Aquaculture Systems

AQUA CULTURE SYSTEMS

The process of Culture of aquatic
organisms is called Aquaculture.  Depending on the   nature   of water used for the aquaculture basically,
it is of three types: Fresh Water aquaculture, Mari Culture and
Brackish Water aquaculture.   Basing
on various aspects like, the availability of soil, space, water, use  of supplementary feed, water exchange, human
resources, and suitable environmental conditions different aqua culture systems
are in practice. 

Knowledge of relative growth, maturation
and fecundity of aquatic animals   is
necessary before planning aquaculture. 
Growth of the fishes depends on the population density and availability
of food.  Attainment of sexual maturity
also depends on the abundance of food and duration of feeding.  Temperature, 
photoperiod and several other factors influence maturation of
gonads.  Fecundity means number of eggs
contained in the ovary. 

 1.7.1.         Types of
Aquaculture based on the use of supplementary feed and the extent of water
exchange     :

1.7.1 .1:  Traditional system of aquaculture:

           This is the oldest system of aquaculture; in this
system supplementary feed is not used similarly there is no water exchange from
beginning to the end.   Fish cultured in
this system fed with the natural plankton available in the pond.

1.7.1.2: 
Extensive system of aquaculture:

            This is the
first developed system of aquaculture. In this system supplementary feed is
given to the fish or prawn grown in pond at large intervals of one week or 15
days. Use of manures and exchange of water is very limited.

          1.7.1.3: Semi
intensive system of aquaculture:

This is the scientifically developed
system. 2% supplementary feed per kg organisms will be given daily. Exchange of
water is regulated at regular intervals.

1.7.1.4: Intensive system of aquaculture:

           This is highly
developed and scientific method of culture system. Supplementary feed is given
at regular intervals. Water exchange will be carried out accordingly.  Supplementary feed will be given at the rate
of 5- 8 %. Optimum environmental conditions are maintained to obtain maximum
yield.

1.7.1.5: Super intensive system of aquaculture:

This is the advanced and
scientifically improved system. In this system culture will be carried out in
the cement lined ponds or cement cisternae or pvc tanks. 100 % water exchange
will be done at regular intervals. Use of supplementary feed and nutrients is
more in this system.

Generally prawn culture is carried
out by the above extensive, intensive, semi intensive, and super intensive
systems of aquaculture.

1.7.2:
 Types of aquaculture systems depending on the
species cultured in the pond.

          1.7.2 .1: Mono  Culture:

Monoculture, as
the name implies, is the culture of a single species of an organism in a
culture system, in any type of water, fresh, brackish or salt. Feeding with
species specific feed is the main basis for monoculture. 

In this type of culture system only
one species is cultured in the pond. e.g.
Culture of Catla catla (common Carp)     in
fresh water ponds.  Culture of  Penaeus monodon in brackish
water culture.

e.g., Catla Catla.  This species
has the fastest rate of growth among the Indian major carps. Stocking density
of hatchlings in stocking pond  is
10,00,000 to 12,50,000 per hectare. Stocking density of finger lings in the
rearing pond is 5,000 to 10,000.

1.7.2.2:
Poly culture or Composite culture :

Composite fish culture is the most significant development of
the country in freshwater aquaculture, during which period, the evolution of
multispecies fish culture technology in stocking ponds took place.

The main aim of fish culture is to achieve the highest possible
fish production from ponds and water resources. The techniques of fish
cultivation involve both management of soil, water and husbandry of fish. Two
criteria, less consumption of water by fish and high fecundity, go very much in
favour of fish cultivation. Fish provide high quality food rich in protein,
vitamins and other nutrients necessary for human health and growth.   The fish pond is a complex ecosystem. The
surface is occupied  by floating
organisms like phytoplankton and zooplankton. The column  region has live and dead organic matter sunk
from the surface and the  bottom is
enriched with detritus or dead organic matter. The marginal areas have a
variety of aquatic vegetation. The different tropic levels of a pond are
utilized for increasing the profitability of fish culture. In view of this a
recent concept in fish culture has been formulated called composite fish
culture. It is also known as polyculture. 
The main objective of this intensive fish culture is to select and grow
competable species of fish of different feeding habits to exploit all the types
of available food in the different regions or niches of the fish pond to get
maximum fish production.

At each trophic  level in
the food chain, considerable amount  of
the original energy is lost from the system. Hence, efficient fish  culture aims at making the chain as short as
possible. Thus, herbivorous fishes are preferred along with zooplankton feeding
fish. It is always  better to exclude
carnivorous fishes from the system.  Usually
a mixture of plankton and macrophyte feeders are stocked in fish culture
systems. They utilize the nutrients, which are already found in the ponds or applied
from outside. If the proper balance is not maintained they do not grow at the
same pace and one group dominates over the other, often utilizing most of the
nutrients and leaving litter for the other. To maintain a balance, stocking is
done with a mixture of fishes of different feeding habits. Ungrazed phytoplankton
is fed upon by the zooplankton, and to utilize them the fish which feed on this
zooplankton are included in the combination. The best combination in India in a
polyculture system is rohu, catla, mrigal, common carp, silver carp and grass
carp. Their feeding habits are entirely different; they never compete with each
other and are not predatory fishes. Rohu is a column feeder and utilizes the
plankton of that area only. Catla is a surface feeder and feeds on only
Zooplankton. Mrigal is bottom feeder and feed on the plankton which is
available at the bottom, mostly benthos. 
Common carp is also bottom feeder, but eats the detritus only. Silver
carp is a surface feeder, but feeds only on phytoplankton. Grass carp feed only
on aquatic vegetation. That means they utilize most of the food organisms
present in the pond. The combination of the phytoplankton-feeding silver carp,
the zooplankton-feeding big head and the weed-eating grass carp is most common
in China and South- East Asia.

