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    Application letter project development intern-kenya Application letter project development intern-kenya Document Transcript

    • ACF - INTERNATIONAL NET WORKThe subsistence fishfarmingin Africa: Technical Manual Yves FERMON In collaboration with: Aımara
    • Cover photos:Ö Top right: Tilapia zillii - © Anton LambojÖ Top left: Pond built by ACF in DRC, 2008 - © François CharrierÖ Bottom: Beneficiaries in front of the pond they have done, Liberia, ASUR, 2006 - © Yves Fermonii 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, theneeds for the populations and the already existing supply in fish. Then, a whole process is connectedinvolving the technical sides of the installation of fish ponds, follow-ups of the biological aspectsof the ponds. Finally, it is a question of managing and of carrying out a follow-up of the ponds andproduction 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 andwhat 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 ofintervention. But they are also a social and cultural development, with the beliefs and taboos, landissues and laws. The fact that, according the region of intervention, the ethnic and social groups andcountries, 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 ... haveprovided 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
    • ACRONYMSACF/AAH: Action Contre la Faim / Action Against HungerAIMARA: Association de spécialistes oeuvrant pour le développement et l’application des connaissances sur les poissons et les rela- tions Homme-NatureAPDRA-F: Association Pisciculture et Développement RuralASUR: Association d’Agronomie et Sciences Utiles à la Réhabilitation des populations vulnérablesCIRAD: Centre de coopération Internationale en recherche Agrono- mique pour le DéveloppementCNRS: Centre national de la recherche scientifiqueFAO: Food and Agriculture Organization of the United NationsIRD: Institut de Recherche pour le DéveloppementMNHN: Muséum national d’Histoire naturelleUNO: United Nation OrganisationNGO: Non Governemental OrganisationGIS: Geographic Informatic SystemBDC: Biological Diversity ConventionIBI: Integrity Biological IndiceDRC: 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.comvi Subsistence fishfarming in Africa
    • ACKNOWLEDGEMENTSÖ ACF Devrig VELLY - Senior Food Security advisor, AAH Cédric BERNARD - Food Security advisor in DRC, AAH François CHARRIER - Food Security advisor in DRC, AAH, RereaderÖ Aimara François MEUNIER - Emeritas Professor at MNHN, President of AIMA- RA, Rereader Patrice PRUVOST - Secretary of AIMARA Hélène PAGÉZY - Researcher, CNRSÖ 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 40viii Subsistence fishfarming in Africa
    • V.2. The relations man-resources 40 V.3. The relations man-man 41Chapter 05 - VILLAGES AND SITES SELECTIONS 43I. THE VILLAGES SELECTION 43II. THE SITES SELECTION 45 II.1. The water 45 II.2. The soil 50 II.3. The topography 53 II.4. The other parameters 56Chapter 06 - CHARACTERISTICS OF THE PONDS 59I. DESCRIPTION 59II. TYPES OF PONDS 59 II.1. Barrage ponds 62 II.2. Diversion ponds 62 II.3. Comparison 62III. 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 69IV. SUMMARY 71Chapter 07 - THE CONSTRUCTION OF POND 73I. THE DESIGN PLAN 73II. THE CLEANING OF THE SITE 75III. WATER SUPPLY: WATER INTAKE AND CHANNEL 77IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE 81V. THE PICKETING OF THE POND 82VI. THE CONSTRUCTION OF THE DIKES 83VII. THE DEVELOPMENT OF THE PLATE (BOTTOM) 89VIII. 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 105Ix. 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 163x Subsistence fishfarming in Africa
    • I.5. Fight against predators 164 I.6. Summary 164II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION 165III. 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 171IV. PONDS AND HEALTH 171GENERAL SUMMARY 173REFERENCES 177GLOSSARY 179APPENDIx 187Appendix 01 - ExAMPLES OF FILES 189I. FILES FOR MONITORING THE PONDS 189II. FILES FOR THE FOLLOW-UP OF THE FISH 191Appendix 02 - TABLE OF DATA 193Appendix 03 - SOME ELEMENTS OF THE BIOLOGY OF THE SPECIES 207I. THE MORPHOLOGY AND THE SYSTEMATIC 207II. THE BIOLOGY OF CICHLIDAE 216 II.1. The taxonomy 216 II.2. The feeding habits 217 II.3. The reproduction and parental care 218III. 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 233IV. 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 237Appendix 04 - BIOGEOGRAPHIC DATA 239Appendix 05 - FILE OF SPECIES 255 Subsistence fishfarming in Africa xI
    • LIST OF FIGURES Part I - INTRODUCTION AND THEORICAL ASPECTS 1 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 Part II - PRACTICAL ASPECTS 27 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. 72xii Subsistence fishfarming in Africa
    • Figure 47. Setting of fish pond: 3. Ponds. 74Figure 48. Visualization by picketing of the first plan of possible water supply, possible drainage, of diffe- rents valley (CIRAD). 75Figure 49. Preparation of the site of the pond. 76Figure 50. Cleaning of the site. 76Figure 51. Water levels differences. 78Figure 52. Setting of the water supply channel. 79Figure 53. Transverse profile of the channel. Measure and slope of sides. 79Figure 54. Channel digging. 80Figure 55. Setting of draining channel. 81Figure 56. Level of draining channel. 81Figure 57. Picketing of the pond and the dikes. 82Figure 58. Cleaning of the zones where the dikes will be build. 83Figure 59. Definition of the different types of dikes. 83Figure 60. Description and proportion of a dike (of 1 m high). 83Figure 61. Pressure difference on a dike. 84Figure 62. Dikes. Good high; Dikes too small. 84Figure 63. Digging of the cut-off trench for clay core. 85Figure 64. Clay core and saturation of the dikes. 85Figure 65. High of a dike. Depth; Freeboard; Settlement. 85Figure 66. High of the structure. 85Figure 67. Dimension of a dike. 86Figure 68. Calculation of the slope of the dikes. 87Figure 69. Construction of the dikes (I). Traditionnal - By blocks. 88Figure 70. Construction the dikes (II). 88Figure 71. Preparation of the bottom. 88Figure 72. The bottom or plate. Direction of the slope and drain setting: In ray; As «fish bones». 89Figure 73. Bottom drain. 90Figure 74. Cross cut of a pond at the bottom drain. 90Figure 75. Cross cut of the inlet of a pond. 91Figure 76. Pipe inlet. 91Figure 77. End of bamboo pipe. 91Figure 78. Gutter inlet. 92Figure 79. Different types of gutter. 92Figure 80. Canal inlet. 92Figure 81. Diagram of an example of sand filter. 93Figure 82. Turn-down pipe inside pond outlet. 95Figure 83. Composition of a monk. 96Figure 84. Position of the monk in the pond. 97Figure 85. Position of the monk according the downstream dike. 97Figure 86. Wooden monk. Small and medium size. 98Figure 87. Wooden pipe. 99Figure 88. Mould of a monk. Front view; Upper view. 100Figure 89. Monk. Upper view and example of size. 101Figure 90. Functioning of a monk. 102Figure 91. Concrete pipe. Croos cut; Mould; Final pipe. 103Figure 92. Setting of a pipe overflow. 104Figure 93. Type of setting basin. Natural; In concrete. 105Figure 94. Setting basin. Normal; Improved. 106Figure 95. Setting of a vegetable cover on the dikes. 106Figure 96. Dikes with plants. Vegetable garden; Small animals; Trees. 107Figure 97. Type of erosion and soil conservation. Streaming; Infiltration; Protection channel. 107Figure 98. Fences. In scrubs; In wood or bamboo. 108Figure 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. 172xiv Subsistence fishfarming in Africa
    • APPENDIx 187Figure 152. Principal terms pertinent to the external morphology of a fish. 207Figure 153. Different body shapes. 207Figure 154. Cross-section of body. 208Figure 155. Jaws. 208Figure 156. Tooth shapes. 209Figure 157. Fontanellae. 209Figure 158. Barbels. 210Figure 159. Gill slits without opercule; gill arch formed by ceratobranchial, gill rakers, hypobranchial and epibranchial, gill filaments; external gill. 210Figure 160. Accessory aerial breathing organs. 211Figure 161. Pair fins. 211Figure 162. Dorsal fin. 212Figure 163. Caudal fin. 212Figure 164. Different types of scales. 213Figure 165. Lateral line. 213Figure 166. Location of electric organs. 213Figure 167. Principal measurements that may be taken on a fish. 215Figure 168. External features of the Cichlidae. 216Figure 169. Courtship and spawning in a substrate spawner Cichlidae, Tilapia zillii. 218Figure 170. Nest of Oreochromis niloticus; Oreochromis macrochir. 219Figure 171. Courtship and spawning in a mouthbrooder Cichlidae, Haplochromis burtoni from Lake Tanga- nyika. 220Figure 172. Mouthbrooding. 220Figure 173. Example of the life cycle of a maternal mouthbrooding tilapia. 221Figure 174. Different stages in mouthbrooders. 222Figure 175. Comparison between fry of substrate spawners and mouthbrooders. 222Figure 176. Relationship the weight of fish of 20 cm and the size of maturation for Oreochromis niloticus for several geographic location. 224Figure 177. Size class of Oreochromis niloticus according several geographic location. 224Figure 178. Comparison of growth rate for different species in natural field by locality. 225Figure 179. Comparison of growth rate for different species in natural field by species. 225Figure 180. Relative Fecundity (% of total weight), % of hatching (% total eggs) of Clarias gariepinus, monthly average rainfall and average temperature. Brazzaville. 227Figure 181. Courtship in Clarias gariepinus. 228Figure 182. First stages of development for Clarias gariepinus. 229Figure 183. Several stages of larval development until 17 days. Clarias gariepinus; Heterobranchus longifi- lis. 229Figure 184. Compared growth of several African fish species. 230Figure 185. Growth of Heterotis niloticus and of Lates niloticus. 238Figure 186. The ichthyoregions and the countries. 245 Subsistence fishfarming in Africa xV
    • LIST OF TABLES Part I - INTRODUCTION AND THEORICAL ASPECTS 1 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 Part II - PRACTICAL ASPECTS 27 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) 170xvi Subsistence fishfarming in Africa
    • APPENDIx 187Table XXXVIII. The tonnage of halieutic products in 2005 per African countries (FAO, 2006). 194Table XXXIX. The checklist of freshwater species which have been the subject of an introduction in Africa (FAO, 2006; Fishbase, 2006). 195Table XL. List of species introduced by African countries. 197Table XLI. List of freshwater fish used in aquaculture by country (FAO, 2006; Fishbase, 2008). 203Table XLII. Diet of several species of tilapia in natural waters. 217Table XLIII. Size at sexual maturation, maximale size and longevity of different species of tilapia. 223Table XLIV. Some characteristics of African countries. 240Table XLV. Characteristics of ichthyoregions and lakes in Africa. 244Table XLVI. The ichthyoregions and their repartition by country in Africa. 246Table XLVII. The genera and species of tilapias recorded by countries. 248 LIST OF SPECIES FILEFile I. Cichlidae. - Oreochromis andersoni 256File II. Cichlidae. - Oreochromis aureus 257File III. Cichlidae. - Oreochromis esculentus 258File IV. Cichlidae. - Oreochromis macrochir 259File V. Cichlidae. - Oreochromis mossambicus 260File VI. Cichlidae. - Oreochromis niloticus 261File VII. Cichlidae. - Oreochromis shiranus 262File VIII. Cichlidae. - Sarotherodon galileus 263File IX. Cichlidae. - Sarotherodon melanotheron 264File X. Cichlidae. - Tilapia guineensis 265File XI. Cichlidae. - Tilapia mariae 266File XII. Cichlidae. - Tilapia rendalli 267File XIII. Cichlidae. - Tilapia zillii 268File XIV. Cichlidae. - Hemichromis elongatus and Hemichromis fasciatus 269File XV. Cichlidae. - Serranochromis angusticeps 270File XVI. Cichlidae. - Serranochromis robustus 271File XVII. Clariidae. - Clarias gariepinus 272File XVIII. Clariidae. - Heterobranchus longifilis 273File XIX. Arapaimidae. - Heterotis niloticus 274 Subsistence fishfarming in Africa xVII
    • LIST OF PHOTOS Part I - INTRODUCTION AND THEORICAL ASPECTS 1 Part II - PRACTICAL ASPECTS 27 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]. 237xviii Subsistence fishfarming in Africa
    • Part IINTRODUCTION 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 25Cover photo:Ö Children fishing fingerlings in river for the ponds, Liberia, ASUR, 2006 - © Yves Fermon2 Subsistence fishfarming in Africa
    • Chapter 01FISHFARMING: AIM AND ISSUESI. 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 2.5billion 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 foodinsecurity - in Asia and Africa, for example - the fish proteins are essential because, they guarantee agood part of the already low level of needs of animal proteins. Approximately 97% of the fishermenlive in the developing countries, where fishing is extremely important. Fish production in Africa has stagnated over the past decade, and availability of fish per capitadecrease (8.8 kg in the 90s, about 7.8 kg in 2001) (Table I, p. 4). Africa is the only continent where thistendency is observed, and the problem is that there do not exist other sources of proteins accessibleto 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 inlandwater ecosystems are very productive and sustain important fisheries which recorded a rise in somecountries. With a production of 7.5 million tons in 2003 and similar levels in previous years, the fishensures 50% or more of the animal protein contributions of many Africans - i.e. the second rankafter 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 andmalnutrition. 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 theMillions tonnes140 China120 World excluding China100 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). Subsistence fishfarming in Africa 3
    • 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 of4 Subsistence fishfarming in Africa
    • 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). Subsistence fishfarming in Africa 5
    • 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 is6 Subsistence fishfarming in Africa
    • linked to industrial activities. If it is not clear to what extent and how fast will this warming, it may befeared that these climate changes occur in the coming decades, resulting in a change in rainfall insome 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 thedistribution of vegetation, at an elevation sea levels. Although it is still impossible at the local level toassess the consequences of the changes announced, it seems clear, whatever the magnitude of thephenomenon 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 atthe 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, theconstruction of locks for navigation ... are still limited in Africa, but we can nevertheless give someexamples of projects that have changed quite considerably natural systems. In the valley of Senegal, for example, many work was completed for better managing the waterresources of the river and to use them at agricultural ends. The purpose of the construction of adam downstream nearby the estuary (dam Diama) is to prevent the coming back of marine water inthe lower course of the river during the dry season, whereas the dam Manantali located upstreammakes it possible to store great quantities of water at the time of the overflood and to restore themaccording to the request to irrigate vast perimeters. All the water resources of the valley of Senegalis now partially under control, but the water management becomes complex to deal with sometimesconflict demands in term of uses. ■ Reduction of floods plains and wetlands The wetlands are often considered as fertile areas favourable for agriculture. Everywhere in theworld the development projects and in particular the construction of dams had an significant impacton the hydrosystems by reducing sometimes considerably the surface of the floodplains which areplaces 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 ecosystemsdepend on the nature of the catchment area and its vegetation. However the disappearance of theforests, 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 andwater turbidity, as well as a modification of the hydrological mode with shorter but more brutal runoffresulting from a more important streaming. The problem of the deforestation concerns Africa in general and the available information showsthat 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 hectarehave been reported. In the Lake Tanganyika drainage, deforestation is massive too. The erosion onthe slopes has resulted in significant contributions to the lake sediment and changes in wildlife insome coastal areas particularly vulnerable. If current trends continue, the figures are coming with anestimated worrying that at this rate, 70% of forests in West Africa, 95% of those from East Africa and30% 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 forthe planktonic and benthic photosynthesis. The suspension elements may seal the branchial systemof fish or cause irritation and muddy deposits deteriorate the quality of substrates in breeding areas. Subsistence fishfarming in Africa 7
