Freshwater aquaculture 2nd sem (full syllabus)

POWER RANGERNOTES Freshwater Aquaculture
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Freshwater Aquaculture
FAO Definition of aquaculture : Farming of Aquatic Organisms including fish, mollusks, crustaceans and
aquatic plants. Farming implies some form of intervention in the rearing process to enhance production,
such as regular stocking, feeding, protection from predators etc., Farming also implies individual or
corporate “ownership” of stock being cultivated.
Two essential factors together differentiate (distinguish) aquaculture from capture fisheries.
 Intervention to enhance production
 Ownership of the stock
Activities constituting Aquaculture:
The following activities are considered as aquaculture:
 Rearing of fry, spat, post larvae etc., in hatcheries,
 Stocking of ponds, cages, tanks, raceways and temporary savages with wild caught or hatchery
reared juveniles to produce marketable fish/shellfish/aquatic plants/other aquatic animals.
 Culture in private tidal ponds e.g Indonesia Tambaks
 Rearing molluscs to market size from hatchery produced spat, transferred natural spat fall or
transferred part-
 Stocked fish culture in paddy fields.
 Harvesting planted or suspended seaweed
 Valliculture (Culture in coastal lagoons)
1.2 Origin of aquacutre and agricutlure
 Agriculture first developed 10000 years ago in the middle east when human population changed
from hunting-gathering to cultivating wheat and barley.Subsequently there were independednt
origins of farming cereal crops on other major land masses
 Middle east wheat and barely
 Rice cultivation began in Asia 7000 years ago
 Sorghum and millet developed in Africa
 And maize in America
 Compared to agriculture the origins of Aquaculture much later
 Common carp culture developed some hundreds of years BC in China
 The first aquaculture text book was written some 500 BC by Fan Lei a Chinese politician
 Africa, America, Australia introduced aquaculture in recent centuries.
The late origin of aquaculture is because humans who are terrestrial cannot readily appreciate parameter of
aquatic environment.
Several aquatic parameters affect aquatic organism
 Very low solubility of O2
 High solubility of CO2
 (pH) Hydrogen ion concentration
 Salinity
 Buffering capacity
 Dissolved nutrients
 Toxic nitrogenous wastes
 Turbidity
 Heavy metals and other toxic substances

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 Photo and zooplankton concentration
 Current velocity
It is difficult for terrestrial human being to appreciate influence of these environmental factors Causing
longer period for aquaculture development than other forms of food production
Construction of physical facilities building up productivity of the system and attainment of skills take
considerable period of time, therefore, aquaculture started much later than agriculture.
Further, the major consequence of late origin of aquaculture is that, relatively little genetic selection has
taken place in fish being farmed compared to plants and animals used in agriculture and animal husbandry.
Modern agriculture based on organisms vastly different from wild ancestors in heavy cases wild ancestors
don’t exist because, selection and domestication took place over thousands of yrs.
In contrast majority of aquaculture is based on wild plants and animals.
Only a few species have been domesticated. Following are the example of fish species that have been
domesticated.
 Common carp
 Atlantic salmon
 Rainbows trout
 Tilapia species
 Channel catfish
Many other aquaculture species are based on wild brood stock or larvae collected from the wild.
In some cases production cycle has not be closed i.e., the species have not been matured under captivity
and spawned under captive conditions. Therefore there is minimal potential for selective breeding because
unless the production cycles are closed selective breeding cannot take place.
1.3 State of the World Aquaculture (FAO 2010)
Aquaculture is a growing vibrant and important production sector of high protein food
 The World Aquaculture produced 55.7 million tons in 2009, valued at 105.3 billion USD
 It has grown at a steady annual growth rate of 6.1% from 2001 to 2009.
 The Per capita supply of fish from aquaculture increased from 0.7 Kg in 1970 to 7.8 Kg in 2008.
 Aquaculture production increased from 1 million MT in 1750 to 55.7 million MT in 2009.
 Growth rate of aquaculture is three times the rate of meat production during the same period.
 Capture fish production has stagnated at 90 MMT since mid 1980s therefore any further increase in
fish production has to come through aquaculture.
 Aquaculture production of plants in 2009 was 17.3 million MT valued at 4.8 billion US dollars
Aquaculture Production by Regions:
 Asia produced 88.8% of the total aquaculture production by quantity and 78.7% by value in 2008.
 China produced 62.3% of world production by quantity and 51.4% by value.
 Asia Excluding china produced 26.10% of the world fish production through aquaculture
 Top 15 produced contributed 92.4 percent of world Aqua Production
 Developing countries produced 48.62million tones of food fish valued at $ 84.03 billion

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Top five aquaculture producers countries (2009)
China was the top producer of fish through aquaculture. The other four countries in the top five positions
are given in the table below.
1) China ------- 34.78
2) India --------- 3.79
3) Vietnam ----- 2.66
4) Indonesia ----1.73
5) Thailand ------1.39
1.4 Aquaculture production by environment (2009)
Freshwater environment dominated the aquaculture production. The following table give the production
statistics by environment.
By Quantity By Value
Freshwater 60.61 56.0% V
Seawater 31.75% 30.7%
Brackish water 7.60% 13.3%
Species
Carps are the most culture species in the world with 40% of the production by volume. Other major groups
cultured include shellfish, tilapias, shrimps and prawns; and salmons. The following table shows
percentage contribution by species groups to total world aquaculture production
Sl. No. Species groups % contribution
1. Carps 39.9
2. Tilapia and other cichlids 5.6
3. Miscellaneous freshwater fish 9.5
4. Salmons, trouts, smelts 4.41
5. Shrimps and prawns 6.27
6. Oysters 7.7
7. Marine mussels 3.2
8. Scallops, Pecten 2.84
9 Clams, cockles, arkshells 7.96
10 Miscellaneous marine mollucs 1.66
Freshwater Aquaculture resources
2.1. Introduction
Freshwaters are one of the essential resources for the survival of mankind. Among other uses, freshwaters
are also use for farming of fish.
Freshwaters can be divided into
 Surface waters
 Ground water
 Ice and glaciers
 Soil moisture
Surface water can be sub-divided into

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 Rivers/streams
 SSLakes
 Ponds/tanks
 Wetlands
Following are the top 10 countries with freshwater resources
Sl. No. Country %
1) Brazil 14.9
2) Russia 8.1
3) Canada 6.0
4) United status 5.6
5) Indonesia 5.1
6) China 5.1
7) Columbia 3.9
8) Peru 3.5
9) India 3.5
10) Congo 2.3
11 Rest of the world 40.0
Out of these total resources ponds and tanks are most suitable for culture, while, pen and cage culture can
be undertaken in Lakes and Reservoirs.
2.2 Freshwater Resources of India
India is blessed with different types of freshwater resources, some of which can be utilized for fish culture.
Following are the types of water bodies found India and their extent.
S.No Type of water body Area (million ha.)
1 Ponds and tanks 2.25
2 Lakes and Reservoirs 2.09
3 Bheely and wetlands 1.30
4 Paddy fields 2.30
5 Irrigation canals 0.12
Only 45% of the ponds and tanks in India are currently utilized for fish culture
Therefore great potential for horizontal expansion exists

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Biological Resources (Species)
India is also blessed with great biodiversity of fish. Only a few of the fish found in India have been used for
fish culture or are suitable for fish culture. The following species of fish are either used for fish culture or
can be used for fish culture.
a) Carps
 India is basically a carp country
 Freshwater farming is mainly focused on carps
 Three Indian major carps viz., Catla, Rohu and Mrigal are the main species cultivated.
 The three Chinese carps – silver carp, grass carp and common carp are also used in the composite
fish culture.
 A wide range of technology for seed production and culture of the carps is available
 Carp culture expanded rapidly after 1980s in the states of Andhra Pradesh and West Bengal.
b) Air breathing fishes
 Giant murrel, striped murrel, spotted murrel, Magar ,Singhi and Climbing perch are the air
breathing fish available for culture.
 Air breathing fish are the second most popular group of fish cultured in freshwaters.
 They can withstand poor water quality
 Therefore can be grown in areas unsuitable for carp culture such as marshes and derelict water
bodies.
c) Crustaceans
 Giant freshwater prawn and the Indian River prawn are the two species of crustaceans suitable for
culture.
 They are highly priced, fast growing species suitable for export
 They can be poly cultured with the carps
 In mono-culture yields of 800 to 1000 kg/ha/year can be obtained.
d) Molluscs
 The freshwater mussels Lamellidenssp and Hyriops sp. are used for production of freshwater pearls.
e) Coldwater fish
 The Mahseers and the exotic trouts are species available for cold water fish culture
 Species Mahseers suitable for culture are Tor putitora; T. torT. khudree, T. mosal and T.
malabaricus
 The snow trout Schizothoraxsp and minor carps such as Labeo dero and L. dyocheilus are also
suitable coldwater species.
 The exotic cold water fish introduced to India are Salmogairdneri, S. truttafario and
Salvelinusfontnualis
 The tenchTincatinca is also suitable so also the common carp, Cyprinus carpio
2.3 Status of freshwater Aquaculture in India
Freshwater aquaculture has expanded rapidly in India, particularly in the States of Andhra Pradesh and
West Bengal. As stated earlier carps are the dominant group of fish cultured in India as is the case in some
other parts of Asia, particularly China. The following statistics illustrate the point.