1.7.2.3.
Superiority
over the monoculture

Monoculture is the culture of a single species of fish in a
pond.  If only one species is introduced
into a pond, due to the same dietary habits, all the fish congregate at one
place. Naturally, when monoculture is preferred, more number of fish of one
species are introduced.  This  results in high competition for food and
space. Due to the fights, heavy mortality of fish will occur. Because
insufficient amount of food, the fish will not grow to good size and the yield
is affected. In monoculture systems other niches are vacant and in that area
and the available food  in these niches
remains wasted.

Composite fish culture is undoubtedly more superior over  monoculture. In composite fish culture, the
above problems will not be  found. Six
varieties of fishes utilize food of all niches of the pond, get  good amount of food, grow well without any
competition and the yield  is also very
high. The mortality rate in composite fish culture is  negligible. In monoculture a yield of about
500/kg/ha/yr is difficult,  but in
polyculture system the yield is about 20 times more than that of  monoculture with scientific management

 1.7.2.4. Principles
of composite fish culture:

The scientific based technology of composite fish culture aims  at maximum utilization of the pond’s
productivity. Fast growing, non predatory, non-competable species of food
fishes are cultured together  with
complementary feeding habits and capable of utilizing both the  natural and supplementary fish food. At the
same time one fish is useful  to the
other. For example the excreta of grass carp is useful for growing  fish food organisms, on which other fishes
feed. The fishes never face  any
competition for space and food. Bottom feeders like common carp  and mrigal subsist partly on the faecal
matter of grass carp. If the bottom  feeders
are absent in a culture pond the excessive faecal matter of the  grass carp may pollute the water. Stocking
optimum number of each productive potential or carrying capacity of the pond
can be increased  by stimulating natural
fish food production through fertilization and 
the use of supplementary feed to provide adequate food for the large  number of fish stocked.

 1.7.2.5. Fishes
used in composite fish culture

All over the world, the major cultivable fishes, especially for polyculture
belong to the carp family. There are three major systems of  carp culture in the world. These are:

1.   Chinese system :- The
Chinese carps are cultured together. These 
are silver carp - Hypophthalamichthys molitrix, grass carp -  Ctenopharyngodon idella and common
carp - Cyprinus carpio.  These are
also called as exotic fishes in India.

2.   Indian system :- The
Indian carps are cultured together and are 
also cultured with Chinese carps. These carps are rohu – Labeo  rohita, catla - Catla catla and
mrigal - Crirrhina mrigala.

3. European system :-
The main species cultured is the common  carp
- Cyprinus carpio.  Other Chinese
carps used for composite fish culture are : bighead carp - Aristichthys
nobilis, mud carp - Cirrhinus molitorella and  black carp - Mylopharyngodon piceus.

The predatory catfish and murrels can also be incorporated in  the composite fish culture system. However,
catfish and murrels should  be stocked
only after the carp species have grown to a considerable  size. The trash fish and the young of common
carp if any, in the culture pond would serve as a good source of food for
catfish and murrels.  The fringe-lipped
carp and the milk fish are commonly cultured 
in the composite fish culture in brackish water culture system. The
airbreathing  fishes like murrels,
catfishes and koi are also cultured together 
in the freshwater culture system.

1.7.2.6.
Stocking
densities and stocking ratio

Generally fish production increases with the increase in the  number of fish stocked per unit area to a
maximum and then starts  decreasing.
There is always an optimum stocking rate in a particular  situation, which gives the highest production
and largest fish. Under  crowded
condition at a higher stocking density fish may compete  severely for food and thus suffer stress due
to aggressive interaction.  Fishes under
stress eat less and grow slowly. By increasing the stocking  density beyond the optimum rate the total
demand for oxygen increases  with obvious
dangers, but no increase of the total yield of the fish is  obtained. Stocking density and stocking ratio
of fishes should be on the  basis of the
quantity of water and the amount of oxygen production.  The above six varieties of Indian and Chinese
major carps should be  stocked at a rate
of 5000 fingerlings of 75-100 mm size/ha. The 
percentage of stocking of the above fishes can be as follows:

Catla and silver carp - 30 - 35 %

Rohu - 15 - 20 %

Mrigal and common carp - 45 %

Grass carp - 5 - 10 %

In the 5 - species
combination excluding grass carp, the optimal 
stocking ratios are catla 6(30%) : rohu 3(15%) : mrigal 5(25%) : common  carp 4(20%) : silver carp 2(10%).  In a 4 - species combination excluding silver
carp and grass carp,  the optimal
stocking ratios are - catla 6(30%) : rohu 3 (15%) : mrigal  6(30%) : common carp 5(25%).  In a 3 - species combination excluding exotic
carps, the optimal  ratios are - catla 4
(40%) : rohu 3 (30%) : mrigal 3 (30%).  An
8 - species combination is also possible for composite fish  culture, where milk fish and fringe-lipped
carps are included in the  culture system
along with Indian and Chinese major carps. But the  growth of the additions is not satisfactory.
The milk fish is a brackish  water fish.
Usually the stocking ratio is catla 2 : rohu 2 : mrigal 4 :  common carp 3 : silver carp 5 : grass carp 2
: fringe-lipped carp 1 : milk fish 1.

