X
O. variabilis X
S. galileus X
S. melanotheron X X X
T. guineensis X X X
T. kottae X X X
T. mariae X X
T. rendalli X X X
T. sparrmanii X
T. zillii X X


II.3. THE REPRODUCTION AND PARENTAL CARE
Cichlidae present elaborate courtship and which are in connection with their parental care. The
mode of care to the fry is one of the criteria of differentiation of the genera of tilapia. There are two
principal for Cichlidae which are enumerated below.
II.3.1. SUBSTRATE SPAWNING
The tilapia practicing this method of reproduction have been placed in the genus Tilapia. A
large part are monogamous. The adhesive eggs are deposited on a hard surface. According to the
species, it can be a hidden substrate (crevices of rock, snail shells), or an open substrate (cups
generally arranged on the muddy sand or movable soil) (Photo W, p. 219), then fertilized. The eggs are
fertilized and hatch after a few days during which the two parents ensure a vigilant guard in general.
When the larvae can swim freely, they remain in group close to the substrate under the monitoring
of the parents.
The eggs are yellowish glue on a stone or piece of wood inside the nest in Tilapia zillii, as shown
in Figure 169 below. The more there are cavities, the more there are spawning. One of the parents
remains constantly above it nest, to supervise the egg laying and the alevins leave the nest when
they reached 8 mm length.

A
B

C D

Figure 169. Courtship and spawning in a substrate
spawner Cichlidae, Tilapia zillii. The female is gray. A and
B: The female deposits a first set of eggs on the subs-
trate cleaned in advance. The male remains nearby;
C: The female leaves the nesting site, the male passes
over the eggs and fertilize them.The A to C sequence is
repeated several times; D: Female, become darker, take
E care and aerates the eggs which have been gathered;
E: The female Tilapia zillii clean eggs.


II.3.2. MOUTHBROODING
The eggs are larger but relatively fewer than at the substrates spawners. Most of the time, the
spawn is carried out on a substrate, often prepared by the male. However, for some pelagic species,
the spawn can take place in full water. In general, they are polygamous species. The males form a
territory which the females come to visit. One distinguishes three main categories of oral incubation:
9 Maternal incubation is the most frequent system. The spawn takes place on a substrate,
and the non-adhesive eggs, laid singy or by small groups, are taken quickly in the mouth by the
female. The male deposits its sperm at the time when the female collects eggs or then fertilizes
them in the mouth. Mouthbrooding continues until the juveniles are entirely independent. In certain
cases, the female release them periodically to feed then takes them in the mouth. It is the case of
all Haplochromines and the genus Oreochromis. The females can incubate at the same time eggs
fertilized by several partners.
9 Paternal incubation is practiced by some species only. It is the case for Sarotherodon
melanotheron.
9 Biparental incubation is also a rare case among Cichlidae. At the majority of Chromidotila-
pines the two parents share the fry. There exist also species at which the female begins incubation
then the male takes over: it is the case of Cichlidae gobies of lake Tanganyika.

At the oral incubators, often, the males stayed on a zone of nesting at a shallow depth and on
a movable substrate (gravel, sand, clay). Each male showing a characteristic color patterns delimits
and defends a territory and arranges a nest, where it will try to attract and retain a ripe female. The
shape and the size of the nest vary according to the species and even according to the popula-
tions within the same species (Figure 170 below). It is often about an arena social organization of
reproduction. The females which live in band near the surface of reproduction come only for briefs
stays on the arenas. Going from one territory to another, they are courted by successive males until
the moment when, stopping above the cup of a nest, they form a transitory couple. After a parade
of sexual synchronization (Figure 171, p. 220), the
female deposits a batch of eggs, the male im-
mediately fertilizes them by injecting its sperm
on eggs in suspension in water, then the female
is turned over and takes them in the mouth to
incubate them. This very short operation can
be started again, either with the same male, or
with another male in a nearby territory. At Haplo-
chromines, the anal fins present a spot mimicry
an egg to lure the females. It is about succes-
sive polygyny and polyandry. Finally, the female
moves away from the arena where the males re-
main confined and carries in mouth the fertilized
eggs which it will incubate in sheltered zones. Photo W. Nests of Tilapia zillii (Liberia)
[© Y. Fermon].

A B

Figure 170. Nest of A: Oreochromis niloticus; B: Oreochromis macrochir.


A B C

D E F

G H I
Figure 171. Courtship and spawning in a mouthbrooder Cichlidae, Haplochromis burtoni from
Lake Tanganyika. The male is gray. A and B: The female lays eggs while the male remains
close to; C: After laying a few eggs, the female quickly turns; D: The female is preparing to
collect the eggs before the male has had time to fertilizers; E: Collection of eggs per female,
F: The male spreads his anal fin to the female and it shows the ocelli; G and H: The female
egg in the mouth, trying to collect these ocelli and closer to the orifice of the male genital
ejaculates at the time; I: The female begins to lay a new string of eggs. The entire sequence
is repeated several times.

The hatching takes place in the mouth of female 4 to 5 days after fecundation, and the vitelline
vesicle is completely resolved at the age from 11 to 12 days (Figure 174, p. 222). The duration of this
phase depends mainly on the temperature. As soon as the vitelline vesicle is resolved and that the
alevins are able to take exogenic food, the female lets escape from the mouth a cloud of juveniles
which is directed compared to the mother and takes refuge in its mouth with the least danger and
the call of its movements (Figure 172, p. 220).

A B

Figure 172. Mouthbrooding. A: The juveniles come in the mouth of their mother when any
danger. B: The juveniles in the mouth of their mother.


Females visit the nests
to lay their eggs

In breeding season,
males build their nest

Mouthbrooding
incubation by females

Non breeding adults live in
open water First fry live in group near the mother

Then, they live alone in group Light background

Separation of fish and down deeper and deeper as they grow
and habitat
selection

They seek later
sandy and muddy
areas

mud sand

Figure 173. Example of the life cycle of a maternal mouthbrooding tilapia.

When the alevins reach a size of 9 - 10 mm, they are freed definitively from their mother. This
one releases them out of not very deep water, on the edges, where they are organized in group and
continue their growth. The whole of the cycle is summarized in Figure 173, p. 221.
A female in good condition can reproduce at intervals from 30 to 40 days when the temperature
is of 25 with 28°C. The same female can produce 7 to 8 spawn per year, but all the females of a batch
are far from also frequently reproducing.


3 days 4 days after fertilization
Substrat spawners Mouthbrooders

Embryo
1 mm 1 mm
5 days

7 days

Juveniles Larvae
8 days

10 days

Figure 174. Different stages in Figure 175. Comparison between fry of substrate
mouthbrooders. spawners and mouthbrooders.

The number of eggs and alevins which a female can contain in its mouth varies according to its
size and the species. The record is undoubtedly held by Oreochromis mossambicus which reached
the size of 35 cm with 4 000 eggs.
For Sarotherodon melanotheron, the eggs of ocher yellow color and slightly pear shaped, reach
3 mm in diameter. They are incubated by the male. The alevins at hatching are 5 mm long and 9 mm
when the vitelline vesicle are resorbed.
II.3.3.THE GROWTH
The mode of reproduction and parental care has an influence on the size of the embryos and
their development. In general, from the physical constraint, the mouthbrooders can accommodate
only one limited number of eggs in the oral cavity (Figure 175 above).
According to the species, one can note that the maximum size and the size at sexual maturation
vary: the fish of the great lakes mature with a larger length and grow until a size more important than
those of the lagoons, ponds or rivers (Table XLIII, p. 223, Figure 176 and Figure 177, p. 224). In lake, the
size of maturation and the maximum length of the males and females do not differ. On the other
hand, in the small over-populated fields or stretches of water, the males grow more quickly than
the females whose size of maturation is lower than that of the males. This sexual dimorphism of
growth can be connected to the mode of parental care. As soon as the individuals reach the age of
maturity (1 to 3 years according to the sex and the field), the male individuals present a growth de-
finitely faster than the females and reach a definitely higher size. That can be understood insofar as
the males must establish a territory of reproduction and defend it. For the substrate spawners, this
difference is, as that gets along, less important. For the mouthbrooders, the male is generally more
dominating that its length is large. Each time one introduces a new male into the field, the males keep
a hierarchical basis and preserved this hierarchy until the arrival of the new intruder. What makes
the dominant? It takes the territory best placed and supervises it highly, attacking any male passing
in the vicinity and courting the females. It will thus invest energy in the defense of its territory at the
expense of its growth compared to the other males. However, the growth of the males will remain
higher than that of the females.
The fish in poor environmental condition mature with a size smaller than those which are in good
condition. If one finds individuals in a state of reproduction all the year, there exist nevertheless
peaks of reproduction which coincide with the two rainy seasons in equatorial region or at the single
rainy season under other latitudes. Moreover, the growth of Oreochromis niloticus is extremely va-
riable from one field to another, which suggests that the maximum size is more dependant on the
environmental conditions than of possible genetic differences. For example in the lake Chad in


Table XLIII. Size at sexual maturation, maximale size and longevity
of different species of tilapia.

Size at
Typical Maximale Longevity
Species Location maturation
/ Dwarf size (mm) (years)
(mm)
Alcolapia grahami Lake Magadi D 25 100
Oreochromis aureus Lake Kinneret T 190 315 5
Oreochromis esculentus Lake Victoria T 230 375 10
Lake Victoria, Kavirondo
T 230 330 7
Gulf
Lake Victoria, Jinja T 225 340 7
Lake Victoria, Mwanza T 240 325 7
Aquarium D 105
Pond D 164
Oreochromis leucostictus Lake Naivasha T 180 250
Lake Edward T 210 240
Lake George T 140 280
Lake Albert T 260 280
Lagon, Lake Albert D 100
Pond in Ouganda D 120
Pond in Kenya D 70
Oreochromis lidole Lake Malawi T 285 390 5
Oreochromis mortimeri Lake Kariba T 300 390 8
Lower Malolo T 180
Upper Malolo D 90
Oreochromis mossambicus Egypte T 300 7
Lake Sibaya D 100
South Africa T 390 11
Aquarium D 45
Oreochromis niloticus Egypt T 200 330 9
Lake George T 400
Lake Rudolf T 390 640
Crater, Lake Rudolf D 250
Lake Edward T 170
Lake Baringo T 260 360
Lake Albert T 280 500
Lagon, Lake Albert D 100
Oreochromis rukwaensis Lake Rukwa D 280
Oreochromis saka Lake Malawi T 275 340 5
Oreochromis shiranus shiranus Lake Malawi T 220 290 5
Oreochromis shiranus chilwae Lake Chilwa T 200 290 5
Oreochromis squamipinnis Lake Malawi T 240 330 5
Oreochromis variabilis Lake Victoria T 220 300 7
Sarotherodon galileus Lake Kinneret T 220 345 7
River Sokoto D 110
Tilapia mariae Nigeria, river Osse T 165 300
River Jamieson D 100
Lake Kariba T 450 5
Tilapia zillii Lake Kinneret T 135 270 7
Pond in Egypt T 130 250
Lake Naivasha D 90
Aquarium D 70


180

Mean weight (g) for fish less than 20 cm length
G
R
170

160
D A
E
150
C
140
K
130
T
120

110 B

100
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42
Maturation size (cm)
Figure 176. Relationship the weight of fish of 20 cm and the size of maturation
for Oreochromis niloticus for several geographic location. R: Lake Turkana;
A: Lake Albert; G: Lake George; E: Lake Edward; D: Lake Katinda; C: Lake Chanagwora;
K: Lake Kijanebalola; T: Lagoon Tonya of lake Albert; B: Lagoon Buhuku of lake Albert.

10
Pond Kijansi
5 ● ●

0 x x

15 Maturation size
Lagoon Buhuku
10
5
0
20
Lake Kijanebalola
15
10
5
Fréquency

0
35
Lake George
30
25
20
15
10
5
0
20
Lake Turkana
15
10
5
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66
Total length (cm)

Figure 177. Size class of Oreochromis niloticus
according several geographic location.