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 Freshwater aquaculture, accounts for 70% of the total Inland production
 Aquaculture is growing at a rate of 5.6% per annum.
 Carps contribute to 90% of the freshwater aquaculture production
 Due to constant R and D and extension aquaculture productivity in India has been enhanced from a
more 500 kg/ha/yr to 2000 kg/ha/yr.
 However, the potential is yet to be reached.
The potential for increasing fish production by adopting scientific farming methods are given in the
following table.
Sl.
No.
System Potential (tons/ha/yr)
1 Composite fish culture 4-6
2 Intensive culture 10-15
3 Clarias culture 3-5
4 Sewage fed fish culture 3-5
5 Integrated fish cutlrue 3-5
6 Pen culture 1-2
7 Running Water culture 20-50 kg/m3
8 Cages 10-15 Kg/m3
By bringing more area into culture and by increasing productivity of the systems, India can substantially
increase its fish production through freshwater aquaculture.
Nursery, Rearing and grow-out ponds
3.1. Preparation and Management of Nursery, Rearing and grow-out ponds
The following definition will help to understand the concepts discussed in this units.
 Nursery ponds: Ponds where spawn are reared to fry stage. In carps it takes about 15-20 days to
grow spawn to fry size
 Rearing ponds: These are ponds where fry are grown to fingerling size. In carps it takes about 2-3
months to rear fry to fingerlings size.
 Grow-out ponds: In these ponds fingerlings are stocked and grown to harvestable size. Carps grow
from fingerlings to marketable size in about 10-12 months.
 Aquaculture as defined earlier is the Farming of aquatic organisms
 Farming implies intervention in the rearing processes to enhance production.
 Intervention strategies to enhance pond production of fish can be broadly classified as pre-stocking
management stocking and post-stocking management
3.2 Pre-stocking Management
 The ponds need to be prepared such that the pond environment provides optimum condition for
growth of the fish.
 The pond environment should be free from predators, aquatic weeds, weed fish; it should have
optimum water quality parameters and sufficient natural food should be available in semi- intensive
culture systems.

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 The steps involved in pre-stocking and post-stocking management are similar in the nursery, rearing
and grow-out ponds.
 An additional step in the pre-stocking management in nursery ponds is the eradication of aquatic
insects which predate on spawn and fry.
The pre-stocking pond management of drainable ponds, which can be dried, is as follows.
 Draining and drying
 Ploughing
 Liming
 Filling with water and
 Fertilization
Perennial un-drainable water bodies require the following additional pre-stocking management measures.
 Control of aquatic weeds
 Eradication of weed fish and predatory fish and animals.
Nursery ponds require eradication of aquatic insects as an additional pre-stocking management meature.
3.2.1 Draining, drying, Ploughing and Liming
Draining and drying
Pond needs to be drained a dried before culture operations begin
Drying facilitates in
 Oxidation of organic matter
 Degassing of toxic gases such as ammonia and hydrogen sulphide
 It kills pathogenic micro organisms
 Kills predatory and weed fish
 Kills unwanted aquatic plants
Ponds should be dried for 7-10 days till the soil cracks the ponds with clayey soil; in sandy soils they
should be dried till the soil supports a person and foot prints do not form on the soil.
Ploughing
The ponds should be ploughed using wooden ploughs or power tillers or tractors
Ploughing helps in
 Mixing up of soil which helps in oxidation of organic matter
 Proper degassing of soil from toxic gases
 Mineralization of nutrients.
Liming
The productivity of fish ponds depends on soil qualities such as
 Texture
 Water retention
 pH
 Organic carbon
 Available nitrogen
 Available phosphorous

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Pond bottom is important for productivity since process of mineralization of organic matter and release of
nutrients to the overlying water takes place
Liming helps in improving the quality of the pond soil, thus enhancing productivity.
It also corrects soil pH; the desirable pH is 6.5 – 7.00
A range of liming materials are used such as
 Agricultural lime or calcite (CaCO3)
 Dolomite [CaMg(CO3)]
 Calcium hydroxide/slaked line Ca(OH)2
 Calcium oxide/quicklime - CaO
The dose of a particular variety of lime depends on its effectiveness and soil pH
Generally 200-500 kg/ha of line is used for application to pond soil
After application, the lime should be mixed with the top soil with light ploughing.
Quick lime is preferred for applying to soil and calcite agricultural lime for application to water after
stocking of the ponds
Liming helps in
 Correcting soil pH
 Mineralization of organic matter
 Release of soil sound phosphorous to water
 Disinfection of the pond bottom
3.2.2 Pond fertilization
 Fry and fingerlings of most fish such as carps feed on zooplankton
 Sustained zooplankton production in ponds depends on good phytoplankton and bacterial base
 This is maintained through adequate availability of nutrients such as Nitrogen, Phosphorous carbon
and micronutrients in ponds.
 Natural availability of these nutrients in ponds will be inadequate.
 Hence they need to be added through external sources for sustaining good plankton growth
 Nutrients are added to water through organic manures and inorganic fertilizers.
Organic manures
 Organic manures are are rich in carbon and contain nutrients such as N and P in small amounts.
 They decompose slowly and release the nutrients slowly
 They promote the growth of zooplankton through saprophytic food chain
 They promote sustained growth of phytoplankton and zooplankton for longer periods of time
 Several types of manures such as cow dung, poultry litter, pig dung, horse dung etc., can be used to
fertilize fish ponds.
 Most common manures used in fish ponds are cow dung and poultry manure
 Raw cow dung is generally applied at a rate of 5-10 tons/ha 15 days before stocking.
 It can be also applied in phases; 2/3 of the amount as basal dose and a second dose after a week of
stocking
 Poultry manure is 2-3 times richer than cow dung in the content of nitrogen and phophorus.
 Hence half the dose of cow dung is used, when poultry manure is applied to the ponds.

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Inorganic fertilizers
 These are concentrated forms of nutrients such as N and P
 Urea or ammonium sulphate is used as a source of N while single or triple super phosphate is used
as a source of P
 Inorganic fertilizers promote the production of phytoplankton on which zooplankton production
depends.
 Their action is very fast and when used in excess quantities promote blooms of undesirable Blue
Green Algae (BGA)
 Hence they should be used cautiously in fish ponds
 A combination of organic manure and inorganic fertilizers will promote the growth of
phytoplankton quickly which will sustain for a longer period of time because of fertilizing with
organic manures.
3.2.3 Control of Aquatic Weeds
Large earthen ponds are usually infested with submerged, emergent floating and marginal weeds.
Weeds cause several problems in fish ponds
 They compete for nutrients with phytoplankton thereby reducing the natural productivity fo the
ponds.
 Prevent light penetration and suppress the production of phytoplankton
 Cause oxygen super saturation during day and oxygen deficiency during night
 Harbor aquatic insects and predatory fish
 Hinder free movement of fish and reduce their living space
 Cause problems during harvesting by hindering netting operations.
 Increase siltation in the pond, reducing pond depth over a period of time
Therefore growth of aquatic weeds needs to be controlled and their density reduced in fish ponds
Aquatic weeds can be controlled by employing methods such as
 Manual
 Mechanical
 Chemical and
 Biological
The method selected depends on factors such as
 Pond size
 Extent of weed infestation
 Time available
 Cost
3.2.4 Eradication of Predatory and Weed fish
 Predatory fish severely affect survival of fish primarily in nursery and rearing ponds.
 Weed fish compete with stocked fish for food, space and oxygen and result in reduction in
production of desirable fish.
 Common predatory fish are murrels (Snakeheads), Catfishes such as Wallago attu, Clarias
batrachus, Heteropneustis fossilis, Ompak sp. Etc.,
 Weed fish include Puntius, Barbas Danio, Aplocheilus, Anabas etc.,

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 Most predatory and weed fish breed prior to the onset of carp breeding
 They infest the ponds before carp fry and fingerlings are stocked
 Hence their eradication prior to stocking of carps is necessary
 Dewatering followed by sun drying is most effective way to control weed and predatory fish.
 In ponds which cannot be dewatered, piscicides are used.
A suitable piscicides should have the following characteristics
 Effective at low dose
 Not injurious to people and animals
 Doesn’t make fish unsuitable for human consumption
 Gets detoxified quickly
 Easily available and economical
Types of piscicides
Following are the three types of piscicides that can be used to eradicate weed fish and predatory fish
 Plant origin
 Chemicals
 Pesticides (Chlorinate hydro carbons and organophosphates)
Piscicides of plant origin
Derris root powder
 Rotenone is the active ingredient
 It is a contact poison
 Lethal to other organisms also such as zooplankton, Benthos and insects
 Dosage is 4-20 ppm (mg/l)
 The powder is mixed thoroughly with water and sprayed all over the pond
 It is effective only on sunny days when the temperature is above 250C
 It is less effective in cold waters.
Mahua oilcake
 The active ingredient is saponin
 It causes lysis of the RBC and kills fish, frogs, snakes and turtles
 Dosage is 250 ppm
 The cake is soaked in water for 2-3 hrs and applied all over the pond.
 Detoxification takes about 25 days
 The toxicity can be reduced to 10 days through aeration and application of oxidizing agents.
The other less widely use fish toxicants of plant origin are
 Tea seed cake – 60 ppm
 Tamarind seed husk – 50-100 ppm
 Jaggery – 1%
3.3.1 Stocking
 Nursery, rearing and stocking ponds are stocked with spawn, fry and fingerlings respectively. They
need to be acclimatized in ponds before stocking to prevent abrupt changes in water quality which
will stress them resulting in poorer survival.