1.7.2.7.
Feeding:

With the increase in the carrying capacity of the pond either by
aeration of water, fish growth can be augmented further with the addition  of supplementary feed. For getting very high
production, fishes are fed  with protein
- rich feed. Usually the conversion coefficient is 1 : 2 i.e.  2Kg of feed is given for every 1Kg of fish
yield. With supplementary  feeds such as
rice bran and oilcake, the fishes grow 10 times more.  Detailed information is given in the chapter
on supplementary feeding.  The Grass carp
are normally fed tender aquatic weeds, like Najas,Hydrilla, Ceratophyllum and
Chara, forage grasses or chopped green 
cattle foders like Napier grass, Barseem, maize leaves, etc and kitchen  vegetable refuse. The cattle fodder is grown
on the terraced embankment  of the pond
and fed to the grass carp. They are fed twice at the rate of  100 Kg/ha in the first month and the quantum
is increased by 100Kg/month at fortnightly or monthly intervals, till the end
of harvesting.  The food of grass carp is
normally placed on a floating frame made of bamboo poles.

1.7.2.8.
Harvesting and yield:

Harvesting of fish is generally advocated after one year of
rearing.  Shorter rearing periods may
also be resorted to depending on the pond 
conditions and size preference in the local markets. An individual fish  grows to the size of 0.8-1Kg in 12 months.
Grass carp have a faster  growth rate and
attains a size of 3Kg weight in and year. It contributes  to about 30% of the total fish production of
a pond. Recent results in  Pune,
indicated a new record in fish production through composite fish  culture. The production obtained was 10, 194
Kg/ha/yr in a 0.31 ha

pond with 8000
fingerlings per hectare. An average production of  5000Kg/ha/yr can easily be obtained from the
culture system. This  clearly indicates
the potentiality of fish production through composite  fish culture. 
Trial netting is done once a month to check the growth of the  fish. It also helps in timely detection of
parasitic infection if any. Netting  also
helps in raking the pond bottom which results in the release of  obnoxious gases from the pond bottom as well
as release of nutrients  from the bottom
soil.  In an experiment on polyculture of
brackish water fishes like  Chanos
chanos, Mugil cephalus, Etroplus suratensis and Liza parsia a  production of 2189Kg/ha/yr was obtained. The
combination of Chanos  and Mugil
showed the highest production. Chanos showed the best  growth followed by Mugil.

1.7.2.9.
Problems:

Biological hazards arise from the existence of weeds, predatory  fishes, insects and snakes in the culture
ponds. These problems can be  controlled
if sufficient measures are taken before stocking fishes in  between successive cultures.  Aquatic weeds, if any found in the pond, can
be very effectively  controlled by the
introduction of weed eating fishes like grass carp and  Puntius species. The common predatory
fishes Mystus, Ompok, Wallago, Notopterus, Oreochromis, Gobius, etc. and
weedy fishes,  Salmostoma, Esomus,
Barbus, Ambasis, Rasbora, Amblypharyngodon, etc., are found in the ponds
and compete with fingerlings of carps.  These
should be eradicated during the preparation of the pond. Aquatic  insects such as beetles, Cybister, Stemolopus;
bugs, Belostoma, Anisops and dragon fly nymphs, etc. should be eradicated.  Others like snakes also cause considerable
damage to the fish  crops by feeding on
fingerlings. Molluscs in large numbers always affect  the fish adversely. They can be controlled by
stocking the fish,  Pangasius
pangasius in the pond. They feed on molluscs and reduce  their infestation.

1.7.2.3.Mixed
culture:

          In this culture system both fish and prawn were grown
in a pond.

e.g.,
Culture of Catla and Macrobrachium.

Stocking density  prawn seedlings  15000 to 20000 per hectare along with
the  finger lings of fishes 5000-7000  per hectare . Highest yield  achieved with the stocking density of 1500 –
3000 of finger lings only.  Excreta of
fish will become the feed of the prawn dwelling at the bottom of the pond.   After five months of culture period
harvesting will be carried.

1.7.3.  Pond
Culture:

          In
this culture system a pond is prepared for the culture of aquatic
organisms.  Depending on the type of
water used for the culture it is of the following types:

1.7.3.1: Static freshwater ponds

Ordinary fresh
water fish culture ponds are still-water ponds. They are of different types
based on the water spread area and depth. Some are seasonal and some perennial.
The ponds may get water from the rains, or may have inlet and outlet systems.
The water supply may be from a stream or a canal or from an underground source
such as wells, borewells  etc. The water holding
capacity of the ponds depends on soil composition of the pond bottom and
subsoil water level. The natural biological productivity of such ponds depends
on soil and water qualities. Agriculture ponds are usually small and shallow.
Commercial freshwater ponds have to have an assured water supply and inlet and
drainage systems. In organised aquaculture, the carrying capacity of
still-water ponds is enhanced by manuring  or fertilizing and exercising water quality
control. Fish are also fed from an extraneous source for obtaining fast growth.