Lake Kinneret Mariout (Egypt) Chad
40 On
Tg On
30 Tg
Oau Tg
Tz Tz
20
Tz Oau
10

0
Oa Oa
Barotse Kafue (1) Kafue (2) m
40 Tr f Oa
Total length (cm)

Oma Tr
30
m
Oma f Oma
20

10

0

40 Lake Malawi Lake Victoria
Plover Cove
Ol Os
30 m
Osa f
Osh Ov m Omo
20 f
10 Lac Sibaya

0
0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10
Age (years)
Figure 178. Comparison of growth rate for different species in natural field by locality.
Oa: Oreochromis andersonii; Oau: O. aureus; Oe: O. esculentus; Ol: O. lidole;
Oma: O. macrochir; Omo: O. mossambicus; On: O. niloticus; Osa: O. saka; Osh: O. shiranus;
Ov: O. variabilis; Sg: Sarotherodon galileus; Tr: Tilapia rendalli; Tz: T. zillii.
40 1: Incomati, Limpopo 1: Lake Itasy
1
2: Dam of Doordraai 2: Kafue
35 2
3: Dam of Dam 3: Lake Aloatra
30 4: Lake Sibaya 3
1
25 4
2 5 1
3 2
20 6
3
4 1: Lake Albert
Standard length (cm)

15
2: Lake Itasy
10 3: Lake Chad
4: Lake Montasoa
5 5: Lake Mariout
A B 6: Lake Aloatra C
0
35
1: Lake Victoria 1: Lake Chad 1978
30 2: Lake Chad 2: Lake Chad 1980
3: Lake Mariout 1
3: Niger 2
2
25 1 4: Lake Mariout 1 2 3
4 3
20 3 5 4
6
1: Kafue
15
2: Lake Montasoa
10 3: Lake Itasy
4: Lake Liambezi
5 5: Lake Kariba
D 6: Lake Alaotra E F
0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
Age (years)
Figure 179. Comparison of growth rate for different species in natural field by species.
A: Oreochromis mossambicus; B: O. niloticus; C: O. macrochir;
D: Tilapia rendalli; E: T. zillii; F: Sarotherodon galileus.


Uganda, O. niloticus reaches 30 cm at the end of 3 years whereas in the lake Mariout in Egypt, 5
years are necessary to arrive at the same size. It is noted that, in the same field, the growth of O. ni-
loticus is generally higher than that of other species of tilapia for long time (Figure 178 and Figure
179, p. 225). It reaches 300 to 500 g in 8 months, O. leucostictus 300 g, Tilapia zillii 250 to 400 g. It
is of a maximum of 3 g/day under optimal conditions.
There exist other piscivorous species of Cichlidae, which are used in polyculture for the control
of the populations of tilapia.
Ö The group of “green” Hemichromis. It is about a complex of species with two major species:
H. elongatus and H. fasciatus. The other species of the genus belongs to the group of Hemichromis
“red” were also tested but without success because of their rather omnivorous then piscivorous.
Ö The fish of the genus Serranochromis, which are the large predatory ones of Southern and East
Africa.

Ö The tilapia are:
Ö Robust fish,
Ö Highly plastic and adapt to environnemental conditions,
Ö With elaborated parental care,
Ö They are opportunistic in terms of diet.

III. THE BIOLOGY OF SILURIFORMES OR CATFISH
More known under the name of catfishes, Siluriformes (Siluroidei more precisely) are an impor-
tant group for fishfarming. Their worldwide production (more than 300 000 tons/year) is currently at
the fourth rank of the species cultivated out of fresh water after carps and other Cyprinidae, Salmo-
nidae and the tilapia. With their great diversity of forms and biological characteristics, Siluriformes,
represented by more than 2500 described species, can contribute to the valorization of the aquatic
resources through diversified systems of production. Today, if the farming of some species of Siluri-
formes already emerged on a level economically significant of fishfarming production, the potential
offered by the biological diversity of this group for the aquaculture remains still largely ignored and
needs a constant research effort. In Africa, only few species were used, mainly of the family of Cla-
riidae. However, knowledge of the biology of these species remains still scattered for the majority.
But, several can be used as species of supplements and/or control of the populations while bringing
some more weight produced in the ponds.

III.1. THE CLARIIDAE
Few studies was undertaken on biology Clariidae African used in fishfarming. The data thus
remain scattered.
III.1.1.THE TAxONOMY
The Clariidae are distinguished from other Siluriformes by the absence of a dorsal-fin spine, the
very long dorsal and anal fins, the eel-shaped body, and the presence of four pairs of barbels as
well as of a suprabranchial organ, formed by outgrowths of the second and fourth gill arches, which
enable these fishes to practice aerial respiration.
Several species, in particular those of the genera Clarias and Heterobranchus, play an important
role in fishery and fishfarm. Two species are presented in Appendix 05 p. 272.
The genus Clarias is characterized by the presence of a single, long dorsal fin that extends to
caudal-fin base. The adipose fin is absent (except in one species with a reduced adipose fin). Vertical
fins are not confluent. Body is more or less elongate. Head is flattened. Lateral cephalic bones are


contiguous. Eyes are small, with a free margin. More than 35 described species of Clarias are found
in Africa.
The genus Heterobranchus is characterized by the presence, between the rayed dorsal and the
caudal fin, of a large adipose fin supported by prolonged neural spines. Head is flattened. Lateral
cephalic bones are contiguous. Eyes are small, with a free margin. Only, 5 species are known.
III.1.2. THE FEEDING HABIT
Few studies have focused on the nutritional needs of Clariidae, in particular for Clarias gariepinus
and to a lesser extent still of Heterobranchus longifilis in natural environment. The rare studies car-
ried out show a similarity in the cover of the general needs for the two species.
Clarias gariepinus feeds on the bottom and are omnivorous. He eats insects, crabs, plankton,
snails and fish but also of young birds, dead bodies, plants and fruits, the diet is variable according
to the size.
Other Clariidae are all, generally, according to knowledge on their food, omnivores. Several spe-
cies have, however, a tendency to feed on fish mainly.
For Heterobranchus longifilis, the first food catch of alevins is carried out as of the 2 days age,
whereas the vitelline vesicle is not yet entirely resorbed. At this stage, the alevins, whose width of
the mouth is from approximately 1 mm, are already able to eat planktonique preys of big size. The
diet, primarily zooplanktonophagous until the age of 5-6 days, tends thereafter to diversify gradually
with the incorporation of insects of increasing size, mainly of larvae of chironomids. At this stage,
one also finds, in the stomach contents, shells of gastropods, organic detritus, remains of plants,
and seeds, who represent the evolution of the diet into that of the adult, considered like an omnivore
with carnivorous tendency. The alevins are feed continuously day and night, without an unspecified
rhythm in the food catch not being highlighted.
Clariidae are primarily night fish.

80 30

70 E
Hatching and relative fecundity (%)

T°
Rainfall (cm) and Temperature (°C)
60

20
50

40

30
P
10

20

10 FR

0
J F M A M J J A S O N D
Mois
Figure 180. Relative Fecundity (% of total weight), % of hatching (% total eggs) of Clarias
gariepinus, monthly average rainfall and average temperature. Brazzaville.


III.1.3. THE REPRODUCTION
The size of the first maturation ranges between 40 and 45 cm for the females and between 35
and 40 cm for the males for Clarias gariepinus. The eggs are greenish. Incubation is approximately
33 hours at 25°C.
Oviparous animals, the reproduction ocurs during the rainy season (Figure 180 below). The fish
make lateral migrations in the flooded plains to reproduce then return in the lakes or major beds of
the rivers.
In the majority of the African countries, the cycle of reproduction of the catfish begins at the
beginning of the rainy season. The final stimulus of the spawning time seems to be associated with
the rise of water and the flood of the marginal zones. During the spawning time, large groups of male
and female catfishes adult concentrate at the same place, in water at depth often lower than 10 cm,
in edge of lakes or calm water. The African catfish spawns in captivity on a large variety of substrates,
including fibers of sisal, sheets of palm tree and stones.

B
A

C
E

D
Figure 181. Courtship in Clarias gariepinus. A: The male (in gray) approach the female;
B and C: The male surrounded the head of the female and keep it firmly;
D: The sperm and egg cells are released into the environment and the females scatters them
by movements of tail; E: The couple rests.


36 h
1 mm
Incubation
1 mm

1 mm
48 h
Hatching
1 mm

6 j
1 mm
12 h
1 mm

9 - 12 j
1 mm

1 mm 24 h

Figure 182. First stages of development for Clarias gariepinus.
v ed v ed

J3 rc J4 rc J4
J3
rd ea
J6 ea
J5 aa
J5 rd
bp J6
ra
bpe
J7 bp
J8
J7
bpe

J8
ra
5 mm

J10
J10
5 mm

J14 J14

J17 J17

A B
Figure 183. Several stages of larval development until 17 days.
A: Clarias gariepinus; B: Heterobranchus longifilis.
aa: adipose fin start; bp: burgeon of the pectoral; bpe: burgeon of the pelvic;
ea: start of the anal rays; ed: start of the dorsal rays;
ra: anal rays; rc: caudal rays; rd: dorsal rays; v: vesicles.


During the parade, which can last several hours, the female of the catfish deposits its eggs by
small groups. The courtship is preceded by fighting of males. The couples are isolated. The male
puts itself in U around the head of the female. The eggs and sperm are released; then, followed by
movements of its tail, the female scatters eggs on an important surface. The couple rests several
minutes after the spawning (Figure 181, p. 228). The partner fertilizes at the same time each group of
eggs by releasing a cloud of milt above eggs. The eggs adhere finally to the submerged vegetation.
In captivity, much of eggs are destroyed by the violence of the blows of tail. After the spawning time,
the group of catfishes turns over out of deeper water. There is no parental protection for eggs. After
a few weeks, the catfish produces a group of eggs again and prepares with a new spawning time.
One second spawning time will be caused by the rains or a new flood. Several spawning times
can follow one another thus the same year. The eggs hatch after 24 to 36 hours, according to the
temperature of water. The larvae, destined for this stage vesicled larvae, hide in the vegetation. The
fry and fingerlings of African catfish are difficult to find in nature. It is probably due to the strong
mortality of eggs and the larvae.
There is no parental care except the choice of the site of spawning. The development of eggs
and the larvae is fast and the fingerlings are free 48 to 72 hours after fecundation (Figure 182 and
Figure 183, p. 229). The fingerlings remain in the flooded zones and will migrate when they reach 1.5
to 2.5 cm length.
For Heterobranchus longifilis, the eggs are with a broad adhesive disc. Their incubation is car-
ried out in stagnant water and with the darkness. To 27 - 29°C, the hatching occurs 24 to 28h after
fecundation.
III.1.4. THE GROWTH
Growth rates appeared very promising. Thus all the studies on large Clarias and Heterobranchus
give almost linear growth beyond the age of one year (Figure 184 below).
For Heterobranchus longifilis, the fish reached on average 900 g in 6 months starting from
an average weight of 25 g, during tests in freshwater ponds. Between 100 and 500 g, the rate
of growth exceed 5 g/day.
For Clarias gariepinus, the fish reached 500 to 1000 g in 8 months.

140 800
Ln
130 Hl
700
120
Standard or total length (cm)

110 Cg
600
100
Hl
Body weitgh (g)

90 500
80
70 400 Cg
Cs Cg
60
300
50
40
200
30
20 100
10 50
0 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 10 28 56 84 112 140 168 196 224 254
Age (years) Days

Figure 184. Compared growth of several African fish species.
A: According the size; B: According the weight.
Cs: Clarias senegalensis; Cg: Clarias gariepinus; Hl: Heterobranchus longifilis;
Ln: Lates niloticus.


III.2. THE CLAROTEIDAE AND AUCHENOGLANIDIDAE
These catfishes are characterized by the presence of two to four pairs of barbels, well developed
pectoral-fin spines, a moderately or strongly developed adipose fin, and a medium-sized anal fin.
Mouth is supported dorsally by the premaxilla and part of the maxilla
Other catfish used in fish farming, we may note the fish of the genus Chrysichthys and the spe-
cies Auchenoglanis occidentalis (Photo X, p. 232). Before under the same family, these genera have
been put in two distincts families.