    • 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.8 Subsistence fishfarming in Africa
    • Organisms with concentrated pollutants can enter to turn the trophic chain, and if the productis not degraded or removed, it will concentrate more and more with each trophic chain link, eg fromalgae to ichthyophagous birds. This phenomenon which is called biomagnification, shows that thepollution of environment by substances that are measured in very small quantities in water, can haveunexpected 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 thoughtthat fishing alone, when used with traditional gear, can not be held responsible for the disappearanceof fish species. Indeed, it is not easily conceivable that one can completely eliminate a populationby captures made as a blind man contrary with what can occur for hunting. However, a pressureassociated 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. Inthis species, the male is buccal incubator of a few large eggs. In the early 20th century, it referred tothe capture of specimens of 2 meters long, while since 1950 the species seemed to become veryrare. One of the clearest fishing effect is showned in the population demography, with the reductionin the mean size of species and the disappearance of large individuals. Indeed, if the fishery usuallystarts 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 ofspecies that can not reproduce collapsing dramatically. In the lake Malombe for example, the fishingof Oreochromis (O. karongae, O. squamipinnis) was done with gillnets. It has been observed in the1980s 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 speciesof large size of Cichlidae.II.4. INTRODUCTIONS While for centuries introductions of fish species have been promoted across the world to improvefish production, they have become in recent decades the subject of controversy among scientistsand managers of aquatic environments. Indeed, the introduction of new species can have significanteffects on indigenous fish populations. The introduction of new species in an ecosystem is sometimes the cause of the phenomena ofcompetition that may lead to the elimination of native species or introduced species. But there mayalso 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 fromintervention: 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 fromdifferent 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 theintroduction into Lake Victoria of the Nile Perch, Lates niloticus, a piscivorous fish being able to reachmore than 100 kg. To some scientists, this predator is the cause of the decline and likely extinctionof several species belonging to a rich endemic fauna of small Cichlidae which he fed on. ` Subsistence fishfarming in Africa 9
    • 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 52810 Subsistence fishfarming in Africa
    • 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 4Cyprinodontiformes 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 Subsistence fishfarming in Africa 11
    • 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.12 Subsistence fishfarming in Africa
    • 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 animalprotein contribution. Indeed, there exists a big risk of reduction of the captures of fishings whereasfishfarming 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. Subsistence fishfarming in Africa 13
    • Constraint Unsuitable Moderatly suitable Suitable Very suitable No data Figure 5. GIS assessment of potential areas for production fish farms in Africa.14 Subsistence fishfarming in Africa
    • Chapter 02TYPE OF FISHFARMING According to FAO (1997), aquaculture is defined as: « The culture of aquatic organisms including fish, molluscs, crustaceans and aquatic plants. Theterm culture implies some form of intervention in the rearing process to enhance production, suchas 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 organismsharvested by an individual or legal person who had owned throughout their breeding period areproducts of aquaculture. On the other hand, publicly aquatic organisms used as a common propertyresource, 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 unitof area and on the destination of the products. They are generally characterized by their degree ofintensification, itself definite according to the feeding practices; the external food supply representsindeed in general more than 50% of the total costs of production in the intensive systems. Howeverthe 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 theirdegree 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 thestructure of farming, without or with very few inputs. Generally, there are farming installed in basinsor 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 costsremain 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 ofrice and fishfarming belong to this extensive category, since the fish profits from the inputs broughtfor the culture of rice. 9 Semi-intensive fishfarming systems are based on the use of a fertilization or the use of acomplementary 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 aresatisfied by the inputs, with small or very few nutritional contributions resulting from the naturalproductivity from the basin or the water in which the fish is produce (lake, river). The food used inthese 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. Tointensify 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 highrenewal 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 differentiationbetween: 9 The models where the food is coming essentially (or only) from the ecosystem (case of theecosystem pond), systems called production fishfarming. The management of this type involves thefertilization or the complementary food, with the implementation of the polyculture. There is a stronginteraction 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 Subsistence fishfarming in Africa 15
    • 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,16 Subsistence fishfarming in Africa
    • 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, thefish industry, a long time regarded as a way of geographically concentrated production factors andto achieve economies of scale is generally comparable with the intensive concept and privatizationseems that he could not pass through it. It now appears that all such projects implemented so faron the African continent, have failed from their original purpose, ie to produce a fish at a lower costprice 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 foranimal proteins must be rather fast because of a lack for the populations. On the other hand, thistype 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 traditionin 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 developaquaculture dates back to the 1940s. The attempts to introduce aquaculture in Africa around 1950, were for diversification of sourcesof animal protein to promote food self-sufficiency of rural populations. The first tests performedwith tilapia in the station Kipopo established in 1949 (former Belgian Congo) have yielded promisingresults, the colonial government began outreach. In 1957 the station of Kokondekro near Bouaké inCôte d’Ivoire was created for the purpose of research and training. The first tests were carried onspecies now abandoned because of poor performance in intensive: Tilapia zillii, Tilapia rendalli andOreochromis 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 othertilapia. It is also from this period that one began to focus on the identification of other species of fishin 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 proteinat a lower cost and within a short time. So a fishfarm in extensive to semi-intensive, of production, requiring minimal technical to be Subsistence fishfarming in Africa 17
    • 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 secondary18 Subsistence fishfarming in Africa
    • Investment Super-intensive Deep-sea fishery Intensive Coastal fishery Semi-intensive Artisanal fishery Extensive Pond, wetlandAquaculture 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 theincrease in the number of age classes in an farm enclosure, competition leads rapidly to prevent agood growth of first stocked fish. The association of a predator to the farming of tilapia to control the undesirable reproduction of itis 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 Clariasis necessary to the total control of the reproduction of O. niloticus and that they exert a competitionwith respect to the food resources available in the pond. To control a population of 1200 tilapia inpond of 10 ares, a population of 260 Clarias of initial mean weight higher than 150 g is necessaryand the growth of the tilapia is lower than that of an identical farming in which Clarias is replaced bya strict predator (Hemichromis fasciatus). It was also noted that, in the presence of a predator, thetilapia tend to invest in the growth before reproducing, which could be related to the fact that theycan 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, evenwith 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 populationsof this invader by introducing a species which either will reduce the food of the intruder, or to feeditself directly on the intruder. 9 The production of natural foods is stimulated. The fish with digger behavior when theyare in the search of food can suspend particles and, thus, aerate the sediment, to oxidize the organic Subsistence fishfarming in Africa 19
    • 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.20 Subsistence fishfarming in Africa
    • Chapter 03BIOGEOGRAPHY AND FISH SPECIESI. GEOGRAPHY The fish faunas were established and have evolved according to the history of aquatic systemsthey 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 dependson 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 theshape of the basin. Communications can then be created between different basins. At various timescales, 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 phenomenaexplain 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 includesseveral catchment areas of different size. For example, the soudano-nilotic region includes severallarge basins like the Nile, Niger, Senegal. The political divison of the countries does not correspond little or not to the ichthyoregions. Acountry either is included completely in only one ichtyoregion, or with overlap on several. One willfind in Annex 04, the Table XLVI, p. 246 which indicates for each African country the ichthyoregionsof which its area forms part and in the Table XLIV, p. 240 of geographical information for each Africancountry. 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 areavailable, 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 mostimportant group is that of fresh water fish: 12,7 million tons, in comparison with 1,4 million tons foramphihalins 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 mealcontents limited; they can beings raised in polyculture, allowing an optimal valorization of the naturalproductivity of the ponds and water pools in which they are stored; they also correspond to growthmarkets 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: thetilapia (12 000 tons annual) and the catfishes (7 000 tons), and of the introduced species of whichthe carps (2 000 tons). Historically in fact the tilapia were the subject of the first work of aquaculturalexperimentation in Africa, mainly in DRC (ex-Zaire) and in Congo, in particular because of their easyreproduction 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 highpotential of the catfish Clarias gariepinus on which important research tasks were undertaken, havebeen put forward. Then in the years 1980, other species of fishfarming interest were identified, in Subsistence fishfarming in Africa 21
    • 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;22 Subsistence fishfarming in Africa
    • 9 They are appreciated by consumers. We know more than a hundred species of «tilapia» described. More than 20 species have beenrecorded in some countries (Annexe 04 p. 239). Some are endemic of lakes or very circumscribedzones. The maximum size observed is very variable and does not reach more than 5 cm until morethan 60 cm Total Length (TL). The species of Tilapiines are separate in various genera whose the 3principal ones are Oreochromis, Sarotherodon and Tilapia. This separation in genera is mainly relatedto 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 Sarotherodonare also mouthbreeders, but biparental, the two parents can incubate. The fish of the genus Tilapiaare 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 commonspecies. But many other species were also used: O. aureus, O. macrochir, O. mossambicus, Tilapiarendalli, 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 introducedinto natural environments to improve fishing, or which they are used as a basis for the fishfarmingproduction. Between 1984 and 1995, the contribution of the tilapia of fishfarming to the total production oftilapia 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 ofall Cichlidae. The Nile tilapia represented 72 % of the total production of tilapia; the annual growthrate of its production between 1984 and 1995 was of 19 %. In 1995, the principal producers of tilapiawere 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 arepredatory 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 veryinteresting for fishfarming because of their robustness and their rapid growth. Three species arecurrently well studied for domestication: Clarias gariepinus, Heterobranchus longifilis and Chrysich-thys nigrodigitatus. For example, Heterobranchus longifilis is present in most of the river basins ofintertropical Africa, and has biological characteristics which are particularly favorable to fishfarming:capacity to support hypoxic conditions because of air breathing apparatus, omnivorous diet, highfecundity 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 500described species, no species has actually been domesticated so far. Yet some species exceed50 cm TL like Labeobarbus capensis (99 cm TL), and Barbus altianalis (90 cm TL). There was someattempts to introduce Asian Cyprinidae as common carp (Cyprinus carpio), silver carp (Hypophthal-michthys molitrix), mottled carp (Hypophthalmichthys nobilis) and grass carp (Ctenopharyngodonidella). The common carp was first introduced to Madagascar and then scattered in a dozen othercountries including Kenya, Cameroon, Malawi, Ivory Coast and Nigeria. Tests were made with Labeovictorianus (41 cm TL) and Labeo coubie (42 cm TL). However, these are often species of runningwater and this can be a problem on their farm in pond where water is almost stagnant. Subsistence fishfarming in Africa 23
    • 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.» 24 Subsistence fishfarming in Africa
    • SummaryFISHFARMING: 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. TheConvention 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 unitof area and on the destination of the products. They are generally characterized by their degree ofintensification. Subsistence fishfarming in Africa 25
    • 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.» 26 Subsistence fishfarming in Africa
    • Part IIPRACTICAL 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 Subsistence fishfarming in Africa 27
    • 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 67Cover photo:Ö Villagers working on the pond, Liberia, ASUR, 2006 - © Yves Fermon28 Subsistence fishfarming in Africa