Science of
freshwater pond fish-culture has made great strides in recent years and there
is a fast advancing frontier of knowledge on every aspect of pond culture starting
from farm designing and construction up to production of marketable fish of a
wide variety of cultured fresh water species of finfish and shellfish.

Example: carp
culture systems in India.

1.7.3 .2:  Brackish water ponds:

Brackish water
available within the  area of estuaries,
where the rivers confluence with the sea. The pond or the farm is which located
on a tidal creek or stream and there is a system of inlets to control the
ingress and egress of water into and from the ponds.

Examples are: Peaneus monodon culture in coastal
Andhra Pradesh.

1.7.3.3:   Mariculture:

Mariculture is
aquaculture in the saltwater of the sea. It may be in seas, bays, etc.  Cages are built in the sea for the culture of
marine fishes. 

e.g. Latis calcarifer (Sea bass) Culture in
Tamilanadu & Kerala. Seaweed culture.

1.7.4 . Running water culture:

  
 Where there is abundant supply of
water, common carp is cultured in running water ponds. The most intensive
common carp is cultured in running water ponds. In the running water there is
plentiful supply of high dissolved oxygen content and optimum range of
temperature for feeding. Running water culture of common carp is done in the
streams of Krishna and Godavari Rivers Generally these running waters are
called as Vagulu in telugu.

1.7.5. Culture
in recirculation systems:

This system is
comparable to running water culture system except that in the latter, water
goes waste whereas here the same water is reused. In this system, water is
filtered continuously and recirculated, often after aeration, to the fish pond.
The filtering element is a biological filter comprising 3 – 4 cm diameter
pebbles, or honey-comb synthetic strips, designed to arrest faecal matter and
to denitrify catabolic wastes through bacterial action.  This system has been tried experimentally for
carp fry rearing at the Central Inland Fisheries Research Institute,
Barrackpore (W.B) India, with commendable results.  

These systems
are mostly applicable to sophisticated and intense aquaculture.  The cost of feeds is the main operating costs
when using the system.

Fig. 
Recirculation System of aqua culture.

Recirculation
system is of two types:

i.             
Open type : In this type artificial
ponds  dug with dykes in the open area.   

ii.            
Closed type: In this system the entire
system constructed under single roof where the culture units are made of fiber   or
cement.   

1.7.6.   Culture in waste water  :

          Waste water is the water
discharged from domestic and industrial sources within the area.  Waste water is  considered to be good fertilizer for ponds..

          In 1925 for the first time in India waste
water    used
for the culture of fish in West Bengal.  At
present in West Bengal around 6000 hectares culture is under the waste water ,
with an annual production of 1300 kg/hectare. Similarly in Tamilnadu  the 
annual production is 1000-6000 kg/hectare.

Depending
on the composition waste water  is categorized
into the following types: 

1.7.6.1.  Sewage:  Sewage is the liquid 
waste discharged from domestic and industrial sources within the area.  It consists of partially decomposing organic
compounds and salts. It consists of rich composition of plankton. 

1.7.6.2. Silage:
It is the waste water from the  laundries
and washing of clothes. In our country  2960
MGD (million gallon  per day) silage is
produced from the domestic usage.

1.7.6.3. Sludge:
The solid waste settled at the bottom of the water bodies is sludge.  By the biological oxygenation the sludge be
made as activated sludge, which can be used as manure in the aquaculture and agriculture
also.

     1.7.6.4. 
Composition of the sewage:

Sewage consists of the following:

Dissolved Oxygen                      :        Nil

Dissolved Carbon dioxide           :        20.96
ppm

H₂S                                          :        2.4-4.48 ppm.

Alkalinity                                   :        170-490
ppm.

Free Ammonia                          :        12.0-63.6
ppm.    

Nitrite                                       :        0-0.08 ppm.

Phospate                                  :        0.01
– 0.33 ppm.

Suspended matter                     :        160-420 ppm.

pH                                            :        6.9-7.3

       1.7.6.5. Treatment of waste water:

          Waste water is utilized for aqua
culture after the proper treatment. Treatment is by three methods:

          a)
Mechanical treatment: Solids and organic matter
are removed to a large extent by

mechanical treatment, which involves flowing, dilution and  sedimentation. Usually screening and
straining of sewage it is done to  remove
the waste solids. The liquid and semisolid wastes are then subjected to
treatment for the removal of colloidal and semisolid  suspension by dilution, H2S, CO2, CO, NH3,
CH3 concentrations are

brought below the normal levels. Thus, through primary treatment
the  supernatent effluent is separated
from the sludge

          b)
Chemical treatment: In chemical treatment,
several dissolved substances, harmful  germs
and aggressive odours are eliminated. Inexpensive precipitants coagulants,
chelating substances, disinfectants, deodorising agents, etc.  are used in this treatment. The sewage water
is also treated with chlorine,  bleaching
powder and copper sulphate. It is also known as secondary  treatment.

          c)
Biological treatment: In biological treatment
of sewage care is taken to promote 
bacterial growth. Bacterial action promotes oxidation of organic
matter.  The end products nitrogen
oxides, bring about rapid growth of algae, 
particularly the blue green Microcystis. This arrests anoxia of water
by  raising the dissolved oxygen,
lowering the CO2 content and by increasing 
the pH from acidic to alkaline levels. The algal bloom reduces the  concentration of dissolved salts in the
sewage water.