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Generally mono-culture is followed in nursery and rearing ponds, while poly-culture of carps in
followed in grow-out ponds. When rearing space is limited polyculture is also followed in the
rearing ponds.
Grow-out culture of carnivores is done under monoculture.
The stocking densities followed vary according to the level of management that can be under taken.
For example when carp spawn are stocked in earthen nursery ponds, a stocking density of 300 to
500 numbers per m2 of pond area, while, stocking densities of 1000 t0 2000 numbers per m2
followed when they are stocked in cement tanks where, higher level of management is followed.
Rearing ponds are stocked with carp fry @ 20 to 30 numbers per square meter in rearing ponds
while carp grow out ponds are stocked @ 5000-1000 numbers per hectare when polyculture is
followed.
3.3.2 Supplementary feeding
When fish are stocked at high stocking densities, the natural food produced through fertilization and manuring may
not be sufficient to sustain high growth in shorter period of time. Hence,the stock has to be fed with supplementary
feeds. Commonly, supplementary feeds such as mixture of rice bran or wheat brawn mixed with oil cakes such as
groundnut cake or mustard cake or cotton seed cake and other cakes are used in a ratio of 1:1. In order to improve the
quality of feed to get better growth and production, extra ingredients such as fish meal, soya flour, vitamin and
mineral mixtures could be added to the feeds. The feed mixture is generally mixed with appropriate quantity of water
and made in dough which is then shaped into a form of ball or cake is either broadcast into the ponds or kept in
feeding trays at severalplaces in the pond.
Feeding rates vary according to the size of the fish. Spawn are fed at a rate of 8-10% of the biomass, while fry when
stocked in rearing ponds up to fingerlings stage are generally fed @ 6-8% of the standing crop. In grow-out ponds
the fish are fed initially at a rate of 5% which is gradually decreased to 2-3% biomass till harvest. Periodic sampling
of the stock is necessary to estimate the biomass and adjust feeding rates.
3.3.3 Supplementary fertilization
Ponds are fertilized prior to stocking fish with manures and fertilizers, when they are applied as a basaldose. Due to
overfeeding by fish on the plankton and other natural fish food organisms, the plankton biomass may get depleted. In
order to maintain the crop of fish food organisms, supplementary feed post-stocking may be required. When the
water starts to lose its plankton turbidity, amounts less than basal dose of fertilizers need to be applied to ponds and
fortnightly intervals. For example in carp rearing and grow-out ponds are manured with cow dung as a basaldose of
3-4 tons/ha. The ponds are subsequently fertilized with cow dung at a dose of 0.5 tons/ha at fortnightly intervals.
However,supplementary fertilization should be followed with caution since application of excess of fertilizers and
manures may lead to poor water quality of the pond, or undesirable blue green algae such as Microcystis may
develop which apart from being toxic, will not form food for the fish
3.3.4 Water quality management
Good growth and production of fish not only depends on availability of good quality feed, but also and the quality of
the water in which they live. Physico-chemical properties of the water should be within the range of tolerance of the
species being cultured.
Normally water quality will not be an issue with lower stocking densities and lower yields (extensive and lower level
of semi-intensive culture). However,when higher stocking densities are followed, water quality tends to deteriorate,
particularly when the stock grows and biomass increase
The most important water quality parameters are the dissolved oxygen. Oxygen dissolves from the atmosphere and
also produced by photosynthesis phytoplankton and higher macrophytes which produce liberate oxygen during the
day but consume oxygen during night. The levels of DO in culture systems should be above 5 mg/L. When oxygen

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tends to fall below this level, which usually occurs during night, aeration of the ponds becomes necessary. Various
types of aerators are commercially available, which may be expensive. A simple way to aerate is to circulate the
pond water such that bottom water comes to the surface and surface water goes to the bottom. This can be done using
a pump whose intake (foot valve) is lowered into the pond and water is pumped such that the water splashes back
into the same pond. Aeration may also become necessary during cloudy weather since lack of sunlight prevents
photo-synthetic production of oxygen by the algae and higher plants.
Accumulation of metabolites and decayed matter will also result in poor water quality in ponds. Ammonia may get
accumulated which is toxic to fish. In order to maintain water quality, water exchange may be required to be carried
out. The frequency and amount of water to be replaced with freshwater depends on the quality of the water. This
requires experience as well as analysis of the water quality.
Cultivable fish and their culture methods
4.1 Culture of indian major carps and exotic carps
Carps are major source of animal protein for millions of people in Asia. World cyprinid aquaculture
production in 2009 was 22,228,344 metric tons valued at USD 29,399,045. They are the most cultured
species in the world with 40% production by volume. The major countries producing carps through
aquaculture are China and India.
Carps belong to the family Cyprinidae which is typically a freshwater group with very wide distribution.
They are distinguished by the presence of pharyngeal teeth in one to three rows with not more than eight
teeth in any row. Lips are usually thin and an upper jaw that is usually bordered only by premaxilla.
There are about 1600 species in the family cyprinidae making it the largest family of fish. Despite large
number of species of carps only 29 species of carps is cultured globally (FAO statistics list the production
figure for 29 species only). There are only six species which are cultured on a large scale. They are grass
carp, silver carp and common carp in China and Catla, rohu and mrigal in India and elsewhere. The former
three species are termed the Chinese carps and the later three as the India major carps. Together they are
called major carps since they grow to relatively large size.
Biology
Cultured carps are all riverine , typically found in large river systems. The food habits of species differ
from each other.
Summary of feeding habits of the major Carps
Species Feeding habit
Silver carp Zoo- and phytoplankton, filter feeder, prefers phytoplankton, surface
feeder.
Grass carp Omnivorous, prefers higher aquatic plants and submerged grasses
Catla Plankton feeder, prefers zooplankton and surface feeder
Rohu Omnivorous planktophage; predominantly a column feeder
Mrigal Omnivorous, prefers detritus, predominantly a bottom feeder
Common carp Omnivorous, predominantly feeds on benthic worms; a bottom feeder
All the major carps grow to about 1m in length. Generally Chinese carps grow to a larger size than Indian
major carps. Under culture conditions they are harvested in their second or third year, often at a weight
approaching 2-3 kg.
4.1.1 Farming of carps
The distinctive features of carp culture are that the practices
 Tend to be semi – intensive
 Almost always use poly-culture
 May be integrated with other forms of farming (Integrated systems)
 Are carried out in ponds and pens but rarely in cages and raceways.

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Poly-culture is thought to have originated in China. Polyculture is farming of two or more compatible
species with different feeding habits in the same pond to maximize utilization of all the niches (food and
space) of a pond. It maximizes the synergistic fish-fish and fish–environment relationships and minimizes
antagonistic relationships. Under same level of management production will be generally higher in
polyculture systems and more number of species can be grown for market than in monoculture systems.
A concerted experimental effort occurred in India to develop suitable polyculture system using both Indian
and Chinese carps. The basic species combination in the Indian composite polyculture system was catla,
rohu, mrigal, silver carp, grass carp and common carp. At a stocking density of 5000Nos., / ha (120-250
kg/ha) the yield was nearly 9 MT/ha/yr, when fertilized and provided with simple supplementary feed such
as mixture of rice and oil cake. The polycutlure of Indian and Chinese carps together was termed
“Composite fish culture”.
Despite experimental findings in both India and China farming practice tends to depend on two or three
species of either Indian or Chinese carps. This trend is primarily influenced by consumer preference of
indigenous species.
Both in India and China two or three species of either Indian or Chinese carps are polycultured. The
dominate species in India is rohu and in China it is silver carp.
Over the last three decades carp farmers have developed their own protocols. This is best exemplified in
Andhra Pradesh where only two species of Indian major carps namely rohu and catla are cultured. Rohu is
the dominant species in polyculture which is stocked at 80% of the stocking density, catla being stocked at
20%. The pond area often exceed 1ha and the ponds are stocked with 6-12 month old (100-150g)
juveniles@ 5000/ha. Ponds are generally fertilized with poultry manure and inorganic fertilizers. They are
provided with supplementary feeds such as simple mixture of rice bran and oilcake. Production in Andhra
Pradesh averages about 8000 kg/ha with a range of 5300-14620 kg/ha. Fish are harvested when they are
more than 1.5 kg in size.
On the other hand, Chinese carps are grown along with common carp in China. There are also regional
differences in Chinese carp culture. The most important difference is in the dominant species in
polyculture. For example silver and bighead carps dominate in central China, while grass carp dominates in
Southern China.
The wide range of practices adopted by the farmers makes it different to assess potential yields from
different systems. For example in Andhra Pradesh where two operational systems are observed – one
utilizing two species (Rohu and Catla) and other utilizing three species (rohu, catla and mrigal) gross yields
ranged from 1730 to 14830 kg/ha/yr. There was no evidence to indicate that two or three species system
performed better than the other.
4.1.2 Culture Practice
Carps are mostly cultured in three stages namely.
 Nursery Phase
 Rearing Phase and
 Grow – out phase
Nursery phase
Carp spawn, 72-96h old are reared up to fry size (25mm) in this phase in small ponds of size 200 to 1000