    • III.4. Layout of ponds 67 III.5. Size and depth of the ponds 68 III.6. Differences in levels 69IV. SUMMARY 71Chapter 07 - THE CONSTRUCTION OF POND 73I. THE DESIGN PLAN 73II. THE CLEANING OF THE SITE 75III. WATER SUPPLY: WATER INTAKE AND CHANNEL 77IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE 81V. THE PICKETING OF THE POND 82VI. THE CONSTRUCTION OF THE DIKES 83VII. THE DEVELOPMENT OF THE PLATE (BOTTOM) 89VIII. 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 105Ix. 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 109x. NECESSARY RESOURCES 109 x.1. Materials 109 x.2. Human Resources and necessary time 110xI. SUMMARY 112Chapter 08 - BIOLOGICAL APPROACH 113I. THE LIFE IN A POND 113 I.1. Primary producers 115 I.2. The invertebrates 116 I.3. The vertebrates 118 Subsistence fishfarming in Africa 29
    • 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 16430 Subsistence fishfarming in Africa
    • I.6. Summary 164II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION 165III. 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 171IV. 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 bementioned at the beginning of each chapter showing step processed. Subsistence fishfarming in Africa 31
    • 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.32 Subsistence fishfarming in Africa
    • Chapter 04THE 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 variousaspects of evaluation. This step has a duration of at least 3 months, which may increase dependingon 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 andinert nature, which is subject to complex interactions as a functional entity. Ecosystems vary greatlyin size, lifetime and operating. A temporary pond in a hole of a tree and an ocean basin are bothexamples 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 organicmatter starting from light energy, CO2 of the air and the mineral ions of the ground), to the variousconsumers (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 isalso 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 theconcept of factor ecological. Is known as ecological factor, any element of the external environmentwhich may affect the development of the living beings. For this reason, one distinguishes severaltypes of ecological factors: 9 Biotic factors, related to the biological components (biocénose), interactions of alive onalive, intraspecific (within the same species) and interspecific one (between two different species ormore); 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 absenceas by its excess. With respect to the ecological factors, each living being thus presents toleranceslimits 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 anecological factor. The ecological factors can thus act in various ways on the biocénose. They in particular willintervene 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 implyingsuch type of biocoenosis and conversely) of each ecosystem allow a zoning. Consequently for eachtype of ecosystem, it is possible to associate with this zoning: an operating process, goods andservices produced, known risks and threats… The human beings, as an integral part of the ecosystems, draw benefit from the “goods andservices” produces by the functioning of the ecosystems. The services provided by the ecosystemsinclude the services of deduction such as food and water; services of regulation like the regulation Subsistence fishfarming in Africa 33
    • 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 Drainig 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 61/4 - 91/4 months « Green water » Maintenance and  Resumption of a cycle 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 9. Setting of fish ponds: 1. Assessment.34 Subsistence fishfarming in Africa
    • 1. ASSESSMENTof the floods, the dryness, the disease and impoverishment of the soil; services of self-maintenancelike the formation of the grounds, the development of the nutritional cycle; finally culture sectionslike 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 biogeochemicalreactions affecting the biosphere and being characterized by permanent exchanges of matter andenergy 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 stronglyopen the ones to the others. There exist however more or less porous borders called ecotones. Theedge of a wood separating it from an agricultural field, a hedge cuts wind are good examples. Likeany 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 wetlandsconstitute a vast inter-connected network of exchange including the lakes, rivers, swamps and thecoastal regions. The living conditions and production of a human community depend always directly or indirectlyon the abundant services by the local ecosystems (water, food, wood, fiber, genetic material…). Asexample, 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…) couldgrow from 70 to 80 % over the 50 next years. With which ecosystems? This increasing demand willgenerate necessarily larger difficulties for the communities on the level of the access to the resourcesand 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 thesame territory: global environment (climate, biogeochemical major cycle) which evolves over a longperiod, local environment (production of biomass) over the medium period, human communities overthe short period. What to say on climate change, true producing of uncertainties affecting the globalenvironment. These moving temporalities and borders within the territories reinforce the prospectiveneed for the analyzes. Evapotranspiration Precipitation Evaporation Surface runoff Stream flow Source Infiltration Sea Ground water flow Figure 10. Water cycle. Subsistence fishfarming in Africa 35
    • 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.36 Subsistence fishfarming in Africa
    • 1. ASSESSMENTIII. PRINCIPLE The fast evaluation can be defined like: “A synoptic evaluation often undertaken in urgency, within the shortest possible time possible, inorder 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 ninefollowing 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 ofexisting knowledge and specialized data, including traditional knowledge and data, and methods ofstudy 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 practicalshortest times, even if the preparatory period and the work of planning which precede the studyare consumers of time. In some circumstances (when one takes account of seasonal factors, forexample) 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 beundertaken in urgency and the preparation time must remain minimal. 3. Inventory, evaluation and follow-up. When one conceives exercises of data acquisition thetype 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 forthe development of a suitable evaluation and a follow-up. The inventories of the wetlands, repeatedwith 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 vastspace 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 tohave 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, afast evaluation with large scales consists in applying a standardized method to a great number oflocalities 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 newevaluation 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 thedata 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 publishedand 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 goalof the evaluation can be reached with existing information or if it is necessary to lead a new studyin th field. A good cartography is essential to the good way of the evaluation and the futuredecisions 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 particularlyimportant 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 informationanalysis to provide a comprehensive assessment of the confidence limits of the final results of theevaluation. 9. Diffusion of the results. An important element of any fast evaluation is the fast, clear andopen diffusion of the results near a range of actors, decision makers and local communities. It isessential to present this information to each group in the form and with the level of precision whichis the best appropriate. Subsistence fishfarming in Africa 37
    • 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 state38 Subsistence fishfarming in Africa
    • 1. ASSESSMENTand the conditions of economic species, of species on which depend the means of existence andof 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 durabledestroying activities. The importance of the choice of fish as indicator is its importance also as ananimal protein contribution. It is a question of surveying which are the resources available in therivers close to the targeted villages. It is supposed that any fast evaluation must be done with the end objectives of conservationand rational use. The methods used are supposed to increase knowledge and understanding for thepurpose of establishing a reference, the evaluation of the changes in the ecosystems or their stateand the support to the durable use of the resource. In this context, there are five precise reasons toundertake 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 hierarchicalbasis 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). Togather relative data with the conservation of particular species. 3. To obtain information on the effects of the natural or induced disturbances (changes) by theman on a zone or a particular species. 4. To obtain indicating information of the general health of an ecosystem or of the statement of aparticular ecosystem of wetland. 5. To determine the possibility of using in a durable way the living resources in an ecosystem ofa particular wetland. Many fast evaluations do not allow to entirely evaluate the threats or the pressures on biologicaldiversity. 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 madeto 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 programof 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 biologicaldiversity generally are not related to “fast” approaches. Nature complexes and the variability of the ecosystems of the wetlands make that there doesnot exist universal evaluation fast method, applicable to all the range of the types of wetlands and tothe diversity of the goals for which the evaluations are undertaken. Moreover, which it is possible tomake, 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 ofwetland by sampling wide and as complete as possible of the biological elements and associatedcharacteristics. The lists of species and habitats will be probably the most important form of data, butof 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 thebiodiversity and other relevant biological information which is due to water quality, the hydrology andthe health of the ecosystem. The data on the geography, geology, the climate and the habitat arealso important. For the majority of the studies, it would be good to measure a diversity of variablesof water quality. Those can include the temperature, electric conductivity (EC, a measurement ofdissolved total salts), the pH (measurement of the acidity or alkalinity of water), chlorophyl A, totalphosphorus, 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 agreat diversity of methods, while taking into account the applicable legislation. To work with the localfishermen 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 generalistwill be limited by his knowledge concerning the aquatic organisms and the functioning of the eco-systems. Subsistence fishfarming in Africa 39
    • 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 so40 Subsistence fishfarming in Africa
    • 1. ASSESSMENTwide that it was almost impossible for them to have a balance diet. For example, part of the Bahayapeople which live close to Lake Victoria was accustomed to prohibiting the egg and milk, fish, meatconsumption 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 theseprohibitions were put in place just to avoid an excessive level of predation in an area rich in fish andthus 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 thelower 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 thevisits 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, itwill then be a question of making sure of its source and its availability. For example, in Liberia, thevillages 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 ofthe diversity of the food products available. It will be necessary, however, to separate well the cattlewhich 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 pointswhere people will be provided (well, pump, river…) and assess their condition.V.3. THE RELATIONS MAN-MAN¾ 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 thetime, they are the men who go to fishing but the women deal with collecting fish, to transform it andsell it. At others, fishing is practiced by the women and becomes a corporate measure. In Liberia, thewomen with the children go away the afternoon to the river to capture with large scoops nets. Theytake 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 andwhich are the key and notable people. The groupings, their operation…, are a key of the success ofprograms 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 whichare important to know insofar as fishfarms will be established on some privileged zones. Water andits 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 satisfiedto 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 fishfarmingtradition and where ancestral know-how, although empirical, plays a crucial role. The many attemptsat transfer of these fishfarming models towards countries where there was no fishfarming traditionfailed. Subsistence fishfarming in Africa 41
    • 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.42 Subsistence fishfarming in Africa
    • Chapter 05VILLAGES AND SITES SELECTIONS If the initial assessmenst justify an intervention, the first stage will be thus to choose villages ofestablishment, by making sure that those have adequate sites in the vicinity (Figure 12, p. 44). Thischoice can be already more or less defined according to the preliminary assessment and of the visitsof 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 villagesand 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 populationssaid vulnerable. 9 Proposed projects are usually fairly short. The number of villages targeted should thereforebe chosen depending on the duration and logistics that will be available. However, it is unrealisticto propose a fishfarming project for less than 12 months. Indeed, the establishment of a pond of200 m2 overall request 20 days to 20 people. If it is the beneficiaries who lead the workforce, it musttake into account the fact that for most, their main activity is agriculture and they thus will devote onlya time restricted to the construction of the pond. 9 One will not be able to also choose villages too distant because of times from transportand inherent logistics. Often, the technicians are used as catalysts for the beneficiaries and theirpresence 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 implementedduring 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 willbe the certainty which the villagers are motivated whereas in fact, their interest is located especiallyto obtain something on behalf of international NGOs operating in the zone. It will often be a totalfiasco as the village investment in building ponds. It will thus be a question of seeing well whether theproteins fish are essential and missing in the zone. This means to see if the fish proteins are essentialand missing in the area. This will be particularly important if the request comes from the villagers, thiswill 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 morein detail in the following paragraph (paragraphe II, p. 45). It is essential that the village has enoughrunning 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 theelements allowing a good appropriation of the project by the beneficiaries. It is necessary that thebeneficiaries 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 establishthis 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 interfamiliesproblems for the management and distribution of harvests. If perennial associations would exist, it Subsistence fishfarming in Africa 43