1.7.6.6.
Mechanism of 
treatment of waste water:

          By adopting the following mechanisms waste water treatment  carried out at various stages

1. Pretreatment of waste water :  In the
   pretreatment process the waste materials present in the water are
   eliminated by different techniques like (1) sedimentation; (2) screening;
   (3) shocking to kill aquatic life; (4) filtration; (5) sterilization; (6)
   aeration; (7) degassing (nitrogen, CO₂ removal) (8)
   heating or cooling if necessary (9) pH control. With the above process and
   employing the  biological sieves and
   chemicals and manures pretreatment of water carried out.


2. Dilution of waste water : In this type of pretreatment the water is
   diluted to reduce the obnoxious content concentrations. For that purpose a
   makeup tank with  fresh water is
   maintained.  


3. No treatment of waste water: Some recirculation systems directly uses the
   water once used in the culture. In this type of culture the water reused
   and at the time of reuse water is purified and enriched with nutrients by
   employing biofilters and fertilizers.

4.Post-treatment processes are: Post treatment of water are:              (1) aeration; (2) sedimentation;
(3) filtration; (4) disinfection; (5) activated sludge; (6) lagooning; (7)
digestion or equivalent; (8) coagulation; (9) absorption taste or odors removal
by activated carbon. The post treatment processes enriches the water quality
for the aquaculture.

     Tilapia, Clarius, Heteropneustes  are most suitable species for culture in waste
water.

1.7.6.7. Benefits:

1. Increase
   in fish yields through increase in natural fish food. 


2. Direct
   use of solid organic matter in natural waters by phytoplankton and
   zooplankton.

1.7.6.8. Restraints:

1. Dissolved
   Oxygen  level in ponds.


2. Toxic
   material in wastewater.


3. Tastes
   and odour of  fish.


4. Parasites
   and diseases.


5. Public
   health problems.


6. Pond
   effluent standards.

1.7.6.9.
Site
selection and construction of sewage-fed fish farm

Fish farm in the
vicinity of an urbanized area has the scope to receive domestic sewage for the
recycling of nutrients. Any area adjacent to a municipal sewage treatment plant
is ideal for the location of a  sewage-fed
fish farm. The fish farm site should be at a lower level than  the treatment plant so that the sewage can
easily enter into the pond  through a
pipeline by gravity. The fish farm should have facilities of draining out water
from the ponds.  The plan of the fish
farm depends upon the source of the sewage, 
system of culture and topography of the land. Nearly 75% of the
total  area is converted into ponds
leaving the rest for dykes and other purposes. 
Rectangular fish ponds of 0.3 to 1 ha are constructed with a slope of
1:3 for the embankment and maximum depth of 1.5m. Each pond should have proper
drainage facilities.  The effluent is
collected in a sump at the farm, from where the effluent is taken into the
ponds through the distributing system. 
Additional arrangement is made to connect the pipelines with fresh water  supply for emergency dilution.

Design
for sewage-fed fisheries and irrigation at

Vidyadhari-Kulti
sewage complex Calcutta

1.7.7. Culture in Paddy
Fields:

Rice is the dominant cereal crop in Asia.
It is the staple food of over 1.6 billion people in the  world, mostly in Asia where 90% of all rice
is grown and eaten. For most rural farmers, this single crop is virtually their
sole livelihood. The practice of collecting wild, naturally occurring fish for
food from rice field is probably as old as rice cultivation itself. Fish
culture  in rice fields was introduced
into southeast Asia from India about 1,500 years ago. The problems of food
supplies during the second World War gave an impetus for extensive fish culture
in rice fields.

Paddy - cum - fish culture is a promising venture and if best
management inputs are given it can bring good returns to the growers.  The system works well in paddy fields fed sufficiently
by rivers or lakes.  India has a
traditional system of paddy - cum - fish culture largely practiced in the
coastal states of Kerala and West Bengal. However, paddy - cum - fish culture
in freshwater paddy fields has not been popular although considerable potentiality
exists in India. In India, though six 
million hectares are under rice cultivation only 0.03 percent of this
is  now used for rice - fish culture. The
reason for this is largely attributed to the change in the cultivation practice
of paddy from traditional methods to the more advanced methods involving high
yielding varieties and progressive use of pesticides. Multiple cropping further
improved the returns from such agricultural land, thus shifting the emphasis
from  such integrated farming.  This integrated culture needs abundant water
and low lying areas  are most suitable.
Many million hectares of water spread are most convenient for integrated
culture. In this system two crops of paddy 
and one crop of fish can be cultured in an year.  Water-logged paddy fields are the ideal
natural habitat of various types of fish. Fish in the paddy fields result in an
increased yield of  grain varying from 5
- 15 percent. Fish consume large quantities of weed, worms, insects, larvae and
algae, which are either directly or indirectly injurious to paddy. Fish also
assist in making fertilizing material more readily available to paddy.