III.2.1. THE GENUS CHRYSICHTHYS
From the family of Claroteidae, the genus Chrysichthys is characterized by the presence of four
barbels; 6 (rarely 5 or 7) branched dorsal-fin rays preceded by a very short first spine and a well
developed second spine, weakly denticulate along posterior margin; a small or medium-sized, never
ossified, adipose fin (its base shorter than head width); pectoral fins with 8-11 branched rays pre-
ceded by a strong spine which is distinctly denticulate along posterior margin; pelvic fins inserted at
about mid-length of body, with 1 spine and 5 soft rays; a medium-sized anal fin with 3 to 6 spines
and 6-12 branched rays; and a deeply forked caudal fin. Eyes are large, positioned laterally, their
margin free. Body is moderately elongate, 4-6 times longer than deep.
Chrysichthys, more known under the local name of “mâchoiron”, is a fish very appreciated in
Côte d’Ivoire and West Africa in general. The many traditional receipts based on “mâchoiron” in the
local restaurants (maquis) illustrate the attachment to the festive character of these species. It is easy
besides to observe that the largest sales take place the day before the great festivals. The name of
“mâchoiron” includes three species of the genus Chrysichthys: C. maurus, C. nigrodigitatus and
C. auratus. The distinction between Chrysichthys maurus and C. auratus is not always easy because,
for individuals of comparable size, the interspecific morphological differences are tiny whereas in-
traspecific variability can be very large in particular according to the seasons. On the other hand, the
distinction of these two species with C. nigrodigitatus is easy because of its larger size and its rather
silver gray coloring, whereas its yellowish for C. maurus and C. auratus.
The “mâchoirons”, benthic fish, feed mainly, at the adult stage, of organic detritus and inver-
tebrates: larvae of insects (chironomids, dipters), planktonic crustaceans, molluscs. On the other
hand the fingerlings, until the size of 15 cm, seem to feed on zooplankton primarily. Chrysichthys are
robust species resisting well to handling and able to temporarily support weak partial oxygen levels.

■ CHRYSICHTHYS MAURUS
In wild, C. maurus has a relatively slow growth, it reaches approximately 12 cm (more or less
25 g) in one year. When it is rise in pond with a density of 3 fish per m2 and feed with an artificial food
to 33% of proteins, C. maurus passes from 11 g to 200 g in 12 months.
C. maurus can reproduce from 10 months age. The size of small mature individuals is from 9 to
11 cm in the rivers of Côte d’Ivoire.
In wild, the reproduction of C. maurus is seasonal. Ovocytes of small diameter (100 - 150 µm)
can be observed at the beginning of the great rainy season (either in April - May). The arrival of conti-
nental freshwater and the fall of the temperature of water (passing then to 26 - 29°C) seem to have
an influence on the beginning of the process of reproduction of this species. The activity of spawning
begins in June and is spread until November - December. During the dry season, as from January,
the couples still in reproduction are rare. For the mating and the deposit of eggs, this species seeks
crevices (rocks, deadwood, bamboos…). The parents generally remain in the nest with alevins until
the resorbtion of their vitelline vesicle. The sexual dimorphism is very marked: the mature male is
recognized by a broader head and the female by a plumpness of the abdomen and a bulge of the
urogenital papilla. Relative fecundity is about 15 to 20 ovocytes per g of weight of female. The same
female produces only one clutch each year.


■ CHRYSICHTHYS AURATUS
The biology of C. auratus seems very close to that of C. maurus but with a definitely lower
growth. This species is not of thus any fishfarming interest.
■ CHRYSICHTHYS NIGRODIGITATUS
In wild, C. nigrodigitatus reaches 18 cm (fork length) in one year, 24 cm in two years and 30 cm
in three years. Studies showed that raised out of basin, it spent eleven months to pass from 15 g
(11 cm) to 250 g (26 cm). In a wild state, C. nigrodigitatus in general reproduces from the size of 33
cm (3 years old) with a behavior similar to that of C. maurus (search for receptacle of spawn by the
pair). The relative fecundity of this species is close to that of C. maurus. It is given, on mean, a value
of 15 ovocytes per g of weight of female, with extreme values of 6 and 24.
The hatching intervenes 4 to 5 days after at the temperature of 29 - 30°C by giving larvae from
25 to 30 mg equipped with an important vitelline bag which reabsorbs gradually in ten days. They
reach 350 - 400 g into 8 to 10 months.
There exists in the adult females a progressive and synchronous development of the gonads cor-
responding to the reproductive season well marked. The spawning begin at the end of August and
their frequency is maximum between September and October (more than 50%). One observes then
a fall around at the end of November and the activity of spawning is completed in December. Howe-
ver, it should be noted that if the majority of the spawnings is located regularly between September
and November, the annual maximum moves appreciably according to the years.

A

B

C
Photo X. Claroteidae. A: Chrysichthys nigrodigitatus [© Planet Catfish];
B: C. maurus [© Teigler - Fishbase];
Auchenoglanididae. C: Auchenoglanis occidentalis [© Planet Catfish].


III.2.2. THE GENUS AUCHENOGLANIS
From the family of the Auchenoglanididae, the genus Auchenoglanis is characterized by its
slightly elongate body, three pairs of barbels (one maxillary and two mandibular) and the position of
the anterior nostril on upper lip. Dorsal fin with 7 branched rays preceded by 2 spines, the first small,
the second strong and denticulate; adipose fin originating shortly behind the dorsal; pectoral fins
with 9 branched rays preceded by a strong spine; pelvic fins well developed, with 6 rays, 5 of them
branched; anal fin medium-sized, with 6-8 branched rays; caudal fin emarginate.
This species has been tested in Côte d’Ivoire at Bouaké. Growth rates have been quite low and
the test was not renewed.

III.3. THE SCHILBEIDAE
The Schilbeidae (a catfish family found in Africa and Asia) are characterized by a dorso-ventrally
flattened head, a rather short abdomen, a laterally compressed caudal region, and an elongate anal
fin (Photo Y below). Dorsal fin is short, sometimes absent. Pectoral fins are provided with a spine (as
also the dorsal fin of most species). Three or four (depending on species) pairs of barbels are found
around mouth. The Schilbeidae are moderately good swimmers with laterally compressed bodies,
as opposed to the majority of bottom-living siluriform fishes which are anguilliform or dorso-ventrally
flattened. Five genera have so far been recognized in Africa: Parailia, Siluranodon, Irvineia, Schilbe
and Pareutropius. The three first genera have only a low economic value because of their small size.
However, some species of the genera Irvineia and Schilbe may reach large size (50 cm or more) are
very appreciated.
For Schilbe mandibularis, the size of the first sexual maturity presents a variation along the river
(upstream, lake and downstream) for the two sexes. It is slightly weaker in the males than in the
females (12.3 cm compared with 14.8 upstream and 14.8 against 18.1 cm downstream). The relative
data with the evolution of sexual maturity and the gonado-somatic ratio reveal a seasonal cycle of
reproduction distinct. The species reproduces in rainy season from April to June then from August
to October. The maximum activity of reproduction occurs from April to June, corresponding to the
peak of pluviometry. The sexual rest occurs during the dry season, from December to March. Ave-
rage relative fecundity reaches 163600 ovocytes per kg of body weight, with a minimum of 15308
ovocytes and a maximum of 584593. The diameter of the ovocyte at the spawn is approximately of
1 mm. A negative effect of the lake environment on certain biological indicators of the reproduction
(size of the first sexual maturity, sex-ratio, average body weight and fecundity) was highlighted. This
influence of the lake could be due to the strong pressure of fishing which is exerted there.
The fish of the genus Schilbe become piscivorous towards 13 - 14 cm TL. They are fish usable
for the control of the populations of tilapia.

III.4. THE MOCHOKIDAE
All representatives of this family have a scaleless body and three pairs of barbels, one maxillary
and two mandibular pairs, except in some rheophilic forms in which the lips are modified into a suc-
king disk. Nasal barbels are absent. First dorsal fin have an anterior spinous ray, adipose fin is large
and sometimes rayed. First pectoral-fin ray is spinous and denticulate. A strong buckler present on
head-nape region. Eleven genera and nearby 180 species are known (Photo Z, p. 234).
Several species of the genus Synodontis can reach a large size (more than 72 cm) and represent
a clear commercial interest. Some could be used as species of complements for polyculture.

Photo Y. Schilbeidae. Schilbe intermedius [© Luc De Vos].


A

B

Photo Z. Mochokidae. A: Synodontis batensoda [© Mody - Fishbase]
B: Synodontis schall [© Payne - Fishbase].

IV. THE OTHER FAMILIES
Other fish have been tested and needs tests in fishfarming.

IV.1. THE CYPRINIDAE
It is the family of the Carps which are usually used in fishfarming.
The fish of the family Cyprinidae have a body covered with cycloid scales and a head naked. All
rayed fins are well developed, but adipose fin is absent. Mouth is protrusible, lacking teeth. Some-
times one or two pairs of more or less well developed barbels are present. Lower pharyngeal bones
very well developed, are bearing a few teeth aligned in 1-3 rows.
In spite of fish of large size observed in Africa, such as for example of the genera Labeo, Va-
ricorhinus and Barbus, few of them were used in fishfarming. It is the case of Labeo victorianus in
East Africa and Labeo coubie in Côte d’Ivoire. The major part of the large species are, however, from
running water (Photo AA, p. 235).

IV.2. THE CITHARINIDAE
The Citharinidae comprise large, deep-bodied and compressed fishes. Following genera, scales
are cycloids (Citharinops and Citharinus) or ctenoids (Citharidium). The lips have tiny monocuspid
teeth and the mouth is terminal. On the other hand, the very tiny maxillary is toothless. All species
have two dorsal fins. The first has 16 to 24 branched rays. The second adipose is quite large. Dorsal
fin has 19-24 branched rays. Lateral line is straight, median and complete (47-92 scales). Finally, as
a common characteristic of African Characoids, pelvic fins are provided with a scaly process. All
species are very high specialised microphagous. They have numerous thin and dense gill rakers. The
most remarkable particularity is the presence of a complex suprabranchial organ, which acts like a
suction-force pump to concentrate and spin foods before swallowing them. The Citharinidae are not
very abundant but they are of great economic importance. All species show a large size. In Chad
basin the maximum reported size for Citharinops distichodoides is 840 mm SL and 18 kg weight. The
farming of Citharinus citharus was tested but without continuation. It is a herbivore. (Photo AB, p. 235).


A

B

Photo AA. Cyprinidae. A: Barbus altianalis; B: Labeo victorianus
[© Luc De Vos, © FAO (drawings)].

A

B

Photo AB. Citharinidae. A: Citharinus gibbosus; B: C. citharus [© Luc De Vos].


A

B

Photo AC. Distichodontidae. A: Distichodus rostratus; B: D. sexfasciatus [© Fishbase].

IV.3. THE DISTICHODONTIDAE
The Distichodontidae belong to the order of the Characiformes. This family, which is endemic to
Africa, can be identified by the following characters: body elongate (deeper in Distichodus), scales
ctenoid, adipose fin generally present, lateral line in mid-lateral position, and teeth well developed.
The fish of the genus Distichodus can reach large size (80 cm SL). D. rostratus (76 cm TL, weight
of 6 kg) have been tested for fishfarming (Photo AC above). They are mainly herbivorous species.

IV.4. THE CHANNIDAE
The Channidae (formerly Ophicephalidae) are a freshwater fish family occurring in Africa and
Asia. The body is elongate and cylindrical in cross-section, covered with cycloid scales. Unpaired
fins are long, comprising soft rays but no spines. An accessory breathing organ present in the form
of two suprabranchial pharyngeal cavities that permit direct breathing of atmospheric air, allowing
the fish to survive for long periods outside the water.
A single genus, Parachanna, occurs in Africa; it comprises three species, two of which are found
in the area considered here. Parachanna obscura may reach 34 cm SL and he is a piscivorous which
is perfectly appropriate for the control of the populations of tilapia in the ponds (Photo AD, p. 236).

Photo AD. Channidae. Parachanna obscura (DRC) [© Y. Fermon].


IV.5. THE LATIDAE
The Latidae is characterized by the possession of a scaly process at bases of pelvic fins. The
shape of the second suborbital bone which is not fused to the preopercle and bears a subocular
blade extended backwards into a point. A strong notch is separating the two dorsal fins.
In this family, it is the famous Nile Perch called also «Capitaine» in West Africa, Lates niloticus,
which was the subject of test in fishpond (Photo AE below). It is this species which have been intro-
duced in lake Victoria in the Sixties. Problems appears, because the cannibalism and the tolerance
to the oxygen level.
This species can reach 200 cm for a weight of 200 kg. Its growth is quite linear (Figure 184, p. 230
and Figure 185, p. 238).
Piscivorous, this species can be used for the control of tilapia in ponds.