    • 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 Drainig 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 12. Setting of fish pond: 2. Selections.44 Subsistence fishfarming in Africa
    • 2. SELECTIONSwill 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. thepresence 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 theprincipal requirements are respected. In this chapter and the following, the major part of the drawings and texts are classic and oftencomes 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 caninclude: 9 Perennial systems which know flows of surface all the year and are not drained during thedrynesses. 9 Seasonal systems which know expected flows during the annual rainy season, but whichcan 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 byrainwater as by subterranean water. Sometimes, flows of surface can only occur in some parts andbecome underground in the others. 9 Transitory systems (with short life) which know briefly and seldom flows and which, betweentwo, return under dry conditions. Their flow generally comes from precipitations. A running water present continuously throughout the year (dry and rainy season) facilitates themanagement 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 havea good oxygenation and mitigating water loss. The amount of water needed will depend on the size of ponds, soil and climate prevailing in thelocality. ■ 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. Subsistence fishfarming in Africa 45
    • 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.46 Subsistence fishfarming in Africa
    • 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 afishfarm of one hectare, it takes 2 to 5 liters water per second. This water flow is thus to controlduring the dry season. On the other hand, we must also check if there is no risk of flooding. People living locally arebetter informed. They know if there are significant flooding and water flows all year. You can alsocheck the marks of water levels on the banks and bridges. A pond should not be built where thereare 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 flowlower 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 channelsall 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 inregular 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. Subsistence fishfarming in Africa 47
    • II.1.2. WATER QUALITY One can have more water in quantity than necessary, but if its physico- chemical 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.48 Subsistence fishfarming in Africa
    • 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 arrangedby using a pole, a piece of paper of white polyethylene and a meter. The piece of white paper is fixedat the lower end of the pole that is vertically immersed in water. One measures the depth where thewhite paper disappears from the sight. One continues to immerse it. Then, one goes up and oneagain notes the depth to which one sees reappearing paper. The depth is evaluated by the averageof 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 saltconcentration 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 factits 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 ofperforming the test, one washes the hands with soap by using a sample of water to be tested. It willbe 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 ofwater dropped much. The pH represents the concentration of water into hydrogen ions (H+), or more simply gives ameasurement of acidity or alkalinity of water. Thus, water is neutral with pH = 7, acid if the pH is Subsistence fishfarming in Africa 49
    • 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.50 Subsistence fishfarming in Africa
    • 2. SELECTIONS If the ball is falling apart,  the soil contains too much  sandA - 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). Subsistence fishfarming in Africa 51
    • 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 is52 Subsistence fishfarming in Africa
    • 2. SELECTIONSthus returned seals by contribution of a surface layer of 30 cm thickness clay. A rock ground is oftendifficult to work without mechanics, and is sometimes traversed by cracks which it is necessary toseal by clay. The chemical characteristics of the soil depends on the colloid concentration, the degree ofsaturation in exchangeable bases, the capacity of exchange cation or anion, the capacity to makeavailable various biogenic salts… The soil must thus contain an amount of exchangeable mineralssalts. This is possible if the soil contains a certain proportion of organic matters. The natural wealthof 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 inthis last case to invest very heavily in quicklime in order to raise the pH of the water for its fishfarmuse. 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 ofsavanna is richer and less acids than water emerging from the forest, but the risks of pollution bythe sediments are greater (gullying, erosion). The richer the crossed grounds are in rock salt and themore water have then a strong natural productivity, because the proliferation of the phytoplanktonand 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). Subsistence fishfarming in Africa 53
    • 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.54 Subsistence fishfarming in Africa
    • 2. SELECTIONSning 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 andFigure 30, p. 57). It is expressed as a percentage. A stake in top and a stake in bottom of the slope areplaced. One horizontally tightens a rope between the two stakes using a plumb level. In absence oflevel, a bottle filled with water can make the level. This device is particularly practical, since it makesit possible to proceed quickly, even on an unequal grassy ground, and with a sufficient precisionA. Low slope (1 to 3%)SuitableB. No slopeHow to empty the pond ?Unsuitable Break of the dike High pressureC. Strong slopeUnsuitable 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. Subsistence fishfarming in Africa 55
    • (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].56 Subsistence fishfarming in Africa
    • 2. SELECTIONSground on profitable way by considering by anticipation the various components of an integratedfishfarming with the other production of the rural world (grass for bovines, fruits as food or fertilizersin the ponds, zones really water full for cultures like rice,). The cleansing and the drainage of water inthe 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 inthe 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. Subsistence fishfarming in Africa 57
    • 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.58 Subsistence fishfarming in Africa
    • Chapter 06CHARACTERISTICS OF THE PONDS Once the choice of the villages then sites of installation of the ponds made, it now acts to set upthe ponds (Figure 32, p. 60). The fish production is based on the use of earth ponds which contain freshwater, renews it, andallows 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 goodmanagement 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 adaptedto 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. Sothey 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 tothe pond. • The draining channel or evacuation which is the work allowing the drainage towards theemissary. 9 The devices of regulation, which control the level of water or its flow through the pond, orboth: • The water inlet which is the device designed to regulate the water flow towards the pondand which protects water from the floods. • The water outlet preferably a monk which allows the control of the level of the water andevacuation of the pond. 9 The outfall or overflow which allows the evacuation of the water excess of the pond andensures 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 ofdraining them, materials and processes of construction and, finally, the methods of fishfarm. Thecharacteristics 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. Subsistence fishfarming in Africa 59
    • 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 Drainig 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 61/4 - 91/4 months « Green water » Maintenance and  Resumption of a cycle 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 32. Setting of fish pond: 3. Ponds.60 Subsistence fishfarming in Africa
    • 3. PONDS Regarding the use of the pond, it is certain that the same pond can be used for various usesaccording 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 supplywaste materials to the pond as feed or fertilizer; In this case, only the ponds usable for the subsistence fishfarming and which are the most viableponds, will be considered. The principal characteristic will be that they are entirely drainable withrunning water available all the year. We will not take into account, ponds collinaires supplied withstreaming 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. Subsistence fishfarming in Africa 61
    • 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.62 Subsistence fishfarming in Africa
    • 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, nospillway, complete drainage, easier pond management), but construction costs can greatly increase if the diversion of a large waterflow has to be planned.** Relative advantages will vary according to the arrangement of the ponds, either in series (pond management is more difficult) orin parallel (both water supply and drainage are independent, which simplifies management).III. CHARACTERISTICSIII.1. GENERAL CRITERIA According to the needs, it will be possible to build a series of ponds with a management inshifted 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 accordingto 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 pondsand to better keep water (Figure 37, p. 66). While seeking to position the downstream-dikes across theflow 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 theintake and draining and the availabilities of water. A provision of the ponds to the current does notmaximize suitable surface (B): Surface in green is not used. This flow is carried out parallel to thewater course. On the other hand, in the diagram (C), water is blocked in its flow perpendicular tothe water course since all the ponds are on the same level. More water will then be stored in thebasement above the plans of ponds. It will be available to fill the ponds again or to limit the lossesduring the dry season. Subsistence fishfarming in Africa 63
    • Stream Spillway and overflow Outlet Inlet to pond Dam Larger stream Water intake Outlet Diversion channel Dam Figure 35. Examples of barrage ponds.64 Subsistence fishfarming in Africa
    • 3. PONDS OutletLarger stream Pond Pond Pond Diversion channel Pond InletLarger stream Diversion channel Outlet Pond Pond Pond Pond Pond Inlet Pond Figure 36. Examples of diversion ponds. Subsistence fishfarming in Africa 65
    • 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).66 Subsistence fishfarming in Africa
    • 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 toeach 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. Subsistence fishfarming in Africa 67
    • 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 markets68 Subsistence fishfarming in Africa
    • 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 growthof the watery plants. Deeper ponds are of a construction much more expensive because the volumeof 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 waterto 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 pondseasily 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). Subsistence fishfarming in Africa 69
    • 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.70 Subsistence fishfarming in Africa
    • 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. Subsistence fishfarming in Africa 71
    • 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 control72 Subsistence fishfarming in Africa
    • Chapter 07THE CONSTRUCTION OF PONDS Once the site is chosen, it acts to carry out the construction of the ponds and the associatedstructures (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 onesfor 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 orless 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 testI. THE DESIGN PLAN With this stage, one studies one or more possible localizations of the ponds. A first selectionis taken minimizing work compared to clear surface. The design is progressive: The assumptionsformulated on the filling and the diversion of water are progressively evaluated as to the completionof 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 bedeveloped. 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 groundusing a level stake. A letter corresponding to the same letter on the future topographic chart iswritten on the top of the stake. Spacing between the points will depend on the topography of theground. If the ground is very undulated, the points will be very closed. The first point can be take onthe 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 thesetwo points. Subsistence fishfarming in Africa 73
    • 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 Drainig 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 61/4 - 91/4 months « Green water » Maintenance and  Resumption of a cycle 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 47. Setting of fish pond: 3. Ponds.74 Subsistence fishfarming in Africa
    • 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 sothat they are most functional possible, particularly from the point of view of the drainage and watersanitation. The arrangement of the various structures on the topographic map will have to be done by takinginto 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 cleanthis 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 orposts. 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 (Figure49, 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 theaccess roads and the installations of water supply and drainage. Subsistence fishfarming in Africa 75
    • 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.76 Subsistence fishfarming in Africa
    • 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 waterfrom the main channel to the pond. The principal water intake are used to regulate overall and to derive the water supply from a pondor a group of ponds. They have primarily the role to ensure a regular water supply, which may beregulated 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 bemade whatever the level of water in the bottom of the valley. This condition is very important andmust be strictly respected. In too often cases where it is not, the ponds are just simple diverticulaof rivers whose flood demolish the dike and where the fish enter and leave easily. One makes somesurveys 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 issufficient 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 toregulate the water supply of the ponds; such a device is generally connected to the transport ofwater structure;Ö A structure of protection of the entry, for example stilts to prevent any deterioration of the waterintake due to the debris. One will use an open or free level water intake in which the levels of supply are not controlled andwhere the water catch functions under all the conditions of flow. This system is simple and relativelycheap, but it generally requires a reliable water supply which does not vary too much. Subsistence fishfarming in Africa 77
    • 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 -78 Subsistence fishfarming in Africa
    • 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 waterpenetrates there, is to be avoided because it systematically results in giving a slope too much strongto 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 and1.00 m/s in stones. If one cannot follow the level line for an unspecified reason and that one must reduce the level ofthe 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. Subsistence fishfarming in Africa 79
    • 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].80 Subsistence fishfarming in Africa