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m2 with a depth of 1.0 – 1.5m. The rearing period lasts for about 15-20 days.
All the pond preparation procedures explained in the previous unit are followed. The steps followed are
 Drying – 3-5 days
 Ploughing
 Liming
 Fertilization
 Eradication of insects
 Stocking
 Supplementary feeding and
 Supplementary fertilization
Additional steps in undrainable ponds include
 Control of Aquatic weeds
 Eradication of predators and weed fish
Pond Fertilization:
 Nursery ponds are fertilized with inorganic and organic manures to promote production of phyto-
and zooplankton. The fry of carps feed initially on zooplankton such as rotifers and cladocerans
 The ponds are first applied with lime @ 200-500 kg/ha and ploughed into the soil lightly. The
ponds are then filled with water to a depth of 1.00 to 1.5 m. One week post liming cow dung is
applied @ 5-6 tones/ha or with poultry manure @ 2-3 tones/ha, a fortnight before stocking.
Control of aquatic insects
 Insects and their larvae feed as carp spawn and fry or sometimes kill them by piercing their bodies.
They also compete for food and space leading to poor survival of the stocked spawn. The
population of insects increases enormously post fertilization. They multiply rapidly and spread from
pond to pond by flying.
 Application of soap oil emulsion @ 56 kg soap to 18 kg cheap oil is a simple and effective means
of insect control. These insects are air breathing. The soap oil emulsion floating at the surface of the
water chokes their respiratory apparatus when the swimming up to the surface for breathing.
Stocking:
 The spawn ( 72-96h old) are transferred from hatcheries to nurseries during cool hours preferably in
the morning.
 The optimum stocking density recommended for earthen nursery is 3-5 million /ha
 Higher densities of 10-20 million/ha can be followed for nursery rearing in cement tanks.
 Mono-species culture is usually followed at nursery stage. If rearing space is limited polycutlure
can be followed.
Supplementary feeding:
 Spawn are fed with finely powdered mixture of oilcake and rice bran in 1:1 ratio to supplement the
natural food.

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 They are fed @ 600 g/lakh fry for the first five days and 1200 g/lakh spawn for subsequent days in
two equal installments during morning and evening hrs. In about 15-20 days fry attain a size of
about 25mm at which size they are transferred to rearing ponds.
Harvesting fry :
 Harvesting is done by repeated dragging with a fry net of 1/8 inch mesh. The quantity harvested is
measured in perforated cups.
 Number harvested is estimated by multiplying the number of cups and average number of fry per
cup.
 Survival rates vary from about 40-50% from June to September. 2-3 crops of fry can be raised in
earthen ponds and 4-5 crops in concrete tanks.
4.1.3 Production of carp fingerlings
 Though a crucial phase for production of good quality seed of carps, this stage is often ignored due
to paucity of space. Farmers often stock the grow – out ponds with fry resulting in poor survival.
 Ponds of size 500-2000 m2 are generally used for rearing carp fry to fingerling stage.
 The control of aquatic insects is not necessary in rearing ponds, but control of weeds, predators and
weed fish is necessary in undrainable ponds. The pond preparation steps are similar to those of
necessary ponds.
Pond fertilization
Ponds are manured with cow dung @ 3-4 tons/ha as basal dose 7-10 days before stocking and one week
after liming at a dose of 200-500kg/ha. Thereafter cow dung is applied @ 500 kg/ha every fortnight. When
poultry manure is use half the dosage of cow dung is used.
Additionally urea and single super phosphate @ 10 and 15 kg/ha are used for sustaining plankton growth.
Stocking
Fry (25mm) are transferred from nursery to rearing ponds, during cool hours. Either monoculture or
polyculture is followed. Recommended combined stocking density is 2-3 lakh/ha
Supplementary feeding
Fry are fed @ of 8-10% of biomass for the first month, followed by 6-8 and 4-6% during the second and
third month. The commonly used feed a mixture of rice bran and oil cakes particularly groundnut oil cake
in the ratio of 1:1. Other ingredients such as fishmeal, soybean floor etc., can be incorporated for
improving feed quality.
Post stocking pond management
Maintaining water level of 1.0 – 1.5m and intermittent fertilization as mentioned earlier are the other
management measures required.
Harvesting
Fingerlings are harvested after 2-3 months at a size of 80-100 mm/ 8-10g. Survival rates of 70-80% can be
obtained with good management measures.

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Transportation of fry and fingerlings
Long distance transport of fry and fingerlings can be done by packing them in sealed polyethylene bags
filled with water and pure oxygen in the ratio of 1:2 to 1:3 water to oxygen.
The number of seed per bag depends on the size of the seed and duration of transport.
Fry and fingerlings are conditioned by crowding them in hapas and starving the seed for 24-48 hours. They
are then packed during cool hours in polythene bags with water and oxygen. The polyethylene bags are
supported by suitable boxes/bags to prevent damage during transport. Ice can be added to bags to reduce
temperature and metabolic rate of the fish.
4.1.4 Grow-out culture
Carp culture is the main stay of Indian aquaculture. Catla rohu and mrigal are cultured traditionally in ponds and
tanks due to their higher growth and consumer preference. Due to their compatible nature all the three species are
grown under polyculture. Catla is a surface feeder feeding predominantly as zooplankton while rohu is a column
feeder. It is an omnivorous planktophage. Mrigal is a bottom feeder feeding on benthic detritus. The exotic silver
carp, grass carps and common carp are also stocked along with the three Indian major carps.
India possesses 2.3 million ha of potential freshwater resources in the form of tanks and ponds, but utilize only about
40% on the average for carp farming. The average national carp culture productivity is only 2 tons/ha/yr while the
potential production is be 3-4 tones under semi-intensive culture. Hence there is an enormous scope for increasing
carp production in India. This is possible through bringing more average under culture and also by following
scientific technology of carp production.
The scientific carp culture practices involve the following steps.
Pre-stocking preparation
Control of aquatic weeds and eradication of predators and pest fishes are one of the important steps for achieving
higher production. The ponds should be dried until the bottom soil cracks. Application of lime @ 200-500 kg/ha and
ploughing the soil removes obnoxious gases,oxidizes the organic matter in ponds, sterilizes the soils and kills
unwanted animals.
After filling the ponds to a depth of 1.5m the ponds should be manured with cow dung @ 3-4 tones/ha as a basal
dose 15-20 days before stocking. Alternatively, poultry dropping @ 1.5-2.00 ha/ha can be used. If mahua oil cake is
used for eradication of predatory and weed fish the basal dose of organic manure is avoided. 15-20 days after
application of manures the ponds are ready for stocking.
The carp culture ponds are stocked with surface,column and bottom feeders at proper ratios to utilize all the pond
niches efficiently. 30-40% of surface feeders,30-35% of column feeders and 30-40% of bottom feeders should be
stocked. Grass carp may be stocked if terrestrial grasses or aquatic weeds can be supplied from outside.
The grow–out ponds are stocked with fingerlings of 8-10g after proper acclimatization. A stocking density of 5000
fingerlings/ha is recommended to get a production of 3-5 tonnes/ha/yr. The density could be raised to 8,000 – 10,000
figerlings/ha for achieving production of 5-8 tons/ha/yr. The stocking density depends on the level of management
and input use.
Post stocking management
The management of carp, ponds after stocking involves intermittent liming and fertilization, water management and
health care.
In average production ponds cow dung is applied @ 500 kg/ha/fortnight, along with 15 kg/ha single superphosphate
and 10 kg/ha area. However the dose and frequency of fertilization depends on plankton production and water
quality. Other manures such as poultry manure or duck droppings can be used at half the dose of cow dung.
Supplementary feeding is provided to the stocked fish. At high stocking densities natural food produced through