IV.6. THE ARAPAIMIDAE
The Arapaimidae, a very ancient family, is characterized by its ovaries lacking oviducts. Today it
is represented by only four monospecific genera: one from Australia, Sumatra and Borneo (Sclero-
pages), two from the Guyana and Brazil with the famous Arapaima gigas which can reach 200 cm for
a weight of 200 kg, and one, Heterotis, from Africa.
Body is laterally compressed and covered with large bony scales of a somewhat horny consis-
tence. Lateral line is complete. Fins is spineless. Maxillary and premaxillary teeth are present but
pharyngeal teeth are absent.
Only one species occurs in Africa, Heterotis niloticus. A presentation file can be consulted in
Appendix 05, p. 274.
Its main characteristics are:
9 A rapid growth: 3 g /fish/day or more. Large size, higher than 100 cm length (Figure 185, p. 238).
9 A delicate reproduction. It requires a low depth and herbaceous vegetation. He likes space.
The nests of Heterotis niloticus are built in the herbaceous vegetation. They are comparable

Photo AE. Latidae. Lates niloticus [© Luc De Vos].


90 100 1
1
90 2
80 2 3
80 6
5
70
3
7
70
8 - 9
60

10

60
50
50

40
40 4   1: Delta of Nil
  2: Niger
30   3: Chari
30   4: Nil at Khartoum
  5: Lake Chad, south
20   6: Lake Chad, north
20
1: Nyong   7: Lake Kyoga
2: Niger   8: Lake Turkana
10 10
3: Upper Niger   9: Lake Albert
10: Lake Nasser
0 0
0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9
A Age (years) B Age (years)

Figure 185. Growth of Heterotis niloticus (A) and of Lates niloticus (B).

with small basins measuring approximately 1.2 m in diameter, the center slightly excavated located
at approximately 30 cm of depth. The bottom is naked and is generally well flattened. The compact
edges are 20 cm thickness at the top and are slightly above water. It are built with the stems of the
plants which were removed from the center of the nest. The parents remain near the nest when the
eggs are laid.
The eggs are rather small (2.5 mms diameter) and orange. They hatch approximately two days
after the spawning. The larvae have long branchial filaments, red dark, which are prolonged outside
the opercle. They quickly form a swarm of approximately 30 cm in diameter occupying the center of
the nest. The 5th or the 6th day, the alevins leave the nest, always in dense swarm, and under the
protection of the parents.
The juveniles of Heterotis niloticus live in swarm, then in groups whose the number decrease
progressively with the growth.
9 It is a microphage - planktivorous but with omnivorous tendency.

Ö The African species are numerous and many may be used in fish farming. However,
in the context of livelihoods, will be chosen:
Ö A tilapia for the main production; with
Ö A piscivorous species.
Ö We may also use other species in the pond as an omnivorous species and / or her-
bivore species.
Ö The choice of species will depend on the geographic location of ponds (ichthyore-
gions).


Appendix 04
BIOGEOGRAPHIC DATA

To complete the chapter 03 p. 21, the reader will found here informations on:

Table XLIV. Some characteristics of African countries;

Table XLV. Characteristics of ichthyoregions and lakes in Africa;

Figure 186. Repeat of the map of ichthyoregions and countries;

Table XLVI. The ichthyoregions and their repartition by country in Africa;

Table XLVII. The genera and species of tilapias recorded by countries in Africa.

The user on the field, therefore, by cross, know in each ichtyoregion he is and which species of
tilapia is present in its area of intervention.


TABLE xLIV. Some characteristics of African countries.
Region: Region in which is the country
Population in inhabitants - Surface in km2 - Density in inhabitant / km2
H = Possible Habitats for fisheries in km2
HS = % of possible habitats / surface of the country
PM = Mean production between 2000 and 2004 in tonnes
Prod = Productivity
Icht = Number of ichtyoregions whose a part is included in the country
Family, Genera, Species: Number of famiy, genera and species of fish known from the
country

Country Region Population Surface Density H HS
South Africa Austral 44187637 1219090 36.2 13386 1.1

Algeria North 33333216 2381741 14.0

Angola Austral 13115606 1246700 10.5 22976 1.8

Benin Sub-Sahara 7862944 112622 69.8 2958 2.6

Botswana Austral 1639833 581730 2.8 36390 6.3

Burkina Faso Sub-Sahara 13902972 274200 50.7 1901 0.7

Burundi Sub-Sahara 8691005 27834 312.2 2559 9.2

Cameroon Sub-Sahara 17340702 475442 36.5 19638 4.1

Cape Verde Sub-Sahara 455294 4033 112.9

Central Africa Sub-Sahara 4303356 622984 6.9 11771 1.9

Comoros Oriental 690948 1862 371.1

Congo Sub-Sahara 3702314 341999 10.8 59212 17.3

Congo (DR) / Zaïre Sub-Sahara 62660551 2344798 26.7 113724 4.9

Côte d’Ivoire Sub-Sahara 17654843 322461 54.8 4928 1.5

Djibouti Oriental 768900 23200 33.1

Egypt North 78887007 995450 79.2 20989 2.1

Erythrea Oriental 4786994 121320 39.5

Ethiopia Oriental 74777981 1127127 66.3 22048 2.0

Gabon Sub-Sahara 1424906 267667 5.3 8524 3.2

Gambia Sub-Sahara 1641564 11295 145.3 2290 20.3

Ghana Sub-Sahara 22409572 238538 93.9 13871 5.8

Guinea Sub-Sahara 9690222 245857 39.4 5090 2.1

Equatorial Guinea Sub-Sahara 540109 28051 19.3 222 0.8

Guinea-Bissau Sub-Sahara 1442029 36125 39.9 3756 10.4

Kenya Oriental 34707817 581787 59.7 30576 5.3

Lesotho Austral 2022331 30355 66.6 6 0.0

Liberia Sub-Sahara 3631318 111370 32.6 342 0.3

Libya North 5900754 1759540 3.4


TABLE xLIV (next). Some characteristics of African countries.
Prod = Productivity
country

Country PM Prod Icht Families Genera Species
South Africa 900 0.7 3 47 113 224

Algeria 3 10 16 23

Angola 8800 3.8 3 42 112 294

Benin 28919 97.8 1 46 108 182

Botswana 141 0.0 2 13 37 96

Burkina Faso 8700 45.8 2 29 67 140

Burundi 13081 51.1 2 15 30 57

Cameroon 56500 28.8 3 55 163 498

Cape Verde 1 1 1

Central Afric 15000 12.7 2 31 98 320

Comoros 12 23 28

Congo 25765 4.4 2 50 160 409

Congo (DR) / Zaïre 212000 18.6 6 65 265 1104

Côte d’Ivoire 14366 29.2 2 49 113 241

Djibouti 1 5 5 5

Egypt 287387 136.9 4 46 146 230

Erythrea 2 8 9 10

Ethiopia 12518 5.7 3 3 3 3

Gabon 9493 11.1 1 43 106 249

Gambia 2500 10.9 1 36 57 86

Ghana 74700 53.9 2 56 137 262

Guinea 4000 7.9 3 35 91 266

Equatorial Guinea 1015 45.8 2 22 30 38

Guinea-Bissau 150 0.4 1 27 47 78

Kenya 147442 48.2 6 34 75 193

Lesotho 37 63.4 1 5 11 15

Liberia 4000 116.8 2 37 75 178

Libya 3 4 5 8


Prod = Productivity
country

Country Region Population Surface Density H HS
Madagascar Oriental 18595469 587041 31.7 10555 1.8

Malawi Austral 13013926 118484 109.8 27526 23.2

Mali Sub-Sahara 11956788 1240198 9.6 54034 4.4

Morocco North 33757175 458730 73.6 4777 1.0

Mauritius Oriental 1248592 2040 612.1

Mauritania Sub-Sahara 3177388 1030700 3.1 21284 2.1

Mayotte (France) Oriental 201234 375 536.6

Mozambique Austral 19686505 799380 24.6 46763 5.8

Namibia Austral 2044147 825112 2.5 16353 2.0

Niger Sub-Sahara 12525094 1186408 10.6 44249 3.7

Nigeria Sub-Sahara 131859731 923768 142.7 58480 6.3

Uganda Oriental 30262610 241548 125.3 50078 20.7

Reunion La (France) Oriental 787584 2504 314.5

Rwanda Sub-Sahara 8648248 26338 328.4 2416 9.2

Western Sahara North 300905 266000 1.1

Saint-Helena Austral 7502 410 18.3

Sao Tome & Principe Sub-Sahara 193413 1001 193.2

Senegal Sub-Sahara 11987121 196722 60.9 13965 7.1

Seychelles Oriental 83688 455 183.9

Sierra Leone Sub-Sahara 6005250 71740 83.7 4771 6.7

Somalia Oriental 8863338 637657 13.9 12903 2.0

Sudan Oriental 41236378 2505810 16.5 71237 2.8

Swaziland Austral 1136334 17365 65.4 33 0.2

Tanzania Oriental 37979417 945088 40.2 101015 10.7

Chad Sub-Sahara 10542141 1284200 8.2 152252 11.9

Togo Sub-Sahara 5681519 56785 100.1 1401 2.5

Tunisia North 10175014 163610 62.2 10366 6.3

Zambia Austral 11502010 752612 15.3 73065 9.7

Zimbabwe Austral 12382920 390757 31.7 3927 1.0


Prod = Productivity
Family, Genera, Species: Number of family, genera and species of fish known from the
country

Country PM Prod Icht Families Genera Species
Madagascar 30000 28.4 1 24 39 52

Malawi 48391 17.6 5 17 99 402

Mali 101974 18.9 3 31 76 172

Morocco 1577 3.3 2 14 17 23

Mauritius 20 41 59

Mauritania 5000 2.3 3 35 68 109

Mayotte (France) 7 12 13

Mozambique 11792 2.5 5 38 117 229

Namibia 1500 0.9 5 14 38 82

Niger 33587 7.6 2 24 52 91

Nigeria 166193 28.4 1 57 147 362

Uganda 255116 50.9 5 20 54 226

Reunion La (France) 19 34 50

Rwanda 7071 29.3 3 10 24 68

Western Sahara 1 6 7 7

Saint-Helena 0 0 0

Sao Tome & Principe 5 6 6

Senegal 50431 36.1 2 49 98 175

Seychelles 18 26 33

Sierra Leone 14000 29.3 1 34 81 185

Somalia 200 0.2 2 12 20 33

Sudan 52200 7.3 3 27 60 116

Swaziland 70 21.4 1 10 18 35

Tanzania 287443 28.5 6 30 129 449

Chad 75640 5.0 2 31 67 139

Togo 5000 35.7 1 40 79 150

Tunisia 894 0.9 2 10 14 18

Zambia 65334 8.9 4 23 117 352

Zimbabwe 13023 33.2 1 18 42 91


TABLE xLV. Characteristics of ichthyoregions and lakes in Africa.
N°: These letters are on the figure 186 next page
Drainage basins: Number drainage basins which are in the ichthyoregion
Families, Genera, species: Number of families, genera and species of fish known from
the ichthyoregion

Surface
N° Ichtyoregion Drainage basins Families Genera Species
area (km2)
A Angolese 520 000 131 34 78 184
B Lower Guinea 622 000 116 56 176 511
C Cap 232 000 158 27 49 78
D Congolese 3 453 000 3 66 228 983
E Upper Guinea 261 000 116 43 105 286
F Karroid 1 087 000 77 32 64 107
G Maghreb 1 588 000 438 22 40 60
H Madagascar 596 000 364 24 39 52
I Nilo-soudanian 9 668 000 74 70 218 653
Nilo-soudanian
J 425 000 108 57 148 320
(Eburneo-ghanean)
K Oriental 1 905 000 249 41 88 214
L Sherbro Island 1 900 24 7 7 9
M Zambezis 2 949 000 115 46 27 303
N Zanzibar Island 23 000 1 4 6 12
O Non defined 1 (Red sea) 61 000 48 15 34 46
P Non defined 2 (Abyssinia) 956 000 425 31 72 99
Q Non defined 3 (Namibia 1) 176 000 33 1 1 1
R Non defined 4 (Namibia 2) 71 000 23 0 0 0
S Non defined 5 (Sahara) 4 462 000 58 8 10 13
a Lake Amaramba 3 100 1 7 10 17
b Lake Chilwa / Lago Chiuta 9 800 1 10 23 39
c Lake Edward / Édouard 24 000 1 12 24 62
d Lake Georges 25 000 1 10 20 50
e Lake Kivu 7 300 1 7 12 38
f Lake Malombe 2 000 1 8 31 48
g Lake Naivasha 3 500 1 3 3 3
h Lake Natron 22 000 1 2 3 9
i Lake Nyasa / Malawi 128 000 1 13 88 375
j Lake Ruhondo 1 700 2 4 5 8
k Lake Rukwa 75 000 1 14 27 60
l Lake Tanganyika 233 000 1 25 112 371
m Lake Victoria 309 000 2 16 45 205


G Mediterranean sea

O
S

Red sea

I
P

E
J
L N
c d
K
B j m g Indian ocean
e h
D
l
k
A i
a
f b
Atlantic ocean M
Q H

R
F

C

Figure 186. The ichthyoregions (limits in yellow-green) and the countries (limits in red)
(Faunafri).