    • 3. PONDSas reference mark for the depth and to reject the excavated materials downwards in order to avoida 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 usedto check as the constant width of the ceiling and the regular slope of the banks was respectedstrictly, 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 onewill be built out of perfectly compacted ground and the peak, of a sufficient width, will have to reacheverywhere 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 therisks from erosion. On the other hand, the installation of the overflows, the settling basins and theditches 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) bysmall sections starting from the river until the sufficient depth so that water runs there, systematicallyleads 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 55below). The ponds must be able to be emptied throughout the year without remaining there anywater pool. For that, it is necessary that the bottom of the channel of draining is much lower than thebottom 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, thewater level in the valley is higher than the bottom of the pond, one will not be able to use the bed ofthe valley like channel of draining. If, on the contrary, this water level is permanently lower than thebottom of the pond, one will be able to use the bed of the valley like channel of draining. It is alsopreferable to set up a channel of drainage around the zone of the ponds. Now, the following stagewill be to fix the site of the ponds on the area between the supply channel and the position of thechannel 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. Subsistence fishfarming in Africa 81
    • 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.82 Subsistence fishfarming in Africa
    • 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 thesite of the dikes of all the debris which could be there: roots, plants, stones… One also removes thesurface layer of the ground, (i.e. the layer of cultivated ground), where the dam must be built, to avoidthe water escapes through the base of the dike when the pond is underwater. Most of the time, oneforgets 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 theirwalls (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). Subsistence fishfarming in Africa 83
    • 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.84 Subsistence fishfarming in Africa
    • 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). Subsistence fishfarming in Africa 85
    • 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.86 Subsistence fishfarming in Africa
    • 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 insomewhat 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 isusually expressed as a ratio defining the change in horizontal distance (z in m) per metre of verticaldistance as, for example, 2:1 or 1.5:1. In a dike with side slope 2:1, for each 1 m of height, the basewidth 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 becomesstronger; 9 As the slope ratio increases, the volume of earthwork increases, and the overall land arearequired 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 XVIabove), depending on local conditions for ponds of 100 to 600 m2. The slope of the dry side can bemade 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 theponds (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 sandyground (A). The good argillaceous soil is transported and compacted wet, by a compactor or whilerolling 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 largestones) 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 accordingto this technique called “in staircase”. One uses a compactor, a barrel, or a roller for compactingeach 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 rammedand compacted vigorously (C). After having assembled the dike, step by step, until the height ofdesired water (0.6 to 1.2 m) according to the type of pond (laying, stocking with fish, parent) andwithout forgetting the height of the freeboard of 0.25 m, it is enough to flatten the edges of the stepswith a wooden handle. In the very argillaceous soils, the soil is more difficult to work and some prefer to build the dikeswith blocks of ground which they cut in the ground. The sandy grounds are easier to work and arecrumbled in the hands: they are very permeable and are less appropriate for fishfarm (D). To builddikes on clay soils, one proceeds in the same way, (method of the staircase) but one moves theground by cut mound, removed the vegetable top layer and the large vegetable debris (E). With alittle 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 Subsistence fishfarming in Africa 87
    • 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.88 Subsistence fishfarming in Africa
    • 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 intop 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 thatof 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 waterinlet to the outlet, to ensure an easy and complete dry setting of the pond. One must always makesure 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 ofdrainage towards the emptying device is very useful. It is preferable to ensure a complete dry settingby a network of not very deep ditches of draining and having a slope of 0,2 %, rather than to seek tocreate 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 drainsconverging of the edges towards the zone of draining. The drains are small channels built to facilitate I = Inlet I I O = OutletI OA 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). Subsistence fishfarming in Africa 89
    • 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.90 Subsistence fishfarming in Africa
    • 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 requiredand the inside diameter of the pipe (Figure 76opposite). Usually, pipe inlets extend for about60 to 100 cm beyond the edge of the water sur-face of the pond when it is full, and they shouldbe at least 10 cm above the final water level.One will mainly use PVC pipe or plastic, whichare resistant and do not deteriorate easily. In thecases where they are not available, bamboo can Figure 76. Pipe inlet.be used. Bamboo pipesmake cheap and good inletswhenever locally available (Figure 77 opposite).They can be used in several ways for filling smallponds, for example: 9 Without modification, the water flow Oblique being regulated upstream; Flow cut 9 With the inclusion of a mobile plate forflow regulation; Metal plate to  open and  9 With modification for improving water close pipequality. Flow VIII.1.2. GUTER INLETS Gutter inlets usually extend for about 1 mover 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 endlengthwise in half and cleaning out the partitionwalls. 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 caneasily be added; 9 Metal: by bending lengthwise a galvanized iron sheet into a semi-circular gutter. The flowshould be regulated upstream. Subsistence fishfarming in Africa 91
    • 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.92 Subsistence fishfarming in Africa
    • 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 organicmatters in suspension, such as vegetable debris. 9 To limit the wild fish introduction, which can take food, transmit infections and diseases andreduce the production of the ponds. The carnivorous species can destroy the fish stock, in particularsmaller ones. It is possible to make various types of more or less effective structures and more or less heavyto implement. Initially, one can put a rather coarse stopping like a grid, on the level of the generalwater supply channel or the pond to prevent the large debris to pass into the ponds. For the aquaticanimals, one will use finer structures. Often, simple net, sometimes mosquito net, were used onthe 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 SandWire netting DebrisConcrete Water supply  channel Water Pond Wild fishes Dikes Figure 81. Diagram of an example of sand filter. Subsistence fishfarming in Africa 93
    • 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.94 Subsistence fishfarming in Africa
    • 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 throughthe 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 of10 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 pondWater level Drainage of the waterProtection of the pipe Downstream dike Downstream dike Drain pipe Drain pipe Figure 82. Turn-down pipe inside pond outlet. Subsistence fishfarming in Africa 95
    • 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.96 Subsistence fishfarming in Africa
    • 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 tomake it so that it is leak-proof. If not done properly, the mortar surfacing will have to be redonefrequently, increasing maintenance costs. Generally, wooden and concrete monks are cheaper andeasier 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; thejunction 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 andsize as much as possible; and, for concrete monks, one need to prepare strong forms and re-usethem if possible.Ö One have to provide a separate overflow wherever there is danger of uncontrolled entry of floodwater into the pond. Top of the  Top of the  dike dike Monk Monk Outlet Outlet Dike DikeA B Figure 85. Position of the monk according the downstream dike. A: Integrated in the dike; B: Inside the pond. Subsistence fishfarming in Africa 97
    • ■ 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.98 Subsistence fishfarming in Africa
    • 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 flagstonesof 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 anchoringon each side of the column. It is necessary first of all to insert these two posts until a sufficient depthin 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 drainin wood (Figure 87 above). It is enough for this purpose assembling by nails or screws four boardsassembled out of rectangular box. One carefully fixes the drain thus carried out on a well compactedsoil 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 builtusing single- thickness brick and mortar. Although taller and wider monks can be built, they requirea double-width base and good bracing for stability and strength, and so become too heavy andexpensive 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 ofa coating. This technique revealed three major problems: 1. The breeze blocks are hollow and rough-casting is exhausted quickly. Escapes, not easilyreparable, appear on the growing old monks. 2. The monk is often unnecessarily tall within sight of the flow which the pipe can evacuate (whatrequires 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 orthe 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 qualityof 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 themould. This technique presented a difficulty at the time of its implementation. The construction of themould on the spot proved to be delicate, the sometimes hazardous dismantling and the problematicrecovery of the boards. What increased much the cost of construction. The monks were generally ofdifferent 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 astandard dimensioning. However, the first moulds were rather heavy to transport. When the fishfar- Subsistence fishfarming in Africa 99
    • 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).100 Subsistence fishfarming in Africa
    • 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 mnfrom height, 0.7 m of width of the back, 0.54 m for the wings and 0.15 thickness. The mixture of theconcrete 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 sectionof the monk increases according to the diameter of the drain (Table XVIII above, Table XIX and Figure89 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 to10 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 beall the more large as the capacity of flow is high, without however exceeding a maximum value from35 to 40 cm To facilitate the operation of the small boards, it is preferable to limit the interior width of a monkto 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. Subsistence fishfarming in Africa 101
    • 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 highest102 Subsistence fishfarming in Africa
    • 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 fishraised 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, itcrosses 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 asplane 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 upconcrete tubes. If one wants to obtain the best results, the drain must have a good foundation whoseconstruction must be done at the same time as that of the column of the monk (Figure 91 and PhotoL 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 toadd 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 verypractical;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; Subsistence fishfarming in Africa 103
    • 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.104 Subsistence fishfarming in Africa
    • 3. PONDSVIII.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 quantitiesin certain waters with a high turbidity. This is achieved by reducing the water velocity sufficiently toallow 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 (Figure94, 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 standardlength to be shorter. As long as the critical velocities are not exceeded, the basin can be shapedto fit local space and to minimize construction costs. As a general guide, ratios of length: width aretypically between 2:1 and 5:1. The bottom of the settling basin is built lower than the bottom of the water feeder canal, toconcentrate 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 longerzig-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. Subsistence fishfarming in Africa 105
    • 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.106 Subsistence fishfarming in Africa
    • 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 risksof erosion of the catchment area. The erosion of the ground has negative effects on water qualityand on the fishfarming installation itself. When water runs out on a slope, it involves with it particlescoming 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 theslopes to prevent that turbide water does not go in the ponds (Figure 97 below). This practice, calledconservation 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 particlesof ground and to increase the permeability of the sub-bases. The organic matters which it brings inthe ground, like the humus, increase resistance to erosion and slow down the streaming. It can alsocontribute to the deposit of the particles of ground. By arranging the natural vegetation on the slope grounds, it is possible to guarantee that theground acquires a greater resistance to erosion. In the zones covered with forests, it is necessary tocompletely maintain the cover of the ground as possible by managing the exploitation of the treesand by protecting the forest against the excessive pasture and fires. The forests having a goodlow vegetation, well disseminated radicular systems and a good cover by the leaves offer the bestconditions. In the zones of savanna, one will control the use of fire for the regeneration of the grazinggrounds and will give the preference to early fires to guarantee sufficient new growths before thebeginning of the rains. It will be necessary to avoid the excessive pasture, in particular by the sheepand 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 tocollect and divert water turbides or, if necessary, to improve water quality of food by using a settingbasin (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. Subsistence fishfarming in Africa 107
    • 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). C108 Subsistence fishfarming in Africa
    • 3. PONDSIx.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 inletand 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 RESOURCESx.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 earthworksand works, as indicated hereafter: 1. Descriptions of the earthworks: (i) Preparing the ground of the site, in particular clearing and uprooting complete, handlingand placement of the cleared vegetation; (ii) Removal of the layer of topsoil, with indication of its surface, its thickness and places ofstorage; (iii) Construction of the dikes, with indication of the source and the quality of the ground as wellas its characteristics; (iv) Compaction of the dikes, with mention of the maximum thickness of the layers, the moistureof 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 beused 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; Subsistence fishfarming in Africa 109