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fertilization will not be sufficient. Supplementary feeds could be simple mixtures of rice bran and oil cake in a ratio
of 1:1. The quality of supplementary feed can be improved by mixing fishmeal and soya bean meal with vitamin and
mineral mixture to the simple mixture of rice bran and oil cake. Commercial fish pellets are also available which
may give better yields. The carps are fed @ 5% of the body weight for first month which is gradually decreased to 3-
2%. The biomass of the fish should be assessed monthly and feed ratio should be adjusted accordingly. The daily
ratio is split into two doses and fed in the morning and evening. The mixture is made into dough by adding correct
quantity of water and making in to balls.
The balls are kept in feeding trays at different places in the pond. In Andhra Pradesh simple mixtures of rice bran and
powdered ground nut oil cake are filled into gunny bags with small holes, which are hung in the ponds on poles at
different places. Fish will nibble at the holes and get feed. When grass carp is stocked in the ponds aquatic weeds
such as Hydrilla, Ceratophyllum, Najas, duck weeds or tender terrestrialgrasses should be provided.
Harvesting
The carps take about 10-12 months to grow to marketable size when fingerlings of 8-10 g are stocked. In this period
catla grows to a size of about 1 kg, while, rohu and mrigal attain a size of about 600-750g. Silver carp grows to more
than 1 kg while grass carp can grow to a size of 3-5 kg if fed at 100% of its body weight. The fish are usually
harvested by large seine nets by repeated dragging. If the ponds are drainable a finally drain harvested in carried out.
A production of 3-5 tones/ha/yr can be obtained through scientifically managed semi-intensive culture of carps.
4.2 Catfish culture
Owing to their unique taste and texture, cat fishes are considered a delicacy by some consumers. However,large
scale commercial culture of these fish is currently not being carried out in India, except the culture of recently
introduced exotic Thai catfish Pangasiodonhypothalamus. Experimental and pilot scale culture for some native fish
such the magur (Clarias batrachus), singhi (Heteropneustis fossilis) and the butter cat fish (Ompak bimaculatus) has
been developed by severalresearch Institutes in India. Government of India has now identified catfish farming as a
national priority as a part of diversification of aquaculture practices.
Air breathing cat fish such as magur and singhi have a greater potential for culture in shallow, swampy, marshy and
derelict water bodies. Non-airbreathing catfish such as Pangasius pungasius, Wallago attu, Ompak sp, Mystus sp., etc
can be grown in normal pond conditions. However,culture techniques for these species needs to developed.
4.2.1 Culture ofMagur (Clariasbatrachus)
This is the most popular catfish owing to its good taste and texture. Being an air breathing fish, it can survive in poor
water quality conditions. This fish can be cultured at very high stocking densities. The fish can be sold live and
hence fetches higher price than carps.
The techniques for breeding, seed production and grow out of magur have been standardized. A few farmers have
already adopted these techniques in different parts of the country.
Larval rearing
The aerial respiration in the larvae starts 10-12 days post hatch. They are obligate air breathers and hence need
atmospheric oxygen irrespective of dissolved oxygen. Since they lie at the bottom and have to make vertical trips to
surface for breathing air the water depth is an important factor to be considered.
Initially, a water depth of 8-10 cm is kept in the larval tank to avoid loss of energy spent for making vertical trips.
The depth in gradually increased with the increase in rearing period.
The Hatchlings are stocked @ 2000 – 3000 / m2 in well aerated rearing tanks. They subsist on yolk for about 3 days.
Subsequently they are fed with live plankton or Artemianauplii. 50% of the water is exchanged on alternate days.
They are reared for 12-14 days when they reach a size of 10-12mm size (30-40mm). They are harvested and
transferred to outdoor rearing tanks and stocked @ 200-300 Nos./m2 . The tanks are fertilized in a similar manner as
carp rearing tanks. Floating weeds such as water hyacinth or duck weeds are provided as shelter. The fry are fed
formulated crumbled feed pellets of 35% protein or a mixture of finally mined trash fish/molluscan meat and rice
bran @ 1:1 ratio, @ 5-10% of the biomass. The fry grow to a fingerling size of 3-4 cm (0.8-1g) in about 30 days.
They are harvested by draining the tanks.

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Grow–out culture
Grow out culture is carried out in earthen or stone pitched ponds. Since magur may migrate out during rainy season,
fencing is provided around the ponds. They are stocked @ 50,000 – 70,000 finger lings/ha. The ponds are fertilized
in a similar manner as carp ponds.
The fish are fed mixtures of groundnut oil cake,rice bran, fish meal/trash fish. They are fed @ 3-5% biomass in the
form of dough placed in baskets or in pellet form at different places in the pond. The feed should contain 30-35%
protein. The tanks should be covered with nets to protect them from predation by birds. Broken pipes or tiles are
provided as shelters to reduce cannibalism. Water loss through evaporation should be compensated periodically by
letting the water in.
Magur attains marketable size of 100-120g in 7-8 months. Harvesting by netting is difficult, hence ponds needs to be
drained and fish handpicked. Average production of magur from this system is 3-4 tones/ha/7-8 months.
4.2.2 Culture ofstinging catfish
Heteropneustis fossilis commonly known as singhi has a good potential as aquaculture candidates. This is an air
breathing fish which can thrive well in shallow derelict water bodies with poor water quality.
Larval rearing
The larvae are very delicate and require good water quality at this stage. The optimum DO is 5-6 ppm; pH 6.5-7.5
and water temperature 26-28OC. Initially the larvae are fed mixed zooplankton, Artimia nauplii and tubifex worms.
Regular cleaning of debris, uneaten food and dead or weak larvae is necessary. They grow to 12-15 mm during 14-
15days rearing period.
After attaining fry stage they are stocked in well prepared small, cement tanks. The water depth should be shallow to
allow fry to come up for breathing. The fry are stocked @ 300-500/m2. Finely minced trash fish, molluscan meat
with rice bran in equal proportion is fed to the fry. In about a month they reach fingerling size.
Grow-out culture
Singhi can be grown in monoculture or poly culture with carps and magur. It is stocked in well prepared ponds and
fed with compounded diets or slaughter house waste/trash fish, silkworm pupae. Its production potential has been
estimated to be 4-15 tons/ha in 4-12 months culture under AICRP.
Other species of catfish : Other species of catfish such as Pangasius sp., Wallago attu, Ompak sp., Mystus sp., Rita
rita and Bagariusbagarius grow to large size and have good market demand. It is necessary to have greater thrust on
research to develop technologies for culture of these catfish.
4.3 Freshwater prawn cutlure
The giant freshwater prawn Macrobrachiumrosenbergii is one of the highly priced species cultured in freshwater.
It is distributed in the major river systems of the country. Although the freshwater prawns live in freshwater their
larvae require brackish water to survive and grow. Adults migrate to estuaries to breed and post larvae migrate back
to fresh waters. Freshwater prawns are omnivores,their feed includes decaying plants and animals at the bottom. The
food in the stomach can be viewed through the transparent carapace. They are cannibalistic in nature and attack
newly molted and weak prawns. Therefore provision of adequate feed and shelters need is essential in their culture
systems.
The Biology and management ofsize variation
Size variation in the population, particularly of males – a typical characteristic of Macrobrachium rosenbergi - is a
major obstacle to prawn culture and its profitability. The prize of the prawn depends on its size and those below
minimum size are discarded by growers. The harvest consists of a large fraction of small unmarketable individuals
and a fraction of large prawns. However,removal of large prawns leads to a rapid compensatory growth of the
smaller individuals. Size variation is the result of heterogeneous individual growth (HIG) which is a complicated
biological characteristic of the giant freshwater prawn. It reflects a complex population structure composed of three

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sexually mature morphotypes (small male, orange claw male and blue claw male), which differ in their morphology,
physiology and behavior and transform from one morphotype to another. The growth regulation of prawns –
suppression as well as enhancement - is achieved by means of social interactions among individuals.
The blue claw (BC) male is characterized by its extremely long claws. The stunted small male (SM) is differentiated
from younger juveniles by their greater age. The intermediate orange clawed (OC) male has golden colored claws
which are 30 to 70% shorter than those of the blue claw males. Harvested mature prawn populations are composed of
three distinct male morphotypes (sM, OC and BC) which represents the normal male developmental pathway from
SM to BC through OC.
Prawn populations display a disproportionate increase in size variation with time because individual prawns grow at
different rates i.e., they show heterogeneous individual growth. The fastest growing individuals are called “Jumpers”
and slowest growing individuals are called “laggards”. When jumpers are remove from the population some laggards
will transform into jumpers. In other words presence of blue claw male suppresses the growth of SM and OC
individuals. When BC males are removed some OC males transform to BC Males and some SMs become OC males.
Then harvesting of larger prawns will result in faster growth of small individuals resulting in higher yields.
Grow – out systems
The management of size variation is an extremely important and complicated aspect of culture of freshwater prawns,
because of the uneven growth rate of individual prawns especially males.
4.3.1 Systems ofmanagement for reducing HIG
There are three to four systems of grow-out culture of freshwater prawns,the are:
1) Continuous System:
This system involves regular stocking of post larvae (PL) and selective harvesting of prawns of marketable size.
There is no defined “cycle” of operation and ponds are drained only occasionally. This system can be practiced in
places where there is year – round water availability and optimum temperature is present throughout the year. Also if
selective harvesting is inefficient, large dominant prawns remain and have negative impact on the PLs which are
introduced at subsequent stocking, resulting in lower average growth rate.
Long terms continuous system is not recommend for above reasons.
2) The Batch System:
Batch system consists of stocking the pond once and allowing the individuals to grow to average market size. The
ponds are drained totally and harvested HIG remains as a problem in this system.
3) The combined system:
The ponds are stocked only once. Cull – harvesting starts when the first prawns reach marketable size, removing the
fast growing prawns for sale and leaving the smaller ones to grow with less impact of HIG. After several cull-
harvesting, the ponds are finally drain-harvested. The total cycle usually lasts for about 9-12 months in tropical
regions. This is a recommended system for culture of freshwater prawns for better management of HIG to more
uniformed sized prawns.
4.3.2 Farming intensity
Depending on the stocking density and management of the system three levels of culture are recognized.
1) Extensive prawn culture:
In this system prawns are reared in ponds, reservoirs, irrigation ponds and rice fields. Production is less than 500
Kg/ha/yr. Stocking is mostly form wild sources. They are stocked with either PLs or juveniles at a density of 1-4/m2.
There is no water quality management. Organic fertilization is rarely applied and there is no supplementary feeding.
2) Semi – intensive prawn culture:
This system involves stocking of PLs or juveniles usually from hatcheries at a density of 4-20/m2 in ponds.
Fertilization is used and balanced feeds are provided. Predators and competitors are removed and water quality and
health are monitored. This level of culture is most common in tropics and yields more than 500 kg/ha/yr.