TABLE xLVI. The ichthyoregions and their repartition by country in Africa.

Number ichthyoregion
Ichthyoregions

(Eburneo-ghanean)
Nilo-Soudanian

Zanzibar Island
Nilo-soudanian

Sherbro Island
Upper Guinea
Lower Guinea

Madagascar
Congolese

Zambesis
Angolese

Maghreb

Oriental
Karroid
Country

Cap
South Africa 3 1 1 1
Algeria 3 1 1
Angola 3 1 1 1
Benin 1 1
Botswana 2 1 1
Burkina Faso 2 1 1
Burundi 2
Cameroon 3 1 1 1
Central Africa 2 1 1
Congo 2 1 1
Congo DR / Zaïre 6 1 1 1
Côte d’Ivoire 2 1 1
Djibouti 1
Egypt 4 1
Erythrea 2 1
Ethiopia 3 1 1
Gabon 1 1
Gambia 1 1
Ghana 2 1 1
Guinea 3 1 1 1
Equatoriale Guinea 2 1 1
Guinea-Bissau 1 1
Kenya 6 1 1 1
Lesotho 1 1
Liberia 2 1 1
Libya 3 1 1
Madagascar 1 1
Malawi 5 1
Mali 3 1 1
Morocco 2 1
Mauritania 3 1 1
Mozambique 5 1 1
Namibia 5 1 1 1
Niger 2 1
Nigeria 1 1
Uganda 5 1
Rwanda 3
Western Sahara 1 1
Senegal 2 1 1
Sierra Leone 1 1
Somalia 2 1
Sudan 3 1
Swaziland 1 1
Tanzania 6 1
Chad 2 1
Togo 1 1
Tunisia 2 1
Zambia 4 1 1
Zimbabwe 1 1
Number of country 48 2 5 1 6 5 4 6 2 23 6 5 1 9 1


TABLE xLVI (next). The ichthyoregions and their repartition by country in Africa.

Non defined 3 (Namibia 1)

Non defined 4 (Namibia 2)
Non defined 2 (Abyssinia)

Lake Chilwa/Lago Chiuta
Non defined 1 (Red Sea)

Non defined 5 (Sahara)

Lake Edward/Édouard
Ichthyoregions

Lake Malawi/Nyasa

Lake Tanganyika
Lake Amaramba

Lake Malombe

Lake Naivasha

Lake Ruhondo
Lake Georges

Lake Victoria
Lake Rukwa
Lake Natron
Lake Kivu
Country

South Africa
Algeria 1
Angola
Benin
Botswana
Burkina Faso
Burundi 1 1
Cameroon
Central Africa
Congo
Congo DR / Zaïre 1 1 1
Côte d’Ivoire
Djibouti 1
Egypt 1 1 1
Erythrea 1
Ethiopia 1
Gabon
Gambia
Ghana
Guinea
Equatoriale Guinea
Guinea-Bissau
Kenya 1 1 1
Lesotho
Liberia
Libya 1
Madagascar
Malawi 1 1 1 1
Mali 1
Morocco 1
Mauritania 1
Mozambique 1 1 1
Namibia 1 1
Niger 1
Nigeria
Uganda 1 1 1 1
Rwanda 1 1 1
Western Sahara
Senegal
Sierra Leone
Somalia 1
Sudan 1 1
Swaziland
Tanzania 1 1 1 1 1
Chad 1
Togo
Tunisia 1
Zambia 1 1
Zimbabwe
Number of country 1 6 1 1 10 2 2 2 1 2 1 1 2 3 2 2 4 5


TABLE xLVII. The genera and species of tilapias recorded by countries.
N: Native; E: Endemic; I: Introduiced; ?: Not verified

Number of country

Equatoriale Guinea
Congo DR / Zaïre

Guinea-Bissau
Central Africa
Country

Total Length

Burkina Faso

Côte d’Ivoire
South Africa

Cameroon
Botswana
Species

Erythrea
Ethiopia

Lesotho
Burundi

Gambia
Djibouti

Guinea
Angola
Algeria

Gabon
Congo

Ghana

Kenya
Egypt
Benin
Number of species 106 48 7 2 13 7 8 3 6 30 3 11 27 18 0 8 2 10 10 7 11 12 3 10 22 1
Oreochromis amphimelas 31 1
Oreochromis andersonii 61 10 N N N I I
Oreochromis angolensis 23 1 E
Oreochromis aureus 46 11 I N I N
Oreochromis chungruruensis 23 1
Oreochromis esculentus 50 4 N
Oreochromis hunteri 34 2 N
Oreochromis ismailiaensis - 1 E
Oreochromis jipe 54 2 N
Oreochromis karomo 30 2
Oreochromis karongae 34 3
Oreochromis korogwe 31 2 N
Oreochromis lepidurus 19 2 N N
Oreochromis leucostictus 32 6 I N I
Oreochromis lidole 38 3
Oreochromis macrochir 40 25 I N I N I I I I I ? I I I I I
Oreochromis malagarasi 30 1
Oreochromis mortimeri 48 4 I ?
Oreochromis mossambicus 39 21 N I I I N I I I I I N
Oreochromis mweruensis 27 3 N
Oreochromis niloticus baringoensis 36 1 E
Oreochromis niloticus cancellatus 28 1 E
Oreochromis niloticus eduardianus 49 7 N N I
Oreochromis niloticus filoa 15 1 E
Oreochromis niloticus niloticus 64 34 I I N I N I I I N N I ? I N N N I
Oreochromis niloticus sugutae 20 1 E
Oreochromis niloticus tana 35 1 E
Oreochromis niloticus vulcani 28 2 N N
Oreochromis pangani girigan 33 1 E
Oreochromis pangani pangani 34 1
Oreochromis placidus placidus 36 4 N
Oreochromis placidus ruvumae 27 2
Oreochromis rukwaensis 36 1
Oreochromis saka 40 3
Oreochromis salinicola 10 1 E
Oreochromis schwebischi 33 4 N N N N
Oreochromis shiranus chilwae 20 2
Oreochromis shiranus shiranus 42 4
Oreochromis spilurus niger 35 4 N N
Oreochromis spilurus percevali 16 1 E
Oreochromis spilurus spilurus 19 6 I N N
Oreochromis squamipinnis 33 3
Oreochromis tanganicae 45 4 N N
Oreochromis upembae 23 2 N
Oreochromis urolepis hornorum 27 3 I
Oreochromis urolepis urolepis 48 1
Oreochromis variabilis 33 3 N


TABLE xLVII (next). The genera and species of tilapias recorded by countries.
N: Native; E: Endemic; I: Introduiced; ?: Not verified

Number of country
Country

Total Length

Mozambique

Sierra Leone
Madagascar

Zimbabwe
Mauritania

Swaziland
Morocco
Species

Tanzania
Namibia

Rwanda
Senegal

Somalie
Uganda

Zambia
Malawi

Nigeria

Tunisia
Liberia

Sudan
Libya

Chad
Niger

Togo
Mali
Oreochromis amphimelas 31 1 E
Oreochromis andersonii 61 10 N N I N N
Oreochromis angolensis 23 1
Oreochromis aureus 46 11 I N N N N N I
Oreochromis chungruruensis 23 1 E
Oreochromis esculentus 50 4 N I N
Oreochromis hunteri 34 2 N
Oreochromis ismailiaensis - 1
Oreochromis jipe 54 2 N
Oreochromis karomo 30 2 N N
Oreochromis karongae 34 3 N N N
Oreochromis korogwe 31 2 N
Oreochromis lepidurus 19 2
Oreochromis leucostictus 32 6 N I I
Oreochromis lidole 38 3 N N N
Oreochromis macrochir 40 25 I I ? N I I I I N N
Oreochromis malagarasi 30 1 E
Oreochromis mortimeri 48 4 N N
Oreochromis mossambicus 39 21 I N N I I ? N I I N
Oreochromis mweruensis 27 3 N N
Oreochromis niloticus baringoensis 36 1
Oreochromis niloticus cancellatus 28 1
Oreochromis niloticus eduardianus 49 7 N N I N
Oreochromis niloticus filoa 15 1
Oreochromis niloticus niloticus 64 34 N I N ? N N N I N N N I N N I I I
Oreochromis niloticus sugutae 20 1
Oreochromis niloticus tana 35 1
Oreochromis niloticus vulcani 28 2
Oreochromis pangani girigan 33 1
Oreochromis pangani pangani 34 1 E
Oreochromis placidus placidus 36 4 N N N
Oreochromis placidus ruvumae 27 2 N N
Oreochromis rukwaensis 36 1 E
Oreochromis saka 40 3 N N N
Oreochromis salinicola 10 1
Oreochromis schwebischi 33 4
Oreochromis shiranus chilwae 20 2 N N
Oreochromis shiranus shiranus 42 4 I N N N
Oreochromis spilurus niger 35 4 I I
Oreochromis spilurus percevali 16 1
Oreochromis spilurus spilurus 19 6 I N N
Oreochromis squamipinnis 33 3 N N N
Oreochromis tanganicae 45 4 N N
Oreochromis upembae 23 2 N
Oreochromis urolepis hornorum 27 3 N N
Oreochromis urolepis urolepis 48 1 E
Oreochromis variabilis 33 3 N N


N: Native
E: Endemic
I: Introduiced
?: Not verified

Number of country

Equatoriale Guinea
Congo DR / Zaïre

Guinea-Bissau
Central Africa
Country

Total Length

Burkina Faso

Côte d’Ivoire
South Africa

Cameroon
Botswana
Species

Erythrea
Ethiopia

Lesotho
Burundi

Gambia
Djibouti

Guinea
Angola
Algeria

Gabon
Congo

Ghana

Kenya
Egypt
Benin
Tilapia bakossiorum 9 1 E
Tilapia baloni 18 2 N
Tilapia bemini 9 1 E
Tilapia bilineata 18 1 E
Tilapia brevimanus 27 6 N N N N
Tilapia busumana 21 2 N N
Tilapia buttikoferi 41 4 N N
Tilapia bythobates 16 1 E
Tilapia cabrae 37 4 N N N N
Tilapia cameronensis 14 1 E
Tilapia cessiana 24 2 N
Tilapia coffea 19 1
Tilapia congica 25 1 E
Tilapia dageti 40 10 N N N N
Tilapia deckerti 20 1 E
Tilapia discolor 23 2 N N
Tilapia flava 12 1 E
Tilapia guinasana 14 2 I
Tilapia guineensis 35 17 N N N N N N N N N N N
Tilapia gutturosa 9 1 E
Tilapia imbriferna 15 1 E
Tilapia ismailiaensis ? 1 E
Tilapia jallae 8 1
Tilapia joka 11 2
Tilapia kottae 15 1 E
Tilapia louka 25 4 N N
Tilapia margaritacea 18 1 E
Tilapia mariae 40 5 N N N N
Tilapia nyongana 21 2 N N
Tilapia rendalli 45 24 N N N I N N N I N I
Tilapia rheophila 10 1 E
Tilapia ruweti 11 6 N N N
Tilapia snyderae 5 1 E
Tilapia sparrmanii 24 10 N N N
Tilapia spongotroktis 15 1 E
Tilapia tholloni 22 4 N N N N
Tilapia thysi 9 1 E
Tilapia walteri 27 2 N
Tilapia zillii 27 28 N N N N N N I I N N N N N