    • (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 – 2.0110 Subsistence fishfarming in Africa
    • 3. PONDS The standards of work relating to the earthworks carried out with the hand will depend mainlyon the nature of the ground. The harder it is to work and the less high the outputs are. The presenceof water in excess results also in to reduce the outputs, in particular in the presence of clays heavyand sticking One will see in Table XX, p. 110 examples of duration for each section of work. Times strongly varyand 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, anoffice 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 toTable XXI, p. 110. They are the average outputs to the excavation and the throw at a distance from 1 mwhich one can discount of medium worker who carry out earthworks during eight hours per day: theminimal values correspond to the use of the hoe and the maximum values with the use of the pickaxeand the shovel under similar conditions. These outputs must be slightly reduced when the distancefrom throw increases. For work of excavation and shaping of the channels, the output of a qualifieddigger varies from 0.8 to 1.2 m3 day. One can estimate the duration of the work overall, but for eachcase, 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 constructionwill be weakest. The most favourable moment is thus the dry season, especially at the end of theseason for the earthwork. At this time, the bearing pressure of the ground is better and the swampsare not saturated of water. For the programming of work, one thus designs a calendar in which theprogramming 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 Subsistence fishfarming in Africa 111
    • 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 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 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 upstream112 Subsistence fishfarming in Africa
    • Chapter 08BIOLOGICAL 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 developmentof 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 andalgae, 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 matterinto 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 photosyntheticplants. Thereafter, it can be assimilated and transformed by the animals. The animal organismsconsume 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 thisprocess to mineral matter. It is estimated that one needs 1 kg of phytoplankton to obtain 10 g of fishlike tilapia (Figure 101, p. 115). The population of each trophic level must indeed be definitely higherthan 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. Subsistence fishfarming in Africa 113
    • 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 100. Setting of fish pond: 4. Fishfarming.114 Subsistence fishfarming in Africa
    • 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 iscomposed by a wide variety of aquatic algae which are free in water (without substrate). Thesealgae are made up either of a cell (unicellular) or several cells (pluricellular) (Figure 102 below). Theirpresence in very great number gives blue green to maroon green color to the water of the pond. Thephytoplankton has two very important functions in a fish pond. Firstly, it is an oxygen producer andsecondly, 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 shortand 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. Subsistence fishfarming in Africa 115
    • 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.116 Subsistence fishfarming in Africa
    • 4. FISH FARMINGsion in water. Some rotifers are parasites of crustaceans, molluscs and annelids. They composemost of the zooplankton of freshwater and constitute a source of important food in the fresh waterecosystems (Figure 104, p. 116). I.2.2. THE CRUSTACEANS Part of the organismscomposing the zooplan- Adult Larvaekton are small crusta-ceans which are mainlydivided in two classes, inascending sizes. It dis-tinguishes the cladocersand the copepods (Figure105, p. 116 ). The zooplan-kton form an excellent Dytiscusfood for many fish spe-cies especially during thelarval stage. However, the 4 to 8 mmlargest copepods are pre-dators of eggs, larvae andeven of fry. It is importantto know the dynamismof development of the Dragonflygroups composing thezooplankton. One will beable to also find in water 10 to 20 mmsome crustaceans whichare parasites of fish andpredators. Moreover, thepresence of crabs andshrimps 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 onlyafter one week that the population of the cladocers reaches itsoptimum and the same, after ten days for the population of thecopepods. I.2.3. THE INSECTS A large part of the aquatic invertebrates are insects (Figure106 above). Most of the time they are larvae such as mosquitos,dragonflies, flies, ephemers, trichopters… which have a phase oflarval aquatic life and, after emergence, will spawn in water. Bythis 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 waterbeetles (Dytiscidae) and the water scorpions (Nepidae). They arealso, 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 aparasitic disease, schistosomiasis. Figure 107. Molluscs. Subsistence fishfarming in Africa 117
    • 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.118 Subsistence fishfarming in Africa
    • 4. FISH FARMINGMost 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 CO2organic matters. II.1.1. ANIMAL MANURE CO They constitute an additional source of car- 2bonic gas (CO2), which is very important for the Zooplanktoneffective use of the nutritive elements presentin water. They increase the abundance of bac-teria in water, which accelerate the decomposi- Bacteriation of the organic matters, and are also usedas food for the zooplankton, which in its turnalso increases in abundance. They have bene-ficial effects not only on the structure of the soilof the bottom of the pond but also on benthicfauna like the larvae of chironomids. However,the animal manures have some disadvantages,most of the time related on their low content of Benthic faunaprimary 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 conditionsof 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 arepoorer in nutritive elements, in particular when the animals eat only grass. Their fiber contents arerelatively 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 amanure more concentrated than those which are in freedom. One can design the shelters of animalsin 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 tobe exploitable in the large ponds. 9 Manure of pig which is usable only by non Muslims. Association pigsty and fishfarming arevery interesting by the outputs and the facilities which it gets. One will let dry this manure during 2weeks before using it. 9 The manure of cow and other ruminants which is to be used with many precautions becausethey are too rich in cellulose and risk to cause an important fermentation which will make fall brutallythe 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 overthe ground. 9 Liquid manure is a liquid oozing of a heap of manures after a rain or a watering is only foundin the breedings where one collects the urines and the manure. It is excellent for the production ofzooplankton 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 Subsistence fishfarming in Africa 119
    • 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/week120 Subsistence fishfarming in Africa
    • 4. FISH FARMINGÖ The vegetation which was cut in the pond itself, the channels or other water places. In someareas, harmful floating plants like the water hyacinth (Eichornia crassipes), the water ferns (Salviniasp.) 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 ponddrained before the filling, or be used regularly to fertilize water. The vegetation such as graminaceouscrossed, 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 inTable XXVI (below). They should be used regularly, while avoiding overloading the pond for severalweeks. 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 inprimary 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 compostare composed of relatively tender plants like the leaves, grasses and aquatic plants, which one mixeswith 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 someagricultural systems, one uses the two types of composting, for example the aerobic preparation inthe parts external of material and the anaerobic preparation in the interior zone where there is littleoxygen. 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 isthen important to ensure that there is always air in the heap of compost to maintain a fast and totaldecomposition 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 vegetablematters, for example of the rachis of leaves of banana tree, straw or stems of sugar cane, on a heightof 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 Subsistence fishfarming in Africa 121
    • 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 level122 Subsistence fishfarming in Africa
    • 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 materialand 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. Subsistence fishfarming in Africa 123
    • 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.124 Subsistence fishfarming in Africa
    • 4. FISH FARMING In heaps In rowsA 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 1mA 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. Subsistence fishfarming in Africa 125
    • 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 compost126 Subsistence fishfarming in Africa
    • Chapter 09THE 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 inAfrica according to the basins and countries. Consider again the sequence of operations, activitieswill 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 assessmentpreviously 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 willtry 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, andin order to limit the costs, one will avoid most of the time providing oneself in fingerlings from local producersI. CATCH METHODS On a fish farm, live fish have to be handled on many occasions, for example during routinemonitoring of their growth and health, transfer from one pond to another and final harvesting. Thishandling 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 beneficiariescan 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. Subsistence fishfarming in Africa 127
    • 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 116. Setting of fish pond: 4. Fishfarming and 5. End of cycle.128 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLEI.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 floatsmeshs of approximately 1 cm is used, the fishcatch will have at least 5 cm length. To collectjuveniles, one will use seines made with mos- Mounting twinequito net. A seine net is the most common type of netused on fish farms to harvest fish. It is a long netwith ropes at each end and is pulled along thepond to collect the fish and then drawn into acircle to trap them and, most often, bring back Netting Depth of netto the shore. A seine net consists of one or more piecesof netting material mounted (Figure 117 oppo-site): 9 At the top on a head rope equippedwith floats; Mounting twine 9 At the bottom on a foot rope equippedwith sinkers (or leads). Foot rope with  These ropes are normally extended beyond sinkersthe netting to form pulling ropes. There are several kinds of seine. The twofollowing designs are most commonly used. Figure 117. Diagram of a seine.Ö The seine is made similarly over all itslength. 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 eithertwisted 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 materialwhich floats Sinkers are usually made either from baked earth or lead. In this last case, they are available asthin lead sheets or in the form of olives of various individual weights. Lead recovered can be used. Atotal weight of sinkers equal to 1 to 1.5 times the total floatability of the floats is need. Small stonescan 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 3intervals. 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 thenet vertical with the wooden poles (Figure 119, Figure 120 and Figure 121, p. 131 and Photo O, p. 132). fno poles are used, take care to keep the bottom rope slightly ahead of the top rope. With a muddypond bottom or with a larger and heavier seine, additional strength may be needed. In this case, oneperson pulls at each end pole of the net while others assist by pulling at the extended end ropes. It isuseful to have an additional person standing near the middle of the seine while it is being handled tohelp whenever necessary, for example when it gets stuck on some underwater obstacle. Subsistence fishfarming in Africa 129
    • 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.130 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLE 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 pocketB C D Transfer the fish to  a container using  a hand netE E Figure 121. Manipulation of a seine. Subsistence fishfarming in Africa 131
    • 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].132 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLE 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 thinnerand usually made of synthetic monofilament such as polyamide monofilament with a diameter from0.12 to 0.25 mm, depending on the opening of the mesh. Mesh size is determined by the size of fishto be harvested. Fish should be able to pass through the extended mesh just beyond their gill covers but notfurther. (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 highlyselective. The mesh size is calculated by measuring the body perimeter, or girth, of a few fish of thesize you wish to harvest. Your gill net should have a stretched mesh size about a quarter smaller thanthe fish girth. Gill nets of stretched mesh size less of 4 cm or de 2 inches have to be avoid, for notcatching 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 thecast 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 joininto a single pulling rope. As it is not very easy to make, you can buy your cast net from a specializedstore. Skill is required in the handling of a cast net (Figure 123 and Photo Q, p. 134). It should be thrownwell opened and horizontally on to the water surface. It sinks rapidly to the bottom, and is closed bypulling 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. Subsistence fishfarming in Africa 133
    • 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);134 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLE Round Square or rectangular Half-round Handle Frame Bag Photo R. Dip net (Guinea) [© Y. Fermon]. 9 A handle, made from metal or wood and0.20 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 inmind. Handle live fish using dip nets with relatively shallow bags. Their depth should not exceed 25to 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 thewild. It might be the case to catch broods-tock or associated species as catfish.Certain kinds may be useful for simple andregular harvest of food fish without distur-bing the rest of the pond stock. These traps are usually made withwood, plastic pipe, bamboo or wireframes, with netting, bamboo slats or wiremesh surfaces. Opening: 25 to 30 cm There are two main types (Figure 125 Length: 80 to 100 cmopposite and Photo S, p. 136): 9 Pot traps, which are usually bai-ted and have a funnel-shaped entrancethrough which fish can enter but have dif-ficulty escaping from; and 9 Bag or chamber traps, whichusually have a guide net that leads the fishinto a chamber and have a V-shaped en-trance that keeps the fish from escaping. Figure 125. Differents types of local traps. Subsistence fishfarming in Africa 135