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3) Intensive prawn culture:
The prawns are reared in small earthen ponds or concrete tanks up to 0.2 ha, provided with high water exchange and
continuous aeration. They are stocked @ 20/m2. High degree of management is required. Nutritionally balanced
feeds are provided. A strict control over all aspects of water quality is maintained. This system requires more
research particularly on the management of size variation. Therefore semi-intensive mono-culture of prawns is
currently not recommended.
4.3.3 Semi – intensive mono culture ofFreshwater prawns
Pond preparations:
After the final harvest of last batch ponds are drained to remove all predators, pond banks or dykes are repaired and
inlet and outlet screens are checked. The ponds are dried for 2-3 weeks. If sediment has built up over years they
should be removed by scraping the pond bottom. The bottom is ploughed during drying to oxygenate the pond soil.
The pond bottom should be applied with lime @ 1000 kg/ha.
If the ponds cannot be dried, predatory and weed fish can be controlled by applying mahua oil cake @ 2000 – 2500
kg/ha of water (200-250 ppm). The use of pesticides is not recommended to eradicate predators since they are
potentially toxic to prawns. Also they may bio-accumulate in prawn tissues. These will be dangerous to consumers.
The ponds are fertilized with cattle manure @ 1000-3000 kg/ha. This will increase the benthic fauna which form
food of prawns.
Stocking:
Ponds are stocked with PL/Juveniles immediately after filling them with water. This has no predators and no photo-
synthetically induced pH changes. There may be slight reduction in growth rates,but increased survival will offset
the reduced growth. Stocking rate will depend on the level of management and harvest desired. In semi – intensive
culture a stocking density of 4 and 20 PL/m2. The lower stocking rates will result in larger sized prawns at harvest.
Feeding and fertilization:
Adequate phytoplankton density should be maintained to provide cover and control the growth of weeds. Often it is
unnecessary to fertilize the ponds intermittently, since feeding alone will not provide adequate nutrients for plankton
growth. Sandy soils may need fertilization. 25 kg/ha/month triple superphosphate will keep the water green. Animal
manures can be used to promote benthic biofauna which are an important part of the ecosystem. However instead of
animal manures other organic materials such as distillery byproducts or other plant residues such as oil cakes are
better organic fertilizers. Commercial pellets can be used as supplementary feeds. Prawns are initially fed @ 8-10%
biomass which is gradually reduced to 2-3%.
Harvesting:
When the larger prawns reach harvestable size they are caught by seining and sold. Cull harvesting can done to
regularly remove larger prawns after 10-12 months the ponds are drained harvested and the cycle is repeated.
5.1. Impact of exotic species
 Introductions are movements beyond the present geographical range of a species and are intended
to insert totally new taxa into flora and fauna.
 Species are introduced beyond their geographical range for the purpose of aquaculture; ornamental
fish trade, enhance genetic characteristics or re-establish a species that has totally failed.
 About 168 species from 37 families have been reported to be introduced world over. Out of these,
67 species have established themselves in the new environment and 7 species have become pests.
 A few of the important species that were introduced into India are the Chinese carps namely silver
carp, grass carp and common carp. They are used in composite fish culture along with the Indian

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major carps catla, rohu and mrigal. The Chinese carps were also introduced into the reservoirs to
enhance fish production.
 Tilapia was also introduced into natural water bodies, where it has completely established itself.
 The illegal introduction into India was the African catfish.
 Clarias gariepinnus which is a highly predatory has a serious potential to destroy native species. It
has already established in many parts of India and is presumably causing extensive harm to the
native species.
 The Thai catfish Pangsiodan hypothalamus has recently been introduced to India to augment fish
production.
 Apart from these the mosquito fish Gambusia affinis was introduced to control mosquito larvae –
the adult mosquitoes spread the malaria parasite Plasmodium
 Many ornamental fish have been introduced all over the world away from their natural habitat.
5.2. Adverse impacts of Introductions
When introduced, species escape from the farm; or, when they are deliberately introduced into natural
ecosystems such as lakes, reservoirs and streams, they have potential to cause adverse impacts on the
ecosystem and biodiversity into which they are introduced. A few of the following adverse impacts are
listed below:
 Depletion of biodiversity
 Endangering native species
 Compete for food and space with native species.
 Introduce new parasites and diseases
 Genetically interact with local species and contaminate the gene pool of the native species.
 Degrade ecosystems
 Have adverse impacts on the socio – economic aspects of human life.
The introduced species will have more adverse impact on the freshwater because; although freshwaters
represent only 0.1% of the earth’s water it contains 40% of the total fishes on the earth. Out of these, 20%
of the fauna is already extinct or are at the verge of extinction. Introduction will further aggregate the
situation and may lead to extinction of more species.
Case study -1
In Lake Victoria of Africa there were about 300 endemic species of fish. 99% of the population (8 million
people) of Kenya, Uganda and Tanzania depended on Lake Victoria for their lively hoods and food.
The Nile perch Lates niloticus was introduced into this lake with the intention of enhancing fish
production. Majority of the endemic fish became extinct, affecting the livelihood of the 8 million
populations.
Case study - 2
Introductions within the country into a different habitat can also cause severe adverse effects on the local
flora and fauna. Grass carp a native of China was introduced to Danghulake in China. It resulted in
complete destruction of macrophytes leading to plankton blooms. Big head carp and silver carp, also
natives of China were introduced to control the resulting algal blooms. Algal blooms were not completely
controlled, but the number of benthic species came down to 26 from the original 113 and zooplankton from
203 to 71. The drinking water supply was completely affected.
5.3. The way forward
The introductions of non-natives into a new region must be considered with great caution. Once in a new
location the ecology of the ecosystems must be closely monitored. Care must be taken not just with the
species concerned but also with the associated organisms, which may be accidentally introduced with it.

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There should be strict quarantine of the species indented for introduction before they are introduced in
aquaculture facilities.
The escapements should be contained by the following measures.
 Regular inspection of the pond walls – sluice gates and farm effluent outlets.
 The ponds should have secondary back-up containment facilities.
 Predator deterrence should be followed
 Underwater predatory netting around net cages should be provided
 Site surveys, prior to farm construction covering flood frequency, height above water table etc.,
should be undertaken
 All in-farm fish handling operations to be conducted within continued area.
Introduction can be both harmful and beneficial. Care should be taken to avoid possible adverse effects of
introduction of exotic species.
Sewage Fed Fish Culture
6.1. Introduction
Fish production in ponds fertilized with waste water is a common practice in some parts of Asia. Sewage
fed fish culture is now well established since it is perceived to be more attractive than intensive farming.
The systems include fish culture technology and sanitation engineering – it can result in substantial energy
saving also.
Waste fed aquaculture dates back to more than a century in Germany where ponds receive effluents from
other biological treatment systems. Net fish production from waste fed aquaculture is Germany averages
500 kg/ha/7 months, with loading rates equivalent to waster water generated by 2000 persons/ ha/yr.
Munich with 233 ha designed to treat waste water from 500,000 people produces a gross fish yield of 100 –
150 mt./yr. The main fish species used are common carp (Cyprinus carpio) and tench (Tinca tinca). The
German system was designed to operate in temperate regions and thus yields are low due to low stocking
densities than the tropical waste fed aquaculture systems.
The concept of using aquaculture as a tool for waste water treatment has been evaluated through a
systematic research programme carried out over a 5 year period by the CIFA, Bhubaneshwar. In
collaboration with the Public Health Engineering Department, Govt. of Orissa, the Indian Aquaculture
Sewage Treatment Plant was designed comprising of duckweed and fish culture. Three species of Indian
major carps and three species of exotic carps were stocked in treated water. Production levels of 3-4 metric
tons/ha/yr were realized.
In spite of the development of the Aquaculture Sewage Treatment plant, West Bengal, the only state in
India where sewage fed fish culture is practiced, uses raw sewage for fish culture.
Fish is grown in Bheries using raw sewage from Kolkata city in about 10,000 ha area.
6.2. Sewage and its characteristics
The term sewage is used loosely to include the combined liquid waste discharges of domestic and
Industrial sources within a given area. It is a cloudy liquid having minerals and organic matter in solution,
colloidal form and solids floating as suspension.
It contains about 90-99% water. It also contains bacteria and protozoa. It is rich in phosphorus (1-14 mg/l)
and nitrogen (18-120%). It contains traces of heavy metals such as zinc, copper, chromium, Manganese,
nickel and lead. The BOD and COD of the sewage are very high. The direct use of raw sewage is
detrimental to fish because of its high BOD, low DO, High CO2, high levels of ammonia, hydrogen