N: Native
E: Endemic
I: Introduiced
?: Not verified

Number of country
Country

Total Length

Mozambique

Sierra Leone
Madagascar

Zimbabwe
Mauritania

Swaziland
Morocco
Species

Tanzania
Namibia

Rwanda
Senegal

Somalie
Uganda

Zambia
Malawi

Nigeria

Tunisia
Liberia

Sudan
Libya

Chad
Niger

Togo
Mali
Tilapia bakossiorum 9 0
Tilapia baloni 18 1 N
Tilapia bemini 9 0
Tilapia bilineata 18 0
Tilapia brevimanus 27 2 N N
Tilapia busumana 21 0
Tilapia buttikoferi 41 2 N N
Tilapia bythobates 16 0
Tilapia cabrae 37 0
Tilapia cameronensis 14 0
Tilapia cessiana 24 1 N
Tilapia coffea 19 1 E
Tilapia congica 25 0
Tilapia dageti 40 6 N N N N N N
Tilapia deckerti 20 0
Tilapia discolor 23 0
Tilapia flava 12 0
Tilapia guinasana 14 1 N
Tilapia guineensis 35 6 N ? N N N N
Tilapia gutturosa 9 0
Tilapia imbriferna 15 0
Tilapia ismailiaensis ? 0
Tilapia jallae 8 1 E
Tilapia joka 11 2 N N
Tilapia kottae 15 0
Tilapia louka 25 2 N N
Tilapia margaritacea 18 0
Tilapia mariae 40 1 N
Tilapia nyongana 21 0
Tilapia rendalli 45 14 I N ? N N N I I N N N N N N
Tilapia rheophila 10 0
Tilapia ruweti 11 3 N N N
Tilapia snyderae 5 0
Tilapia sparrmanii 24 7 I N N N N N N
Tilapia spongotroktis 15 0
Tilapia tholloni 22 0
Tilapia thysi 9 0
Tilapia walteri 27 1 N
Tilapia zillii 27 15 N I N N N N N N N N N I N N N


N: Native
E: Endemic
I: Introduiced
?: Not verified

Number of country

Equatoriale Guinea
Congo DR / Zaïre

Guinea-Bissau
Central Africa
Country

Total Length

Burkina Faso

Côte d’Ivoire
South Africa

Cameroon
Botswana
Species

Erythrea
Ethiopia

Lesotho
Burundi

Gambia
Djibouti

Guinea
Angola
Algeria

Gabon
Congo

Ghana

Kenya
Egypt
Benin
Sarotherodon caroli 22 1 E
Sarotherodon caudomarginatus 20 4 N N
Sarotherodon galilaeus galilaeus 41 20 N N N N N N N N N N N
Sarotherodon galilaeus multifasciatus 17 2 N N
Sarotherodon galileus borkuanus 16 1
Sarotherodon galileus boulengeri 20 1 E
Sarotherodon galileus sanagaensis 16 2 N E
Sarotherodon linnellii 21 1 E
Sarotherodon lohbergeri 14 1 E
Sarotherodon melanotheron heudelotii 26 5 N N N
Sarotherodon melanotheron leonensis 20 2
Sarotherodon melanotheron melanotheron 26 14 N N N N N N N N
Sarotherodon melanotheron paludinosus 15 1
Sarotherodon mvogoi 24 3 N N N
Sarotherodon nigripinnis dolloi 22 3 N N N
Sarotherodon nigripinnis nigripinnis 20 4 N N N N
Sarotherodon occidentalis 31 5 N N
Sarotherodon steinbachi 15 1 E
Sarotherodon tournieri liberiensis 20 1
Sarotherodon tournieri tournieri 13 2 N
Alcolapia alcalicus 10 2 N
Alcolapia grahami 20 2 N
Alcolapia latilabris 9 1
Alcolapia ndalalani 8 1
Danakilia franchettii 10 1 E
Konia dikume 14 1 E
Konia eisentrauti 10 1 E
Myaka myaka 9 1 E
Pungu maclareni 14 1 E
Stomatepia mariae 15 1 E
Stomatepia mongo 14 1 E
Stomatepia pindu 13 1 E
Genera
Oreochromis 43 5 2 6 2 4 2 5 3 2 4 14 5 5 1 7 3 1 2 1 19 1
Tilapia 43 2 6 3 4 1 1 19 1 3 8 9 2 1 2 5 3 6 6 2 5 2
Sarotherodon 26 1 2 8 4 5 4 1 1 2 3 3 5 1 5 1
Alcolapia 2 2
Danakilia 1 1
Konia 1 2
Myaka 1 1
Pungu 1 1
Stomatepia 1 3


N: Native
E: Endemic
I: Introduiced
?: Not verified

Number of country
Country

Total Length

Mozambique

Sierra Leone
Madagascar

Zimbabwe
Mauritania

Swaziland
Morocco
Species

Tanzania
Namibia

Rwanda
Senegal

Somalie
Uganda

Zambia
Malawi

Nigeria

Tunisia
Liberia

Sudan
Libya

Chad
Niger

Togo
Mali
Sarotherodon caroli 22 0
Sarotherodon caudomarginatus 20 2 N N
Sarotherodon galilaeus galilaeus 41 9 N N N N N N N N N
Sarotherodon galilaeus multifasciatus 17 0
Sarotherodon galileus borkuanus 16 1 E
Sarotherodon galileus boulengeri 20 0
Sarotherodon galileus sanagaensis 16 0
Sarotherodon linnellii 21 0
Sarotherodon lohbergeri 14 0
Sarotherodon melanotheron heudelotii 26 2 N N
Sarotherodon melanotheron leonensis 20 2 N N
Sarotherodon melanotheron melanotheron 26 6 N N N N N N
Sarotherodon melanotheron paludinosus 15 1 E
Sarotherodon mvogoi 24 0
Sarotherodon nigripinnis dolloi 22 0
Sarotherodon nigripinnis nigripinnis 20 0
Sarotherodon occidentalis 31 3 N N N
Sarotherodon steinbachi 15 0
Sarotherodon tournieri liberiensis 20 1 E
Sarotherodon tournieri tournieri 13 1 N
Alcolapia alcalicus 10 1 N
Alcolapia grahami 20 1 N
Alcolapia latilabris 9 1 E
Alcolapia ndalalani 8 1 E
Danakilia franchettii 10 0
Konia dikume 14 0
Konia eisentrauti 10 0
Myaka myaka 9 0
Pungu maclareni 14 0
Stomatepia mariae 15 0
Stomatepia mongo 14 0
Stomatepia pindu 13 0
Genera
Oreochromis 43 9 3 2 2 1 3 2 4 3 4 2 1 4 6 1 2 3 3 3 1 4 3
Tilapia 43 6 1 1 3 1 2 5 4 1 2 2
Sarotherodon 26 4
Alcolapia 2
Danakilia 1
Konia 1
Myaka 1
Pungu 1
Stomatepia 1


Appendix 05
FILE OF SPECIES

Are presented here by files, different species more or less commonly in aquaculture. The reader
will find the scientific Synonyms, common names french and english, size and maximum weight
known in the literature, as well as distribution maps and elements of the biology of these species.

File I. Cichlidae. - Oreochromis andersoni 256

File II. Cichlidae. - Oreochromis aureus 257

File III. Cichlidae. - Oreochromis esculentus 258

File IV. Cichlidae. - Oreochromis macrochir 259

File V. Cichlidae. - Oreochromis mossambicus 260

File VI. Cichlidae. - Oreochromis niloticus 261

File VII. Cichlidae. - Oreochromis shiranus 262

File VIII. Cichlidae. - Sarotherodon galileus 263

File IX. Cichlidae. - Sarotherodon melanotheron 264

File X. Cichlidae. - Tilapia guineensis 265

File XI. Cichlidae. - Tilapia mariae 266

File XII. Cichlidae. - Tilapia rendalli 267

File XIII. Cichlidae. - Tilapia zillii 268

File XIV. Cichlidae. - Hemichromis elongatus and Hemichromis fasciatus 269

File XV. Cichlidae. - Serranochromis angusticeps 270

File XVI. Cichlidae. - Serranochromis robustus 271

File XVII. Clariidae. - Clarias gariepinus 272

File XVIII. Clariidae. - Heterobranchus longifilis 273

File XIX. Arapaimidae. - Heterotis niloticus 274


FILE I. CICHLIDAE.

Oreochromis andersoni (Castelnau, 1861)
Synonyms: Chromys andersoni Castelnau, 1861 - Oreochromis anulerson (Castelnau, 1861) - Sa-
rotherodon andersoni (Castelnau, 1861) - Tilapia andersoni (Castelnau, 1861) - Tilapia kafuensis
Boulenger, 1912 - Tilapia natalensis (non Weber)

English name: Three spotted tilapia Nom français:

© K. Winnemiller

Aquaculture: commercial Fishery: commercial - sport Ornemental:

Max. size: 61 cm TL

Max. weight: 4.7 kg

Biology: Benthopelagic. May
be found in brackish water. Oc-
curs in both river and swamp
habitats and is adapted to fairly
fast-flowing rivers, preferring
slow-flowing or standing wa-
ter; juveniles remain inshore
among vegetation. Forms scho-
ols. Mainly diurnal; a detritivore
which feeds on fine particulate
matter, including algae, diatoms,
detritus and zooplankton. Lar-
ger individuals also take insects
and other invertebrates. Female
mouthbrooder. Several countries
report adverse ecological impact
after introduction.

Distribution: Know from Ngami basin, Okavango River; Cunene River and Mossamedes, Angola;
upper Zambezi, Kafue River; middle Zambezi, Lake Kariba.


FILE II. CICHLIDAE.

Oreochromis aureus (Steindachner, 1864)
Synonyms: Chromis aureus Steindachner, 1864 - Tilapia aurea (Steindachner, 1864): Trewavas,
1966 - Sarotherodon aureus (Steindachner, 1864): Trewavas, 1973 – Tilapia monodi Daget, 1954 -
Tilapia lemassoni Blache & Miton, 1960

English name: Blue tilapia French name: Tilapia bleu

© Fishbase

Aquaculture: commercial Fishery: commercial - bait Ornemental: commercial

Max. size: 50.8 cm TL – 37 SL

Max. weight: 2.0 kg

Biology: Benthopelagic. Maybe
found in brackinsh water. Occu-
ring at temperatures ranging from
8°-30°C. Considered as a pest.
Forms schools; is sometimes ter-
ritorial; inhabits warm ponds and
impoundments as well as lakes
and streams, in open water as
well as among stones and vege-
tation. Feeds on phytoplankton
and small quantities of zooplank-
ton. Juveniles have a more varied
diet. Maternal mouthbrooder

Distribution: The natural distribution of this species include the Jordan Valley, Lower Nile, Chad
Basin, Benue, middle and upper Niger, Senegal River.


FILE III. CICHLIDAE.

Oreochromis esculentus (Graham, 1928)
Synonyms: Tilapia esculenta Graham, 1928 - Sarotherodon esculentus (Graham, 1928) - Tilapia
eduardiana (non Boulenger, 1912) - Tilapia galilaea (non Linnaeus, 1758) - Tilapia variabilis (non
Boulenger, 1906)

English name: Singida tilapia French name:

© Fishbase

Aquaculture: commercial Fishery: commercial - experimental Ornemental:

Max. size: 50 cm LS

Max. weight: 2.5 kg

Biology: Benthopelagic. Occurs
at temperatures ranging from
23.0-28.0°C. Tolerant of low oxy-
gen concentrations. Filter feeder.
Food consist almost entirely of
phytoplankton but also small ani-
mals such as insects and their
larvae, crustaceans. Maternal
moutbrooder.