    • 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.136 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLE 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 thecontent of toxic free ammonia. 9 Increased carbon dioxide content and thus decreased pH, reduce toxic free ammonia butincrease the content of toxic free CO2. 9 Increased suspended solids from fish waste.Ö Water quality¾ 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 ofwater. 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 enoughbecause 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 airif no oxygen (Figure 126 and Photo T, p. 138). One can get oxygen in a carriage-builder who makeswelding either in a dispensary or a hospital. As much as possible, each breeder will have to be alonein his bag and, for the juveniles, one will limit the densities. However, it is true that this will increasevolume to be transported, thus, the risks of mortality are largely reduced. One should not put toomuch water in the bag. A level just above fish is enough amply. One counts, in general, 1/3 of waterfor 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 pipeon the surface, to evacuate the organic waste rejected by fish because of the stress of their captureand 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 longenough so that their digestive tract is completely empty. Water in which they will be transported willremain thus cleaner. The minimum duration of the period of fast depends on the temperature of waterand the species. In warm water, a duration from 12 to 12 midnight is sometimes sufficient. It is notnecessary for transport of short duration. One will avoid, as much as possible, to dirty the water of transport. It will thus be necessary tocarefully 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 quietduring the transport itself. Wherever possible, one will maintain fish cool during transport. There will be transport during the Subsistence fishfarming in Africa 137
    • 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.138 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLEIII. 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 thespecies 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 amanual 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 presentedaccording 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 paragraphII, p. 216). They are territorial animals. For the mouthbrooders, in fact, the males defend a territory. Forthe substrate spawners, the two parents are territorial. Generally, one can consider that the size ofthe 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 harassmentof the males at the end of incubation. If they are requested too much, the guard of the fry will beshorter 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, themales present a bright coloration. However, some non-dominant males keep a coloring close to thatof the females. It is then necessary to look at the urogenital orifice while returning the fish (Figure127, p. 140). When the breeding season comes, broodstock should be carefully selected. Only fish that areready 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, anda 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 twosexes 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 thepisciculturists, one can propose with the local services the installation of a station of stocking withfish in pond. In this case, one will choose ponds whose surface varies between 1 and 5 ares with adepth from 0.4 to 0.5 m. Some authors recommend ponds of 4 ares, allowing a higher production, byunit of area, with that of the ponds of 0.5 are. Others on the other hand recommend the use of small Subsistence fishfarming in Africa 139
    • 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.140 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLEponds from 9 to 12 m2 in which only one pair is introduced. The small size of these ponds facilitatesthe 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, allowsa production from 200 to 300 alevins per pair of parents and per month. It seems however that thefrequency of the spawns and the fry production are seriously improved while installing in these smallponds 4 to 6 females with 2 to 3 males. That would in any case avoid the absence of production bysterility of one or the other breeder. In pond of 4 ares, the stocking is made with 200 females (averageweight = 150 to 300 g) and 70 males (a.w. = 50 to 200 g), that is a density of 0.7 breeders/m2 anda 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 weightof 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 intervalof 60 days, in order to limit the frequency of the spawnings and separation of the breeders and thefry using nets of adapted meshs size, or the harvest by seining or using cast net allowing to collectall fingerlings of an average weight higher than 0.5 g. The exploitation begins 30 to 60 days afterintroducing 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 isthe optimal use of the resources of the pond, compared with the mode of breeding in more closedsystem. 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, theTable 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/dayFry 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. Subsistence fishfarming in Africa 141
    • 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.142 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLE 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 spawningsand recovery of fry, each unit being easily handle by one or two people maximum. One can also getthe fry every day with hand net. A good harvest interval will be from 10 to 14 days for females of oneto two years old. The cages generally consist of a rigid framework of wood made support or of metal equippedwith a synthetic net delimiting a volume of water and equipped with a system of floating attached tothe upper framework or supported by stakes inserted in the lakes or river at a shallow depth. Photo U. Hapas in ponds (Ghana) [© É. Bezault]. Subsistence fishfarming in Africa 143
    • 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.144 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLEThese harvests, repeated and complete, are all the more effective as they do not require draining ofthe pond, nor fishings with the seine, and thus limit the losses of offspring regularly observed at thetime of these operations. Moreover, the system with double net reduces the cannibalism exerted bythe adults, thus increasing the number of larvae produced by female. To note that cages and hapascan 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 theywill be protected. They can be used for several ends:Ö Production of fingerlingsÖ Storage of fingerlings collected in the wildÖ Storage of the associated species after captures in the wildÖ 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. Theyrequire 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 tomaintain 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]. Subsistence fishfarming in Africa 145
    • 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-146 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLEquently lower. In a more general way, the individual yield and the growth are respectively positivelyand conversely correlated with the density. In other words, until a certain threshold, more the densityis low, more the growth is fast and more the yield is low. The fishfarming systems in pond selected are polyculture dominated by the tilapia, especiallyOreochromis 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 longifilisis the second great group, the last of these species (H. longifilis) is used only in intensive systems offarming with granulated food. Although very often forgotten, Heterotis niloticus is probably the thirdfish by order of importance. By using relatively low densities, a better growth rate, a higher final weight but a lower yield canobtained. But with a higher growth rate, the duration of the cycle of farming decreases, which canallow to obtain a higher benefit at the end of the year. Experiments led in Ivory Coast showed thatthe compromise between the yield and the final average weight is for a density ranging between4 000 and 7 000 tilapia/ha (Figure 134 below). From now, it is advisable to use a densities of stockinglower than before for the fishfarming of low level of inputs. This density is of 5 000 poissons/ha, thatis 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). Thistechnique is very constraining: It is necessary to be able to get, at each beginning of cycle, catfishfry 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 forsakefry of tilapia to attack the large individuals. The value of the production fall down then since the largefish are more expensive than the small ones. If some seasons, the catfish fry are aboundant, theyare difficult to find in the wild at other times of the year. In the extensive fields, Clarias gariepinusappeared 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 5months. It is to better retain Hemichromis fasciatus, or another piscivorous Cichlidae with an easiestmanagement. This small carnivore, of size definitely lower than the tilapia, can attack only fry. It iswith this type of carnivore that the fastest growths of the tilapia were recorded (Figure 135, p. 148). Thisgives 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, Subsistence fishfarming in Africa 147
    • 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.148 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLEV. THE FOLLOW-UP OF FISH For proper management, you will need to know on regular occasions how big your fish are andhow 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 136below). The total weight of a certain number of fish can be measured. Best is to put a batch in a containeror 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 satchelor 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 donewith far less stress or damage to the fish. The easiest way to measure fish length is to use a fishmeasuring board. You can make one simply of wood. One fixes a flat ruler graduated in millimetresand centimetres on top of the horizontal board. One also fixes a small plank perpendicularly againstwhich one will bring the rule to thfe level from the zero. One make sure that the board is smooth. Acoat 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 againstthe small vertical plank, therefore on the level zero of the rule. His caudal fin well is extended andone 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 Subsistence fishfarming in Africa 149
    • 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 catchs150 Subsistence fishfarming in Africa
    • 4. FISH FARMING 5. END OF THE CYCLEfrom the pond, in order to add them with the production at the time of complete draining. If thesefishings are made in a moderated way, they make it possible to collect a total production higher thanif one practices only one draining at the end of the cycle. To collect fish, one will be able to use fishinggears (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 offreshness. Thus the fish and especially the fry which one will keep will suffer less. The material andnecessary tools for draining (shovel, basins, baskets…) will be gathered the evening before. One willbe able to store fish not consumed or sold in cages or hapas. The sale of fish will be envisaged eitherat 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 138below):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 rowat a time. Each time a row is removed of boards from the monk, one will be sure to put the screenback 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 waterjust in front of the monk. (Figure 139, p. 152). When one will be ready to harvest the rest of the fish, onewill continue to take out the boards one by one. However, it is necessary to put back the screen eachtime until the pond is empty. When all of the water is out, the remaining fis can be harvested. First thebaby fish have to be collected and then the big fish. Muddy water is bad for baby fish. So, it is betterto 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 drainingchannel outside the pond, at the end of the pipe coming from the monk (Figure 197 below). It will benecessary 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 Subsistence fishfarming in Africa 151
    • 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.152 Subsistence fishfarming in Africa
    • Chapter 10MAINTENANCE 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 arerelated 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 toensure 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 causeproblems 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 earlycontrol of disease before it becomes too serious. There are several causes of disease that may affect the fish directly or may continue to causedisease problems. Basically, any factor which causes stress or difficulty to the fish decreases itsresistance 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. Subsistence fishfarming in Africa 153
    • 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 140. Setting of fish pond: 5. End of cycle and start again…154 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMINGÖ An attack of pathogenic organisms, either externally on the skin, gills or fins, or internally in theblood, digestive tract, nervous system… Disease risks become even greater when fish undergo combined stresses, for example handlingwhen 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, trashfish or processing wastes, for example imported eggs, juveniles, or broodstock, and water from anupstream 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 ofphytoplankton and zooplankton, and exchange water if needed.Ö Keep the fish in good condition with control stocking density. Keep different sizes or sexesseparate 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 disturband stress remaining fish excessively. Apart from obvious signs such as dead or dying fish, there are many other symptoms whichshow 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 commonsituations 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 abovesymptoms of disease such as gasping at the surface or gaping mouths: the cause is prior stress (forexample 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 ofseveral weeks and some of the above symptoms are present. The cause is improper feeding and/ordevelopment of some disease organism. Subsistence fishfarming in Africa 155
    • 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.156 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMING 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 ofMetacercariae  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. Subsistence fishfarming in Africa 157
    • 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 31158 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMING If one chooses the use of additional feeding, the products showing the following characteristicswill 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 Subsistence fishfarming in Africa 159
    • 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 0.87160 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMINGor biomass (B), of fish present. This percentage is called the daily feeding rate (DFR). For example, ifDFR = 2.5 % of the fish biomass B = 80 kg, it will require 80 x (2.5 / 100) = 2.0 kg of supplementaryfeed to be distributed daily in the pond. This quantity will change during the growth of fish and thusof 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 thenext day. Conversely, if the fish quickly eat all distributed food, a little the quantities will have to beincreased 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 themwhile they eat. If the quantity of distributed food is too important, part of this one will settle at thebottom 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 ofbamboo or light wood and attach it to a stake that to insert in the ground. It is then enough to putthe food inside the square or of the circle (Figure 144 below). One will be able better to thus seethe quantity of food which settles at the bottom or to touch the bottom with the hand to see foodwhether settled. There are several occasions on which it is advantageous or even compulsory to stop feedingyour 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. Feedstuffsmust be stored with special care to prevent excessive deterioration in quality and feed losses. Themost 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 temperaturesabove 25ºC, the rates of deterioration and loss may rapidly increase. 9 Moulds (fungi) and insects (beetles, moths, weevils, etc.) may cause considerable lossesand may contaminate feeds with their metabolic by-products. High temperature and high moisturelevels 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. Subsistence fishfarming in Africa 161