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sulphide and bacterial and organic load.
Problems related to sewage fed culture system
 Accumulation of silt and high organic matter at the pond bottom.
 Incidence of parasites and fish diseases.
 Possibilities of pathogens being transferred to humans.
 Accumulation of heavy metals in the system.
Solutions
 Regulation of treated sewage intake into ponds
 Dilution with freshwater and use of prophylactics.
 Depuration of fish in freshwater before marketing.
6.3. Use ofraw sewage for fish culture
The raw sewage needs to be treated before using in fish ponds.
Mechanical, chemical and biological treatments are the three steps involved in treatment of raw sewage.
Mechanical Treatment
This step is required to remove suspended and floating solids from the raw sewage. The solids are removed first by
using screens and then by skimming. Finally they are removed by sedimentation.
Chemical treatment
Chemical treatment of raw sewage involves steps such as coagulation/chemical precipitation, deodorization,
disinfection and sterilization.
Biological treatment
Sewage is treated biologically by using natural bacterial activity for the oxidation of organic matter.
The treated sewage can than be used for fish culture after suitable dilution with freshwater.
6.4. Sewage fed fish culture of West Bengal
 As stated earlier, West Bengal is the only state in India where raw sewage is used for fish culture.
 The sewage fed fish culture is carried out in Bheries where raw sewage from Kolkata city is let into
the Berries in small quantities at monthly intervals.
 In small Bheries fish and paddy are grown alternately while in bigger Bheries only fish is grown.
The sewage is let into the ponds to a depth of 90 cm along with tidal water in a ratio of 1:4, sewage
to water. The water is allowed to settle for 15-20 days after which it becomes clear and odourless.
Subsequently plankton will grow in the Bheries. The ponds are then stocked with fingerlings of
Indian major carps of size 7.5 – 15 cm in the month of April. Some farmers also stock silver carp
and common carp. Harvesting begins in September and ends in February. The weight of the stocked
fish is about 500-550 kg/ha and the final yield from this system is about 3000 kg/ha/year.
 Tilapia can also be grown in sewage fed ponds since they are capable of tolerating poor water
quality prevalent in sewage fed ponds and production of up to 9000 kg/ha/yr of 70-200 mm Tilapia
can be obtained.
 Raw sewage has the potential to cause human health hazard. Therefore only treated sewage should
be used for fish culture.
 Other countries such as Far East, Middle East, Germany, Hungary and Israel use treated sewage for
fish culture.

24
Cultivable carps
Catla catla (catla)
 It has a large conspicuous head with a deep body
 Snout is broad
 Mouth large upturned
 Lips without fringes
 Females mature at age of 2 years; males at 1- 1½ years
 It is a surface feeder feeding predominantly on zooplankton
 Catla is the fastest growing among IMCs
 Grows to 1-2 kg in a year
 Grows to over 1.5 m in length over its age.
 Breeds naturally in the rivers of North India during rainy season
 Widely distributed in India, Pakistan, Bangladesh and Myanmar
 Has been transplanted to the south Indian rivers
 Seed production through induced breeding.
Labeo rohita (rohu)
 Small pointed head, with elongated body
 Moderately convex abdomen
 Mouth terminal with fringed lips
 Matures at the end of two years
 Column feeder feeds predominantly on phytoplankton and filamentous algae
 Breeding and distribution similar to catla
 Grows to 750-900 g in a year; growth faster second years onwards
 Grows to over 0.9 m.
Cirrhinus mrigala (mrigal)
 Small head, blunt snout and elongated body
 Mouth sub-terminal, lips without fringes
 Body silvery, dark grey on back, fins orange, tinted with black
 Bottom feeder, feeds mainly on detritus
 Grows to about 700 g in 1 year
 Breeding and distribution similar to catla and rohu
Labeo calbasu (kalbasu)
 Small head with subterminal mouth
 Fringed lips, small scales
 4 barbels present
 Body bluish green
 Bottom feeder/omnivore
 Attains max. Length of 1 m
 Common in Indian rivers and occasionally in brackish waters

25
Hyophthalmichthys molitrix (silver carp)
 Body compressed with small head
 Mouth sub-superior with lower jaw upturned
 Eyes comparatively small, situated below the horizontal body axis
 Colour of the body silvery white; dorsal brown
 Surface feeder feeding on phytoplankton
 Attains 1.5 to 2 kg in 1st year
 Max size 60 cm.
Cetnopharygodon idella (grass carp)
 Large sized, cylindrical body with a flat head
 Abdomen round scales larger
 Lower jaw shorter and eyes small
 Feeds on aquatic plants, terrestrial grass
 Feeds up to 5 times its weight per day
 Grows up to 10 kg in one year
 Max size 1.5 m/30 kg.
Cyprinus carpio (common carp)
 Body compressed with round abdomen
 Mouth slightly downturned with blunt snout
 2 pairs of barbels on upper jaw; lower pair slightly longer
 Long dorsal fin, scales thick, and big
 Omnivore; bottom feeder
 Grows to 1 – 1.5 kg in one year
 Breeds freely in ponds
Varities of common carp
 Scale carp – C. carpio communis
 Mirror carp – C. carpio specularis
 Leather carp – C. carpio nudes.
Cultivable air breathing fish
Clarias batrachus (magur)
 Dorsal and anal fin long
 Pectoral fin with long serrated spine
 Head dorso-ventrally compressed
 Body round
 Widely distributed throughout the country
 Max size – 46 cm
 Attains maturity in one year
 Feeds on fish, organic debris and worms (omnivore)
 Breeds during monsoon in paddy fields, swamps and marshy areas
 Deposits eggs in a nest made in the form of depression

26
 Exhibits parental care
Heteropneustis fossilis (Singhi)
 Dorsal profile almost straight
 4 pairs of barbels, head depressed
 Dorsal fin short and spineless. Pectoral spine strong, osseous and pointed
 Feeds on insect larvae, fish and worms
Channa marulius (Giant murrel)
 Body cylindrical, compresses posteriorly
 Head depressed
 Cleft of the mouth extends beyond the eye
 Hardy species, can withstand acidic waters
 Breeding season April to June
 Largest of the Indian murrels
 Max size 1.2 m, grows to 50 – 70 cm in a year
 Highly predatory, even cannibalistic
 Suitable for culture in swamps
Channa straitus (striped murrel)
 Lower jaw longer, cleft of mouth oblique
 Maxilla extends beyond the posterior margin of the eye
 Feeds on small fishes
 Breeds in ponds, throughout the year with peak in monsoon season
 Max size recorded 90 cm
Aorichthys seenghala (giant river catfish)
 Body elongate and compressed
 Long flattened chisel shaped snout
 4 pairs of barbels, maxillary pair reaching no further than pelvic fins
 Found in Indian rivers and in neighboring countries
 Grows up to 1.8 m
 Predatory, feeds on small insects and gastropods
 Breeds during April to May
Aorichthys aor
 Snout round, 4 pairs of barbells, maxillary pair reach the base of the caudal and beyond
 Found in lakes, reservoirs and estuaries of India
 Predatory feeds on other fish
 Breeds during April to May
 Makes nests with pebbles in river beds
Wallago attu (Freshwater shark)
 Body elongate and laterally compressed
 Large head

27
 Mouth reaches beyond eye
 Small eyes, lower jaw longer
 2 pairs of barbells, longest maxillary barbel reaches beyond the front end of the continous anal fin
 Highly predatory
 Breeds during rainy season
Ompak bimaculatus (butter catfish)
 Body elongated laterally compressed
 Short head
 Mouth gape small
 4 barbells, mandibular pair reaching pelvic fin
 Dorsal fin short anal fin long and continuous
 Caudal deeply forked with pointed short lobes
 Distributed throughout India
 Grows up to 30 cm
 Breeds during monsoon
 Considered tasty fish in N.E states of India
Weed fish and predatory fish
Introduction
 Undesirable in culture systems
 Small in size and uneconomical
 Compete with food, space and DO with cultivable species
 Spawn in summer and proliferate becoming abundant in monsoon
 Have high fecundity and hardy
 Need to be eradicated to enhance production of desirable species
Weed fish mostly belong to orders cypriniformes and cyprinodontiformes
Cypriniformes
 Family Cyprinidae
o Puntius sp
o Rasbora daniconius
o Garra lamta
o Danio equipinnatus
 Family: Anabantidae
o Macropodus sp.
Order: Cyprinodontiformes
 Aplocheilus lineatus
 Ambasis sp.