Various
techniques are employed for fish culture in paddy fields depending upon the
climate, local conditions, species of fish available and the variety of paddy
cultivated.  The cultivation of paddy is
the primary purpose of the farmer, hence fish culture is to be adapted to the
schedule of paddy cultivation. Species that are suitable for culture in paddy
fields must be able to thrive in shallow water. They should be able to tolerate
high temperature and turbidity.

In certain areas
of West Bengal and Kerala states of our country Paddy field culture system
exists.   Paddy fields remain flooded
with water for a period of 3-8 months in a year, during this period culture of
fish is possible this process is called the Paddy cum fish Culture.

1.7.7.1. Site selection:

About 80 cm rainfall is optimum for this integrated system. Fields
having an almost uniform contour and high water retention capacity are
preferred. Groundwater table and drainage system are important factors to be
taken into consideration for selection of site. 
Suppose the area of the integrated system is 100 m X 100 m i.e., 1 ha.
The area to be utilized for paddy should be 82 m x 82 m i.e., 0.67 ha. The area
to be utilized for fish culture should be 6m x 352 m  i.e., 0.21 ha (4 sides). The embankment area
should measure 3m x 388 m - 0.12 ha. and the area for fruit plants should be 1m
x 388 m - i.e., 0.04 ha. This is an ideal ratio for preparation of an
integrated system. 

1.7.7.2. Rice varieties used
for integrated system:

The most promising deep water varieties chosen for different states
are PLA-2 (Andhra Pradesh), IB-1, IB-2 , AR-1, 353-146 (Assam) , BR-14, Jisurya                (Punjab), AR 61-25B, PTB-16 (Kerala),
TNR-1, TNR (Tamil nadu),  Jalamagan
(Uttar Pradesh), Jaladhi-1, Jaladhi-2 (West Bengal) and Thoddabi (Manipur).
Manoharsali rice variety seeds are used in rice fields where the fishes are
reared.  The paddy plot should be made
ready by April - May. Having prepared the plot, deep water variety of paddy is
selected for direct sowing in low lying areas after the first shower of monsoon
rain.

1.7.7.3. Fertilization
schedule:

The paddy plots are enriched with farm yard manure or compost at
30 t / ha on a basal dose. The nutrient uptake of deep water paddy being very
high, the rate of inorganic fertilizer recommended are nitrogen and potassium
at 60 kg/ha. Nitrogen and posphorus are to be applied in three phases viz., at
planting, tilling and flowering initiation.

1.7.7.4. Pesticide use:

Paddy - cum - fish culture is not developed much due to the use
of pesticides in rice fields for the eradication of different pest and these
are toxic to fish. To overcome the pesticide problem, the integrated pest
control system may be introduced and pesticides less toxic to fish may be used
in low doses, if absolutely necessary. Pesticides like carbomates and selective
organophosptes only should be used.  Furadon
when used 7 days prior to fish stocking proved to be safe.

During the Kharif crop period, pesticides should be avoided.  Harvesting of Kharif crop takes place in
November - December. The yield in this crop is 800 - 1200 kg/ha.  During the Rabi crop, the pesticides can be
used according to the necessity. Before adding pesticides to paddy, the dyke of
the trench should be increased so that the pesticide may not enter into the
trenches.  The yield in this rice crop is
4000 - 5000 kg/ha.

1.7.7.5. Culturable species of fish in rice fields:

 The fish species which  could be cultured in rice fields must be
capable of tolerating shallow  water
(>15 cm depth ), high temperature (up to 350 C), low dissolved  oxygen and high turbidity. Species such as Labeo
rohita, Catla catla, Oreochromis mossambicus, Anabas testudineus, Clarias
batrachus, Clarias macrocephalus, Channa striatus, Channa punctatus, Channa  marulius, Heteropneustes fossilis, Chanos
chanos, Lates calcarifer and Mugil sp have been widely cultured in rice
fields. The minor carps such  as Labeo
bata, Labeo calbasu, Puntius japanicus, P.sarana, etc. can  also be cultured in paddy fields. Culture of
freshwater prawn Macrobrachium
rosenbergii could be undertaken in the rice fields. The  selection of species depends mainly on the
depth and duration of water  in the paddy
field and also the nature of paddy varieties used.

1.7.7.6  Major systems of paddy - cum - fish
culture:

Two major systems of
paddy-cum-fish culture may be undertaken 
in the freshwater areas:

1. Paddy-cum-carp
culture

2. Paddy-cum-air
breathing fish culture

  1. Paddy-cum-carp
culture: Major
or minor carps are cultured in paddy  fields.
In the month of July when rain water starts accumulating in the  paddy plot and the depth of water in the
water way becomes sufficient,  the fishes
are stocked at the rate of 4000 - 6000 / ha . Species ratio may  be 25% surface feeders, preferably catla, 30%
column feeding, rohu  and 45% bottom
feeders mrigal or common carp.

  2. Paddy-cum-air
breathing fish culture: Air breathing cat fish like 
singhi and magur are cultured in paddy fields in most rice grown areas.  The water logged condition in paddy fields is
very conducive for these  fast growing
air breathing cat fish. Equal number of magur and singhi  fingerlings are to be stocked at one fish/m2.
Channa species are also good for this integrated system.