Distribution: Known from Lake Victoria, Lake Nabugabo, Lakes Kyoga and Kwania, and the Vic-
toria Nile above the Murchison Falls; the Malawa River (Uganda) and Lake Gangu, west of Lake
Victoria. This species, which was originally endemic to Lake Victoria, is widely distributed in dams.


FILE IV. CICHLIDAE.

Oreochromis macrochir (Boulenger, 1912)
Synonyms: Tilapia galilaea (non Linnaeus) - Tilapia nilotica (non Linnaeus, 1758) - Chromys chapmani Castel-
nau, 1861 - Tilapia andersonii (non Castelnau, 1861) - Chromys chapmannii Castelnau, 1861 - Chromys spar-
manni Castelnau, 1861 - Tilapia squamipinnis (non Günther, 1864) - Tilapia natalensis (non Weber, 1897) - Tila-
pia macrochir Boulenger, 1912 - Loruwiala macrochir (Boulenger, 1912) - Sarotherodon macrochirus (Boulenger,
1912) - Oreochromis microchir (Boulenger, 1912) - Tilapia macrochir Boulenger, 1912 - Sarotherodon macrochir
(Boulenger, 1912) - Tilapia kafuensis (non Boulenger, 1912) - Tilapia intermedia Gilchrist & Thompson, 1917 - Ti-
lapia sheshekensis Gilchrist & Thompson, 1917 - Tilapia alleni Fowler, 1931

English name: Longfin, Greenhead tilapia French name: Tilapia noir

© Luc De Vos

Aquaculture: commercial Fishery: commercial - sport Ornemental:

Max. size: 43.0 cm SL

Max. weight:

Biology: Benthopelagic. Mating
territory having a central volca-
no-shaped mound. Prefers quiet,
deep water associated with
aquatic vegetation. Occasionally
forms schools, is mainly diurnal.
Feeds mostly on detritus, (blue-
green) algae and diatoms. Mater-
nal mouthbrooder.

Distribution: Known from Kafue, upper Zambezi, and Congo River systems; introduced elsewhere
in Africa and in Hawaiian Islands. Also in the Okavango and Ngami region, Cunene basin, Cham-
bezi and Bangweulu region.


FILE V. CICHLIDAE.

Oreochromis mossambicus (Peters, 1852)
Synonyms: Chromis mossambicus, Peters, 1852 - Tilapia arnoldi Gilchrist & Thompson, 1917 - Tilapia ka-
fuensis (non Boulenger, 1912) - Chromis niloticus (non Linneaus, 1758) - Tilapia mossambica (Peters, 1852)
- Sarotherodon mossambicus (Peters, 1852) - Chromis niloticus mossambicus Peters, 1855 - Chromis dumerilii
Steindachner, 1864 - Tilapia dumerilii (Steindachner, 1864) - Chromis vorax Pfeffer, 1893 - Tilapia vorax (Pfeffer,
1893) - Chromis natalensis Weber, 1897 - Tilapia natalensis (Weber, 1897) - Sarotherodon mossambicus nata-
lensis (Weber, 1897)

English name: Mozambic tilapia French name: Tilapia du Mozambique

© A. Lamboj

Aquaculture: commercial Fishery: commercial - sport Ornemental: commercial

Max. size: 39 cm SL

Max. weight: 1.1 kg

Biology: Benthopelagic. Highly
euryhaline. Grows and repro-
duces in fresh-, brackish and
seawater. Tolerates low dissolved
oxygen levels. Considered as a
pest. Can be found in quite all
kinds of habitat. Form schools.
Omnivorous, feeds mainly on al-
gae and phytoplankton but also
takes some zooplankton, small
insects and their larvae. Juvenile
carnivorous/omnivorous, adult
tends to be herbivorous or detri-
tus feeder. Large specimen has
been reported to prey on small
fishes. Maternal mouthbrooder.

Distribution: The natural distribution is of Lower Zambezi, Lower Shire and coastal plains from
Zambezi delta to Algoa Bay. Occurs southwards to the Brak River in the eastern Cape and in the
Transvaal in the Limpopo system. Widely introduced for aquaculture.


FILE VI. CICHLIDAE.

Oreochromis niloticus (Linneaus, 1758)
Synonyms: Labrus niloticus Linnaeus, 1758 - Chromis niloticus Günther, 1862 - Tilapia nilotica
(Linnaeus, 1758) - Sarotherodon niloticus (Linnaeus, 1758)

English name: Nile tilapia French name: Tilapia du Nil

© Y. Fermon

Aquaculture: commercial Fishery: commercial Ornemental: commercial

Max. size: 74 cm TL – 39.5 SL

Max. weight: 4.3 kg

Biology: Benthopelagic. Consi-
dered as a pest. Found in all kind
of habitats. Diurnal. Feed on phy-
toplankton and algae. Maternal
mouthbrooder.

8 sub-species of Oreochromis
niloticus are recorded:
O. n. baringoensis, O. n. cancel-
latus, O. n. eduardianus, O. n.
filoa, O. n. niloticus, O. n. sugu-
tae, O. n. tana, O. n. vulcani.
Distribution: O. n. niloticus: coastal rivers of Israel; Nile from below Albert Nile to the delta; Jebel
Marra; basins of the Niger, Benue, Volta, Gambia, Senegal and Chad. - O. n. baringoensis: en-
demic to Lake Baringo, Kenya. O. n. cancellatus: Lakes of the Ethiopian Rift Valley, Lake Beseka
and the Awash system. O. n. edouardianus: Albert Nile; Lakes Albert, Edward, George, Kivu; River
Ruzizi and Lake Tanganyika. Introduced in Lake Victoria. O. n. filoa: Awash system. O. n. sugutae:
river Suguta in Kenya. O. n. tana: Lake Tana. O. n. vulcani: Lake Turkana (Rudolf) and arround.


FILE VII. CICHLIDAE.

Oreochromis shiranus Boulenger, 1897
Synonyms: Sarotherodon shiranus (Boulenger, 1897) - Sarotherodon shiranus subsp. shiranus
(Boulenger, 1897) - Tilapia placida (non Trewavas, 1941) - Tilapia shirana (Boulenger, 1897) - Tilapia
shirana subsp. chilwae Trewavas, 1966 - Tilapia shirana subsp. shirana (Boulenger, 1897)

English name: French name:

© Fishbase


Max. size: 39 cm SL

Max. weight:

Biology: Benthopelagic. Found
mainly in densely vegetated
shallow waters around the lake
Malawi. Mainly diurnal; feeds on
detritus and phytoplankton. Ma-
ternal mouthbrooder.

2 sub-species of Oreochromis
shiranus are recorded:
O. s. shiranus, O. s. chilwae
Distribution: O. s. shiranus: Shire River above the Murchison rapids and its tributaries; Lake Ma-
lawi and its tributary rivers, streams and lagoons; upper Shire.
O. s. chilwae: Lake Chilwa and its basin in Malawi and Mozambique.


FILE VIII. CICHLIDAE.

Sarotherodon galileus (Linneaus, 1758)
Synonyms: Sparus galilaeus Linnaeus, 1758 - Tilapia galilaea (Linnaeus, 1758) - Tilapia galilaea ga-
lilaea (Linnaeus, 1758) - Tilapia pleuromelas Duméril, 1859 - Tilapia lateralis Duméril, 1859 - Tilapia
macrocentra Duméril, 1859 - Chromis multifasciatus Günther, 1903 - Tilapia multifasciata (Günther,
1903) - Tilapia galilaea multifasciata (Günther, 1903)

English name: Mango tilapia French name:

© Fishbase

Aquaculture: commercial Fishery: commercial Ornemental:

Max. size: 41 cm TL – 34 SL

Max. weight: 1.6 kg

Biology: Demersal. Occasionally
forms schools; territorial. Prefers
open waters but juveniles and
breeding adults are found ins-
hore Feeds on algae and fine or-
ganic debris. Bi-parental mouth-
brooder.

5 sub-species of Sarotherodon
galileus are recorded:
S. g. borkuanus, S. g. boulengeri,
S. g. galileus, S. g. multifasciatus,
S. g. sanagaensis.
Distribution: S. g. borkuanus: Saharian oases Borku, Ennedi and Tibesti in northern Chad. S. g. boulengeri:
Lower Congo from Malebo (Stanley) Pool to Matadi. S. g. galileus: Jordan system, especially in lakes; coastal
rivers of Israel; Nile system, including the delta lakes and Lake Albert and Turkana; central Congo basin, Uban-
ghi and Uele Rivers; in West Africa in the Senegal, Gambia, Casamance, Géba, Konkouré, Niger, Volta, Mono,
Ouémé, Ogun, Cross, Benue, Logone, Shari and Lake Chad. S. g. multifasciatus: Côte d’Ivoire (Sassandra,
Bandama, and Comoé Rivers) to western Ghana (Tano River and Lake Bosumtwi). S. g. sanagaensis: known only
from the Sanaga River system, Cameroon.


FILE Ix. CICHLIDAE.

Sarotherodon melanotheron Rüppel, 1852
Synonyms: Tilapia heudelotii Duméril, 1859 - Tilapia heudelotii heudelotii Duméril, 1859 - Tilapia
rangii Duméril, 1859 - Tilapia multifasciata macrostoma Pellegrin, 1941 - Sarotherodon melanothe-
ron paludinosus Trewavas, 1983 - Tilapia melanotheron (Rüppell, 1852) - Chromis microcephalus
Günther, 1862 - Tilapia microcephala (Günther, 1862) - Melanogenes macrocephalus Bleeker, 1862
- Tilapia macrocephala (Bleeker, 1862) - Tilapia leonensis Thys van den Audenaerde, 1971

English name: Blackchin tilapia French name: Tilapia à gorge noire

© Y. Fermon


Max. size: 31 cm TL

Max. weight:

Biology: Demersal. Primarily in
estuaries and lagoons. Abundant
in mangrove areas. Potential
pest. Forms schools; is mainly
nocturnal with intermittent day-
time feeding. Feeds on aufwuchs
and detritus.

3 sub-species of Sarotherodon
melanotheron are recorded:
S. m. heudelotii, S. m. melano-
theron, S. m. leonensis.
Distribution: S. m. heudelotii: Lagoons and estuaries from Mauritania to Sierra Leone.
S. m. melanotheron: Lagoons and estuaries from Côte d’Ivoire to Cameroon.
S. m. leonensis: brackish areas and freshwaters near the coast of Sierra Leone and western Libe-
ria. Sometimes found in sea.


FILE x. CICHLIDAE.

Tilapia guineensis (Bleeker in Günther, 1862)
Synonyms: Chromis guineensis Bleeker in Günther, 1862 - Haligenes guineensis Bleeker, 1863
- ?Tilapia affinis Duméril,1858 - ?Chromis latus Günther, 1862 - ?Tilapia lata (Günther, 1862) - ?Ti-
lapia polycentra Duméril, 1858

English name: Guinea tilapia French name: Tilapia de Guinée, Carpe

© A. Lamboj

Aquaculture: commercial Fishery: commercial Ornemental:

Max. size: 35 cm TL - 28.2 SL

Max. weight:

Biology: Found also in brackish
waters. Benthopelagic. Feeds on
shrimps, bivalves, plankton and
detritus. Oviparous. Substrate
spawner.

Distribution: Known from coastal waters from mouth of Senegal River to mouth of the Cuanza
River (Angola), sometimes ascending far up rivers.


FILE xI. CICHLIDAE.

Tilapia mariae Boulenger, 1899
Synonyms: Tilapia dubia Lönnberg, 1904 - Tilapia heudeloti (non Duméril, 1861) - Tilapia mariae
dubia Lönnberg, 1904 - Tilapia meeki Pellegrin, 1911 - Tilapia melanopleura (non Duméril, 1861) -
Tilapia microcephala (non Günther, 1862)

English name: Spotted tilapia French name: Tilapia à 5 bandes

© Fishbase

Aquaculture: Fishery: Ornemental: commercial

Max. size: 39.4 cm TL - 23 SL

Max. weight: 1.4 kg

Biology: Demersal. May be found
in brackish water. Considered
as a pest. Live in still or flowing
waters in rocky or mud-bottom
areas. Consume plant matter.
Reache sexual maturity at 10-
15 centimeters length. Parents
prepare nest site on logs, leaves
and other debris. The eggs (600-
3300 per female) are guarded
by the parents and hatch in 1-3
days. Parental care of the brood
continues until the fish are about
2.5-3.0 centimeters. Substrate
spawner.