28
Species
Puntius mahicola
 Barbels present
 A dark band along dorsal fin
 Deep black oval mark present at the base of the caudal fin
Osteobrama sp.
 Lower jaw shorter
 Barbels absent
 4-6 narrow vertical bands on the body.
Danio aequipinnatus
 Lower caudal lobe larger
 Several blue vertical bands and several longitudinal bands present
Rasbora daniconius
 A black band runs from eye to base of caudal fin.
 Lower jaw slightly prominent
Garra sp.
 Mouth inferior
 Longitudinal bands present on the body
Applocheilus lineatus
 White blotch on upper surface of head
 Mouth superior
 Irregular bands on body
 Feeds on mosquito larvae
Eradication of weed fish
Weed and predatory fish can be eradicated by use of toxins of plant origin or by the use of chemicals. Use
of pesticides is not recommended since they are not environment friendly. Teh following material can be
used to eradicate weed and predatory fish.
Toxins of plant origin
 Mahua oil cake: applied @ 200-250 ppm
 Derris root powder applied @1-10 ppm
 Jaggery @1%

29
Chemicals
 Bleaching powder @175 kg + Urea 100 kg. Per hectare
Work-out
 Calculate the amount of mahua oil cake to be applied @ 250 ppm to eradicate weed fish in the
following culture systems
 Pond 20m x 50 m, depth 1.5 m
 Well: radius 25 m depth 10 m
 Tank: 0.5 ha.
Aquatic insects
Introduction
 Insects are the most diverse and successful group of animals
 Nearly 80% of the world fauna are insects
 Quite a large number of insects spend at least part of their life in water
 11 orders inhabit water – out of these only beetles and bugs spend their whole life in water
 They are dependent on atmospheric air for respiration
 Hence, more prevalent in shallow waters
 They are generally desirable on fish ponds since they are important part of the aquatic food web
 However, in nursery ponds they are undesirable, since they feed on spawn and fry.
 They also compete with spawn for food and space.
Major aquatic orders
 Hemiptera
 Coleoptera
 Odonata
Minor orders
 Ephemeroptera
 Trichoptera
 Lepidoptera
 Diptera
Species
Gyrinus sp.
 Order coleoptera
 Commonly called whilrgig beetle
 Bluish black in colour
 Antenna short, middle and hind legs flattened
 Feeds on vegetable and animal matter
 Harmful to fry
Dytiscus sp.

30
 Great diving beetle
 Grows to 2.5 cm
 Legs fringed with hair-like structures
 Hind legs flattened
 Feeds on spawn and fry
Hydrophilus sp.
 Silver beetle
 Feeds on spawn and fry
 Carries water droplets at the top of hind legs which appear as silver globules
Notonecta sp.
 Ord. Hemiptera
 Body slightly cylindrical
 Anterior pair of legs leathery at the base
 Hind legs flattened and fringed for swimming
 Found in large numbers in ponds fertilized with organic manure
 Feeds on spawn and small fry
 Common name back-swimmer
Corixa sp
 Ord.Hemiptera
 Dorso-ventrally flattened body
 Tail end blunt
 Forelegs have flat structures
 Body dark greenish in colour marked with dark spots
 Harmful to spawn and fry
 Commonly called water boatman
Gerris sp
 Ord. Hemiptera
 Common name pond skater
 Longer and thinner legs
 Body thin
 Skates on water film
 Not so predatory
Spharodema (water bug)
 Body flat with sucking beak
 Colour brownish to green
 Produces toxic salivary substances which helps to kill fish

31
Lethoceros sp.
 Giant water bug
 Not so common in culture ponds
 Body flat, oval; brown or dull green
 Forelegs smaller, others long and ciliated
 Highly predatory, feeds on spawn fry and even fingerlings
Ranatra sp. (water stick insect)
 Body much elongated
 Legs long and slender
 Breathing tube long
 First pair of legs used for holding prey
Nepa sp.
 Water scorpion
 Body oval, prothorax broad
 Long spine like structure at the tail which act as breathing tube
Dragon fly nymphs
 Order odonata
 2 types: short bodied and long bodied
 Found crawling at the bottom of the pond
 Small projections at tail region with mechanism to close and open
 Expulsion of air through pores helps them to propel in water
 Feed on spawn and fry
Study of aquatic weeds
Introduction
 Weed infestation is a problem in aquaculture, particularly in earthen ponds
 Control is easier in small ponds but not in large ponds
 Adds substantially to operational cost
Growth of weeds depends on
 Depth of water
 Type of bottom sediments
 Fertility and clarity of water
 Climatic condition
Disadvantages of weeds
 Hinder navigation
 Increase sedimentation
 Decrease plankton production
 Harbour predatory and weed fish
 Harbour insects

32
 Water loss through transpiration
 Hinder netting operation
Advantages of weeds
 Increase DO
 Reduce CO2
 Egg collectors – Common carp, gold fish etc.
 Food for some fish
 Ornamental in aquaria
 Control of excess algal blooms
Classification of weeds
Weeds are classified based on the area in which they are present in ponds as follows
 Floating weeds: Unattached free floating, leave above surface and roots dangling down
 Submerged: Completely submerged in water, rooted at the bottom, some without roots
 Emergent: rooted at the bottom, all or some part of the leaves above water
 Marginal: found on the shore line rooted in water logged areas
 Filamentous algae: form mats or scums in pond
Floating weeds
Eichhornia sp.
 Exotic, introduced from Brazil
 Multiplies rapidly
 Present in stagnant water bodies and slow moving rivers
 Leaves broad, swollen at the base of the leaf stock, filled with air – aides in floating
 Flowers purplish pink
 On plant can give rise to 1000-1200 in 4 months
 Forms fodder
 Used for breeding gold fish and common carp
Salvinia sp.
 Ranks second among problematic weeds in India.
 Exotic, introduced from Africa
 High infestation, especially in Kerala
 Stem a delicate floating rhizome, branched and dorsally covered with oblong semi-spherical leaves
 Leaves sessile with or without stock
 Leaves arranged in three whorls- two lateral floating and third submerged
 Submerged leaves covered with minute hair-like structures
 Leave have pimple like swellings which aid in floating
 Multiplies very rapidly through spores and vegetative propagation
Azolla sp.
 Leaves lobed, scale like, thick and about 0.r5 mm long. They have no rudimentary leaves.
 Young, plants green in colour, turn brown when they become old
 Commonly found in stagnant water bodies and paddy fields

33
 Good food for grass carp
 Fixes nitrogen
 Reproduction vegetative
Pistia sp.
 Ranks third among floating weeds problem in India
 Tufts of leaves rise in a form of rosette at the ended of the short stem
 Has number of branching rudimentary roots
 Leaves sessile, arranged in closed spiral, forming the shape of a cup
 Multiplies by vegetative propagation
 Common in Orissa and West Bengal
 Can be biologically controlled by giant gouramy
 20 gouramies control 1 ha Pistia in one month.
Submerged Weeds
Hydrilla
 Stem slender, grows up to 0.5 m in length
 Can infest water even 12m in depth
 Common in India
 Leaves are linear
 Flowers during October to January
 Grows fast
 Reproduces by vegetative propagation
 One of the important ornamental plant
 Causes problems in fish ponds
 Grass carp feeds on this weed
Vallisnaria sp.
 Rooted to pond bottom.
 Leaves are linear and ribbon like and have sheath at the base.
 Grows up to 30 – 35 cm in length and 5-7 cm in width
 Dark green in colour
 Flowers during Oct. to March
 Ornamental
Ceratopyllum
 Perennial submerged rootless plant
 Sometime anchored to bottom by shoot
 Leaves finely divided and located in whorls at the nodes
 Grows up to 20cm in length
 Flowers from Jan to March

34
Cabomba sp.
 Submerged rooted plant with leaves placed opposite to each other.
 Structures looking like fans
 Stem slender with gelatinous line
 Good ornamental plant
Chara sp.
 Plant with whorls of short branches
 Attached to soil by rhizoids
 Flowers soft, encrusted with calcium deposits in hard waters
 Musk like smell when crushed
Nitella sp.
 Stem cylindrical
 Leaves arranged as Whorls at regular intervals
Myriophyllum
 Long and slender stem
 Pinnate leaves in whorls of 4-6
 Highly segmented
 Masses of stems detach and float
Emergent weeds
Nymphea sp. (Water Lilly)
 Found in still water bodies
 Leaves leathery, 10-20 cm in dia. Oval to round with deep slit in the margin.
 Leaves float with main veins radiating from the centre
 Solitary flowers, white, pink or purple in colour
Nuphar (yellow Lilly)
 Leaves round and heart shaped.
 Petiole attached to the lower end of the leaf
 Veins radiate from the midrib, running to near margins without forking
 Flower yellow
 Found in waters 2 m deep and in slow moving freshwaters
Nelumbo (lotus)
 Perennial, found in stagnant waters
 Leaves raised about water surface
 Diameter 60-90cm
 Leaf margins upturned
 Petiole attached to middle of each blade
 Large flowers pinkish red in colour

35
Nymphoides (fringed water lilly)
 Leaves round, float on the surface
 Petiole attached to lower end of leaves
 Veins branch and re-curve to unite with each other
 Flowers small, white or yellow
 Generally each plant with a single leave.
Marginal weeds
Typha sp.
 Found in slow moving streams and margins of lakes and river banks
 Perennial, robust, 2-4 m tall plant
 Stem without nodes, spongy, arising from subterraneous rhizomes
 Leave long, flat, linear, soft
 Spikes 15-30 cm long, drumstick like
Cyperus
 Triangular stems
 Leaves arise in rosette from stem base.
 Prominent inflorescence that has simple of compound flowers
Scirpus
 Perennial marginal weed found in shoreline marshes
 Usually soft leaves, small, clasped to stem base
Marsilia quadrifolia
 Small fern of shallow waters
 50-100cm long stolon
 4 flower-like leaflets placed on tip of a slender stalk.
 Common in ponds and paddy fields
Collocasia sp.
 Common marginal weed found in groups or rows along the margin of ponds.
 Leaves ovate, 6-20 inches in length and 3-12 inches wide
 Apex rounded, leaf margins dark green
 Petiole 3-4 feet long and green, violet or purple in colour
 Has tuberous rhizome
 Shoots and leaves eaten in certain areas

Freshwater aquaculture 2nd sem (full syllabus)

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