1.7.7.7  Rotational culture of rice and fish:

In this system fish
and rice are cultivated alternately. The rice 
field is converted into a temporary fish pond after the harvest. This  practice is favoured over the simultaneous
culture practice as it permits  the use
of insecticides and herbicides for rice production. A greater  water depth up to 60 cm can be maintained
throughout the fish culture  period.  One or two weeks after rice harvest, the
field is prepared for fish  culture. The
stocking densities of fry or fingerlings for this practice could be 20,000/ha
and 6,000/ha respectively. Fish yield could exceed  the income from rice in the rotational
culture

1.7.7.8 Advantages of paddy - cum -fish culture:

Paddy - cum - Fish
culture has several advantages such as 

1. Economical
utilization of land

2. Little extra labour
is required

3. Saving on labour
cost towards weeding and supplemental feeding

4. Enhanced rice yield
by 5 -15 %, which is due to the indirect organic fertilization through the fish
excreta

5. Production of fish
from paddy field

6. Additional income
and diversified harvest such as fish and rice from  water and onion, bean and sweet potato
through cultivation on bunds

7. Fish control of
unwanted filamentous algae which may otherwise 
compete for the nutrients

8. Tilapia and common
carp control the unwanted aquatic weeds which 
may otherwise reduce rice yield up to 50 %

9. Insect pests of
rice like stem borers are controlled by fish feeding on  them mainly by murrels and catfishes

10. Fish feed on the
aquatic intermediate host such as malaria causing  mosquito larvae, thereby controlling
water-bom diseases of human  beings 

11. Rice fields may
also serve as fish nursaries to grow fry into 
fingerlings. The fingerlings, if and when produced in large  quantities, may either be sold or stocked in
production ponds for  obtaining better
fish yield under composite fish culture.

Considering these
advantages, it is imperative to expand fish 
culture in the rice fields of our country.

Fig: Paddy cum
fish culture.

Paddy fileds to
be used for fish culture are provided with strong barrier wall to prevent
leakage of water, and to convert the field into pond of desire depth. The field
is also provided with trenches or ditches for the fish.  These trenches are connected with a small
pond near the field to provide shelter to the fish against heat. Inlet and
outlet of the field are provided with  screens.

1.7.7.9 Design for paddy cum fish culture:

Three types of
deigns are feasible in the Paddy cum fish culture system they are:     1. Perimeter trench design.

          2. Central trench design.

          3. Lateral trench deisgn.

1.7.7.9.1 Perimeter Trench design :  In this type of pond
trenches dug  at the perimeter. Beside
the paddy field dyke the trench exists. The central part of the field is a
litter higher  than trench, slope of the
field    is towards the trenches, this
condition helps the water to flow into the trench.

1.7.7.9.2 Central trench design:  In this type the trench of
the paddy filed is located in the center of the paddy filed. Surrounding the
trench paddy culture exists. The trench may be in rectangular or square shaped.
The slope of the paddy filed is inclined towards the central trench, thus the
runoff excess water flows into the central trench.  In this system water will be available for
culture as well as paddy harvesting will be available round the year.

1.7.7.9.3
Lateral trench
design:  In this design
trenches for the aquaculture dug on the lateral side of the paddy field.  Slope at 
both ends of the paddy field incline into the trenches on the side of
the field.

.

1.7.8. Cage Culture
system:

          In areas where pond
construction is not possible for aquaculture, in the natural water bodies like
reservoirs, streams, lakes cage culture is in practice. By this culture system
fertile soil used for the construction of pond will be utilized for agriculture
purpose. 

Location of cages:

The ideal location for cages is weed-free shallow waters.
Flowing  water is best for cage culture.
The site should have adequate circulation 
of water. The wind and wave action should be moderate. The water  should be free from pollution and weeds. The
area should be easily   accessible. Cage
culture can also be practiced in areas like swamps where   there is water not being used for any other
purpose. Seed should be   available in
the vicinity. A ready market for fish should be available   near the site. Flowing waters with a slow
current of 1 - 9 m/minute considered ideal for cages. The cages should be a
little away from the  shores to prevent
the poaching and crab menace.

Types of cages

Cages can be circular, cubic and basket like and the shape has  little effect on yield rate. Cages may be
floating at the surface, just   submerged
or made to sit on the bottom. Floating cages may be the   most appropriate for Indian conditions and
the experiments conducted  in our country
for seed rearing, grow out, nutrition and biomonitoring  have been in such enclosures. The size of the
cage depends on the type   of culture
operation and the support facilities available. Large cages are   difficult to handle. Although the cost of
small cages is higher, handling   is easy
with low risk of losses. The nursery cages are generally of the  floating type, while the ground cages may be
floating or immersed   depending on the
species cultured.

Design of cages :