Distribution: Known from coastal lagoons and lower river courses from the Tabou River (Côte
d’Ivoire) to the Kribi River (Cameroon), but absent from the area between the Pra River (Ghana)
and Benin.


FILE xII. CICHLIDAE.

Tilapia rendalli (Boulenger, 1897)
Synonyms: Chromis rendallii Boulenger, 1896 – Tilapia sexfasciata Pellegrin, 1900 – Tilapia latifrons Boulenger,
1906 –Tilapia christyi Boulenger, 1915 – Tilapia druryi Gilchrist & Thompson, 1917 – Tilapia kirkhami Gilchrist &
Thompson, 1917 – Tilapia mackeani Gilchrist & Thompson, 1917 – Tilapia sykesii Gilchrist & Thompson, 1917 –
Tilapia swierstrae Gilchrist & Thompson, 1917 – Tilapia gefuensis Thys van den Audenaerde, 1964 –Tilapia zillii
(non Gervais, 1848) - Tilapia melanopleura rendalli (Boulenger, 1897) - Tilapia melanopleura (non Duméril, 1861)
- Tilapia lata (non Günther, 1862) - Tilapia melanopleura swierstrae Gilchrist & Thompson, 1917
English name: Redbreasted tilapia French name: Tilapia à poitrine rouge, carpe

© Fishbase © Fishbase


Max. size: 45 cm TL

Max. weight: 2.5 kg

Biology: Demersal. Considered
as a pest. Prefer quiet, well-ve-
getated water along river littorals
or backwaters, floodplains and
swamps. Form schools; is mainly
diurnal. Juveniles feed on plank-
ton. Adults feed mainly on higher
plants and also algae, insects
and crustaceans. Tolerant of a
wide range of temperature and
salinity.

Distribution: Know from Senegal and Niger River, Congo River system, Zambezi River system,
Lake Tanganyika and Malagarazi. Also known from Shaba, upper Kasaï, Lualaba system, Lake
Malawi, Natal, Okavango and Cunene. Introduced elsewhere.


FILE xIII. CICHLIDAE.

Tilapia zillii (Gervais, 1848)
Synonyms: Acerina zillii Gervais, 1848 - Haligenes tristrami Günther, 1859 - Tilapia melanopleura
Duméril, 1859 - Chromis andreae Günther, 1864 - Chromis caeruleomaculatus de Rochebrune,
1880 - Chromis faidherbii de Rochebrune, 1880 - Chromis menzalensis Mitchell, 1895 - Tilapia
sparrmani multiradiata Holly, 1928 - Tilapia shariensis Fowler, 1949

English name: Redbelly tilapia French name: Tilapia à ventre rouge

© A. Lamboj


Max. size: 49 cm TL - 21 SL

Max. weight:

Biology: Demersal. Occasionally
form schools; mainly diurnal.
Prefer shallow, vegetated areas.
Fry are common in marginal ve-
getation and juveniles are found
in the seasonal floodplain. Herbi-
vorous. Substrate spawner.

Distribution: Found is South Morocco, Sahara, Niger-Benue system, rivers Senegal, Sassandra,
Bandama, Boubo, Mé, Comoé, Bia, Ogun and Oshun, Volta system, Chad-Shari system, Ubangi-
Uele-Ituri Rivers (Democratic Republic of the Congo), Lakes Mobutu and Turkana, Nile system and
the Jordan system. Introduced in several countries.


FILE xIV. CICHLIDAE.

Hemichromis « vert »: H. fasciatus Peters, 1852 - H. elongatus (Guichenot, 1861)
This group included several species but request more taxonomic investigations. Two main
species which are regularly confused: H. fasciatus and H. elongatus.
Synonyms: H. fasciatus: H. leiguardii Capello, 1872 - ?Hemichromis desguezii de Rochebrune,
1880 - Hemichromis frempongi Loiselle, 1979. H. elongatus: Hemichromis auritus Gill, 1962
English name: Banded jewelfish French name: Hemichromis rayé

© A. Lamboj

Aquaculture: commercial Fishery: subsistence Ornemental: commercial

Max. size: 25 cm TL - 20.4 SL

Max. weight: 0.3 kg

Biology: Benthopelagic. Pota-
modromous. Found in savan-
nah and forests. Feeds on fish,
shrimp and aquatic insects; very
aggressive and territorial. Subs-
trate spawner.

Distribution: H. fasciatus (in blue on the map). Found from the Nile basin to the East and in Central
regions as Lake Chad. Widely distributed from Senegal to Congo.
H. elongatus (in red on the map). Found from Sierra Leone to Okavango and Zambezi basins.


FILE xV. CICHLIDAE.

Serranochromis angusticeps (Boulenger, 1907)
Synonyms: Chromys levaillantii Castelnau, 1861- Serranochromis levaillantii (Castelnau, 1861)
- Tilapia levaillantii (Castelnau, 1861) - Paratilapia robusta (non Günther, 1864) - Paratilapia an-
gusticeps Boulenger, 1907 - Paratilapia kafuensis Boulenger, 1908 - Serranochromis kafuensis
(Boulenger, 1908)

English name: Thinface largemouth French name:

© K. Winnemiller


Max. size: 41 SL

Max. weight: 2.5 kg

Biology: Demersal. Occurs in
well-vegetated swamps and
along the edges of rivers. Also
occurs in fast-flowing reaches
over sand and rocks. Feeds on
small fish, shrimps and insects. A
mouthbrooding species.

Distribution: Cunene River system, Okavango River, upper Zambezi, and Kafue Rivers, and Lua-
pula-Moeru.


FILE xVI. CICHLIDAE.

Serranochromis robustus (Günther, 1864)
Synonyms: Chromys levaillantii Castelnau, 1861- Serranochromis levaillantii (Castelnau, 1861)
- Tilapia levaillantii (Castelnau, 1861) - Paratilapia robusta (non Günther, 1864) - Paratilapia an-
gusticeps Boulenger, 1907 - Paratilapia kafuensis Boulenger, 1908 - Serranochromis kafuensis
(Boulenger, 1908)

English name: Yellow-belly bream French name:

© K. Winnemiller

Aquaculture: Fishery: commercial - sport Ornemental:

Max. size: 56 TL

Max. weight: 6.1 kg

Biology: Demersal. Found over
sandy and vegetated areas as
well as over rocky substrates.
Feeds on fish and sand-dwel-
ling invertebrates (Ref. 5595).
Larger specimens prefer deep
main channels and permanent
lagoons, whereas smaller fishes
occur mainly in lagoons and se-
condary channels. Oviparous.
Breeds in summer, nesting along
vegetated fringes of mains-
treams. Mouthbrooder.

2 sub-species of Serranochro-
mis robustus are recorded:
S. r. robustus, S. r. jallae.
Distribution: S. r. robustus: Found in Lake Malawi and the upper Shire River. Reported from
Luongo River, Congo system, Zambia. Translocated to the upper Ruo River in Malawi and also to
Swaziland.
S. r. jallae: Found in Cunene River, Okovango River, upper Zambezi River, Kafue River, middle Zam-
bezi River including the Luangwa River; Luapula-Moero, Lualaba and Kasai (Congo River system).
Translocated to localities in Zimbabwe, to the Limpopo River and Natal, South Africa.


FILE xVII. CLARIIDAE

Clarias (Clarias) gariepinus (Burchell, 1822)
Synonyms: Silurus (Heterobranchus) gariepinus Burchell, 1822 - Clarias syriacus Valenciennes, 1840 - Clarias capensis Valen-
ciennes, 1840 - Clarias lazera Valenciennes, 1840 - Clarias mossambicus Peters, 1852 - Clarias xenodon Günther, 1864 - Clarias
macracanthus Günther, 1864 - Clarias orontis Günther, 1864 - Clarias robecchii Vinciguerra, 1893 - Clarias microphthalmus Pfeffer,
1896 - Clarias smithii Günther, 1896 - Clarias guentheri Pfeffer, 1896 - Clarias micropthalmus Pfeffer, 1896 - Clarias longiceps Bou-
lenger, 1899 - Clarias moorii Boulenger, 1901 - Clarias vinciguerrae Boulenger, 1902 - Clarias tsanensis Boulenger, 1902 - Clarias
malaris Nichols & Griscom, 1917 - Clarias notozygurus Lönnberg & Rendahl, 1922 - Clarias depressus Myers, 1925 - Clarias muelleri
Pietschmann, 1939

English name: North African catfish French name: Silure, poisson-chat nord africain

© Y. Fermon

Aquaculture: commercial Fishery: commercial minor Ornemental:

Max. size: 170 TL

Max. weight: 60 kg

Biology: Benthopelagic. OOc-
curs mainly in quiet waters, but
be found quite everywherer. Wi-
dely tolerant of extreme environ-
mental conditions. The presence
of an accessory breathing organ
enables this species to breath
air, it can move from place to
place with its pectoral fins. Fo-
rages at night on a wide variety
of prey. Feeds on insects, plan-
kton, invertebrates and fish but
also takes young birds, rotting
flesh and plants. Migrates to ri-
vers and temporary streams to
spawn. It was noted to generate
weak electric discharges.

Distribution: Almost Pan-Africa, absent from Maghreb, the upper and lower Guinea and the Cape
province and probably also Nogal province. Asia: Jordan, Israel, Lebanon, Syria and southern
Turkey. Widely introduced to other parts of Africa, Europe and Asia. Several countries report ad-
verse ecological impact after introduction.


FILE xVIII. CLARIIDAE

Heterobranchus longifilis Valenciennes, 1840
Synonyms: Heterobranchus laticeps Peters, 1852 - Clarias loangwensis Worthington, 1933 - He-
terobranchus platycephalus Nichols & LaMonte, 1934

English name: Vundu French name: Silure, Vundu

© Y. Fermon

Aquaculture: commercial Fishery: commercial minor Ornemental: commercial

Max. size: 150 cm SL

Max. weight: 55 kg

Biology: Demersal. Occurs
in large deep rivers within the
mainstream or in deep pools
and lakes. Most active at night,
feeding on any available food, in-
cluding invertebrates and insects
when small, fish and other small
vertebrates when large.

Distribution: Found from Nile, Niger, Senegal, Congo system, upper and middle Zambezi. Also
from Lakes Tanganyika and Edward, Gambia and Benue River, Chad and Volta basins, and the
coastal basins of Guinea to Nigeria.


FILE xIx. ARAPAIMIDAE

Heterotis niloticus (Cuvier, 1829)
Synonyms: Clupisudis niloticus (Cuvier, 1829) - Sudis niloticus Cuvier, 1829 - Sudis nilotica
Cuvier, 1829 - Sudis adansonii Cuvier, 1829 - Heterotis nilotica (Cuvier, 1829) - Heterotis adansonii
(Cuvier, 1829) - Heterotis ehrenbergii Valenciennes, 1847 - Heterotis adansoni Valenciennes, 1847

English name: African bonytongue, Heterotis French name: Poissons sans nom, Heterotis

© www.arowana.de


Max. size: 100 cm SL

Max. weight: 10.2 kg

Biology: Pelagic. Its auxiliary
branchial air breathing organs
enable it to survive in deoxyge-
nated waters. It feeds mostly
on plankton. During breeding, it
creates a circular nest in swamps.
The young leave the nest after a
few days and are guarded by the
male.

Distribution: In the case of this species, a distinction must be made between the present area of occurrence
resulting from man-made introductions, and its original, natural geographical distribution area. It is generally
accepted that the first introductions were made in the early fifties of this century. Original (natural) distribution:
all water-basins of the Nilo-Sudanese region: rivers Corubal, Senegal, Gambia, Volta, Niger (as well as Benue),
Chad, Nile, Omo and lake Turkana. Areas of successful introduction: artificial reservoirs of Côte d’Ivoire (Banda-
ma and Bia basins), rivers Cross, Sanaga, Nyong, Ogowe, Lower and Middle Congo (the species was apparently
unable to overcome the Kisangani falls), Ubangui and Kasaï. Attempts to implant the species in Madagascar
have generally been fruitless, although it may occur in certain river basins along the eastern coast of the island.


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