    • 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 - -162 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMINGI.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 andnext 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 avoidthe formation of cracks in the dikes and in the bottom of the pond, due to the shrinkage of clays. Alight work of the surface bottom of the pond can contribute with the ventilation of the ground and thethree points mentioned above. However one should not plow deeply, because that could cause anincrease on the unproductive land surface, and an in-depth hiding of the surface layer rich in nutritiveelements. A culture (leguminous plants or food crop) can be carried out on the bottom of the pondduring a prolonged dry setting. The not collected parts will be then put into the ground before thefilling 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 cleanestpossible. This mud is composed of an accumulation of sediments of the surface layer of the bottomof the pond and organic remains. It is thus very rich in nutritive elements and can be used beside thepond as fertilizer for gardenings. It is also possible, in order not to lose these nutritive elements, todistribute 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 theinitial network will be enough, but mud will have to be rejected far and not deposited on the edgesof 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 theproduction a degradation occurs because of the digging of the banks by the population (nests of thetilapia), collapses by compressing during carried out work, a ceaseless erosion due to the waves (inthe large ponds). It is then necessary to carry out a banking up of the dikes by contribution of newground (clay) and to remake the initial slope. If necessary, it will be necessary to stop the burrowsdug 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 occursin the dike upstream of the pond plumb with the pipe. A flat rock stone or pile is deposited on thebottom 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 erosionof 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. Ifa light deterioration is noted, the rough coat should be remade. If the joints of cement are alreadyattacked, it is necessary to rejoint the stones or bricks and to replaster the unit. A defective conditionof some small boards, their replacement have to be carried out. Subsistence fishfarming in Africa 163
    • 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.164 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMINGII. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION According to the quantity of harvested fish and their destination (sale or direct consumption), itwill be possible to store fish for a later consumption, or to market it, either alive, or fresh or preservedor transformed. If one wishes to keep alive fish, one will be able to put them either in small basins or fish pondsbuilds with this use, or by using cages or grabbed (Chapter 09, paragraph III.3, p. 142). One will be ableto 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. Usuallypeople prefer fresh to processed fish. But to ensure good quality and a good price, the fish shouldbe 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 fishquickly with minimum stress. As soon as a fish dies, it starts to decompose. This process is mainlycaused by the increased activity of bacteria, which rapidly multiply within the fish under favourableconditions of food, temperature and humidity. Bacteria are especially numerous on the gills and inthe digestive tract of live fish. It is from there that decomposition will quickly spread to the wholebody as soon as a fish dies. As soon as the fish are collected and killed, it is preferable to empty them and remove all theinternal organs and blood and/or to remove the gills (or to cut the head). It is necessary to preservethe cleanliness of fish by washing them with clean water. One will avoid posing directly on the groundand one will be able to protect them carefully, for example in cases or bags of plastic to protect themfrom mud, dust, insects… If one wants to sell it fresh, it should be sold as quickly as possible. Either one collects only thequantity of fish which one thinks of being able to sell the same day, or one will keep them cool, inthe shade or covered with sheets of banana tree, of grass… The best is to obtain ice, but it is rarelythe 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 earlythe morning or even the night. Although it is to better privilege the sale of fish fresh, in some cases, the treatment of fish maybe preferable. One will be able either to expose it to high temperature by cooking it, or to lower thewater 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 bepreserved. 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 orless important. We will not go here into the details. Various techniques can be found in the technicalhandbooks 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 offish fat; Subsistence fishfarming in Africa 165
    • 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.166 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMINGIII. THE MANAGEMENT OF PONDS Proper management consists of monitoring the fish ponds regularly, keeping good records andplanning ahead for the operation of the farm. On this basis, for example one can decide when tofertilize 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 performancesof 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 thebeginning 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 presentin the pond. They are growing, although some of them may disappear, either escaping from the pondor 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 productioncycle, 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 isthe difference between the biomass at the end and the biomass at the beginning of the period. Forexample, 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 m2pond, 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/haproduced in 30 days are equivalent to (400 x 365) / 30 = 4 866.7 kg/ha/year. It may be also usefulto indicate the average daily production rate, which in this case is 4 866.7 / 365 = 13.3 kg/ha/day or1.33 g/m2/day.Ö Survival rate is the percentage of fish still present in the pond at the end of a period of time. Itshould be as close as possible to 100 percent. For example, if there were 1200 fish at the beginningof 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 theindividuals 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 isabout 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 speaksthen about daily growth rate, obtained by dividing the growth for one period given by the duration ofthis period into days. It is calculated either for one period determined during the operating cycle, orfor the totality of this cycle. Subsistence fishfarming in Africa 167
    • 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$/kg, that will make168 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMING Table XXXVI. Examples of management for 4 ponds.Harvest after 3 months (on left); After 4 months (on right). The color are related to the diffe- rent steps described in the general frework of setting the ponds. 1st exemple 2nd exemple Month Pond 1 Pond 2 Pond 3 Pond 4 Harvest Pond 1 Pond 2 Pond 3 Pond 4 Harvest 1 2 3 1 4 2 1 5 3 21st year 6 4 3 7 5 4 8 6 5 9 7 6 10 8 7 11 9 8 12 10 13 11 9 14 12 10 15 13 11 16 14 12 17 15 132nd year 18 16 14 19 17 15 20 18 16 21 19 22 20 17 23 21 18 24 22 19 Stocking fish Growing Drain and harvest Maintenance of ponds Pond not in use Subsistence fishfarming in Africa 169
    • it possible to obtain for the groups the equivalent of 2500 US$ 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;170 Subsistence fishfarming in Africa
    • 5. END OF THE CYCLE 3. PONDS, 4. FISH FARMING 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/orbartered 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 calledthe 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, shouldbe 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 areavailable. At the end of the month, one will just have to sum the different columns to get the monthlytotals. In the same way, one will be able with the end of the year, by making the total of the months, tomake an annual statement of account.III.6.THE FORMATION In order to promote and to ensure the continuity of the project correctly, trainings are necessaryfor 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 theparents.Ö Importance of the rivers: water and health Water is one of the major fields for the development of the human diseases. Several parasitesand diseases pass through the water and the lack of hygiene: malaria, cholera, schistosomiasis, toname just a few of them. We will return in the next chapter on health and the ponds. One will notdetail 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 orcome from. The ponds being water points, it is appropriate to take care of certain rules to limit theproblems 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 edgesof 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. Herbsedges 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 betteruse a latrine if it is present or to build one to at least 10 m of any edge of the ponds or enclosure andsource 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 mis the minimum to satisfy this need. In the same way, it will be necessary to avoid making its needson 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 infrastructuresthese minimal rules of hygiene. Subsistence fishfarming in Africa 171
    • 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.172 Subsistence fishfarming in Africa
    • 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. Subsistence fishfarming in Africa 173
    • 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 Resumption of a cycle « Green water » Maintenance and  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 fish174 Subsistence fishfarming in Africa
    • 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. Subsistence fishfarming in Africa 175
    • 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.176 Subsistence fishfarming in Africa
    • References Quoted here are only a few references. This list is not, of course, exhausitive. The reader mayalso 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. Subsistence fishfarming in Africa 177
    • 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/178 Subsistence fishfarming in Africa
    • Glossary A BAbiotic: Physical factor that influences the de- Bacteria: Very small unicellular organism velopment and / or survival of an organism. growing in colonies often large and unableAbundance: 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 (seeAmino 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 hydrocarbonsAerobic: 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 determinedAnaerobic: 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 (orAquaculture: 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. Subsistence fishfarming in Africa 179
    • 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.180 Subsistence fishfarming in Africa
    • 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 byEthology: Animal behavior science. the fixation by the primary producers (green plants for the major part). It passes then toEutrophic: 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 thenEutrophication: 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 fishExtrusion: 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 orFatty-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 ofFeedingstuff, 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 conveyedFingerling: 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 elementsFood 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. Subsistence fishfarming in Africa 181
    • 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;182 Subsistence fishfarming in Africa
    • 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 nutritiveNiche: 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 femaleNitrate: 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 aNitrogenize: 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 isNitrogen, 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 geneticNursery: 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 theNycthemeral: 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. Subsistence fishfarming in Africa 183
    • 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.184 Subsistence fishfarming in Africa
    • 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 ofSize, 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-inTenure: 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. YThermocline: 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. Subsistence fishfarming in Africa 185
    • 186 Subsistence fishfarming in Africa
    • Appendix Contents • Examples of files • Table of data • Some elements of the biology of the species • Biogeographic data • File of species Subsistence fishfarming in Africa 187
    • 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 255Cover photo:Ö Cichlidae, Hemichromis fasciatus in the wild, Liberia, ASUR, 2006 - © Yves Fermon, Claire Gsegner188 Subsistence fishfarming in Africa
    • Appendix 01ExAMPLES 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 Subsistence fishfarming in Africa 189
    • 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.190 Subsistence fishfarming in Africa
    • 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 byspecies, 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 Subsistence fishfarming in Africa 191
    • 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)192 Subsistence fishfarming in Africa
    • Appendix 02TABLES 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. Subsistence fishfarming in Africa 193
    • 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 16095775194 Subsistence fishfarming in Africa
    • TABLE xxxIx. The checklist of freshwater species which have been the subjectof an introduction in Africa (FAO, 2006; Fishbase, 2006).Environment (E): Found in: m = marines, s = brackishMaximal size (T): SL = Standard Length - FL = Fork Length - TL = Total Length;m = male; f = female; ns = non sexAquaculture (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 Subsistence fishfarming in Africa 195
    • 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 ns196 Subsistence fishfarming in Africa
    • 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 Subsistence fishfarming in Africa 197
    • TABLE xL (next ). 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 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 11198 Subsistence fishfarming in Africa
    • TABLE xL (next ). 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 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 Carassius carassius 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 Subsistence fishfarming in Africa 199
    • TABLE xL. (next ). 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 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 9200 Subsistence fishfarming in Africa
    • TABLE xL. (next ). 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 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 0Cyprinodontidae 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 Subsistence fishfarming in Africa 201
    • TABLE xL (next ). 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 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 217202 Subsistence fishfarming in Africa
    • TABLE xLI. List of freshwater fish used in aquaculture by country (FAO, 2006; Fish-base, 2008). 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 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 angu