Small cages with mats of locally available plant materials such  as palm leaves. Cyperus stem, Phragmites
stem and split bamboo are  used in
India. These cages are of 1 - 2 m2 area. Split bamboos are joined   with the help of coir rope or nylon twine.
The cages are installed in the  water
body with bamboo supports at the four comers and the bottom.  Materials other than bamboo mats are decayed
by the third month and  collapsed within
a year. Split bamboo cages remain for over a year.  Circular cages with thick bamboo stipes tied
with nylon twine the  durability of over
3 years.   Cages made up of monofilament
woven material of 1 - 3 mm  mesh size and
0.3 - 1 mm thickness are light and easy to handle, but  remain for 6 to 12 months. The exposed part
become brittle and gives  way. Knotless
nylon webbing of 3 - 6 mm mesh size and knotted nylon  webbing of 7 -15 mm mesh have been found to
be most durable. Cages  made of water -
proof surface painted light conduit pipe frames with a  10 m2 area are light in weight and have long
durability. A battery of  cages is
enclosed with a bamboo catwalk and the whole structure floated  by sealed empty barrels of 200 1. capacity.  The circular cages with conduit pipe
structures which can be  easily assembled
have been designed with nylon webbing in different  dimensions. These cages are floated freely on
the water surface with   the help of 3 -
4 sealed HDPP jerry cans. These areextremely useful for  cage culture. Due to their circular is shape
the wave action in minimum.     These can
be moved from place to place with least water resistance. Due to their circular
shape, the rearing space is maximum in side. The  aeration and water circulation is better in
these cages. Fishes can move  in the
cages with least obstruction.  Auto-floating,
highly durable HDPP pipe frame nylon net cages 
with 36 m2 area are also used. These are light in weight and not need  floats to float on the water surface.  The size of the cages depend on die scale of
culture, species  cultured,
infrastructure, financial and management resources. The size  varies from 2- 10m3 in India, 100 - 150m3 in
Indonesia, 60- 180m3 in  Kampuchia. 40 -
625 m3 in Vietnam and 30 m3 in Holland. Large cages  are operated in Germany with 42 m diameter
and 16,500 m3 at the water  depth of 12
m. These are provided with automatic or water jet pumpfeeding,  special handling and harvesting accessories.

Culturable fishes in cages
and their stocking:

T        he fishes used for the cage culture
should be adaptable to captive culture, fast  growing, hardy and disease resistant. The
Indian and Chinese  carps, tilapia and
magur can also be cultured where trash fish is cheaply  and abundantly available. In Thailand and
Kampuchia the cat fishes,   Pangasius species
are being cultured in cages successfully. Koi and  Singhi are also cultured in India in cages.  In India, the nursery cages are stocked with
carp fry at the range  of 150-700 fry/in2
in caaes with different materials. In Japan 15.000-  62.000 fry/nr2 of grass carp fry are stocked
in nursery cages. The   common carp
stocking density is 150/nr2 in Kampuchia, 133 -417/nv1  in Indonesia and 80 - 360/nr2 in Vietnam. In
Thailand Pangasius sutchi,  P. larmmdi
and P. micronemus fry are stocked at densities of 150-300/nr2 in cages of size 1-10 m2 area with a depth of 1.5m.  The number of fish that can be stocked in a cage is variable and  depends on the canying capacity of the water
area, water quality and   rate of
circulation, the fish species, the quality and quantity of feed   supplied. A safe level may be about 3000 to
6000 fish/ ha. In able – fish rearing cages in India, the fingerlings of carps
are stocked at density of  30 - 38no /m2
. The tilapia, Oreochromis mossambicus can be stocked a rate of 100 -
200 m^-2. Murrels can be stocked at density of 40-100m2.

 Management and yield:

The cage culture can be taken up in two phases - nursery phase  and table - fish rearing phase. In nursery
phase of cage culture, the spawn  or fry
are reared to fingerling stage in 2-3 months. Different feeds can  be used for culture in nursery cages.
Groundnut oil cake, rice bran, egg  yolk,
soyabean cake, soyamilk and soya flour are used as food for fry in  nursery cages. The silkworm pupae are also
tried as supplementary food.  The initial
size of fish to be stocked in the cages will depend  primarily on the length of the growing season
and the desired size at  harvest. The
carp fingerlings for stocking in 16-20 mm mesh cages   should be over 10 gr. to expect a final size
of over 500 gr. within 6  months. It
should be ensured that the fingerlings used for stocking are  healthy and disease free. All the fish should
be actively moving. It is   ideal to
stock cages in the cool part of the day.  In India,
the growing season is almost year round, except for   December - January in northern parts, where
the temperature is low  during these
winter months. Very little natural food such as plankton,  insects and various other organisms enter the
cages and is available to  fish. However,
supplementary feeding is essential in the cage culture to  get high production. The types of feed used
will depend on the species   cultured and
their prevailing market prices. Murrels, for example, require  to be fed with fish, shrimps or other animal
matter. Most of the fish  cultured are  mnivorous and they accept both plant and
animal  byproducts such as oilcakes,
brans, fish meal and silk worm pupae.  Cage
fish are generally fed at least once daily throughout the   growing period to get better growth. The
quantity of feed to be given is  important,
since under-feeding will reduce growth and production, while

over-feeding
will waste costly feed and can affect the water quality. A  method used to estimate the daily feed to be
give in cages is based on   the total
weight of the fish. The feed is usually expressed on percentage  of body weight. In carps, the feeding rate is
4 - 5 % of the body weight  per day until
they attain approximately 100 gr. And thereafter at 2 – 3 %.   In table-fish rearing phase, involving the
high-tech system of  saturated stocking
and feeding on enriched formulated feeds, the 
production recorded in common carp is 25 - 35 Kg m° month’1 in foreign  countries. The channel catfish, Lactarius
punctatus in USA yielded a  production
of 20 - 35 Kg/nr3. In Africa, tilapia yielded 17 Kg/nr3and  trout produced 15 Kg/nr3. The food quotient
in these cultures varied  from 1.3 - 2.1.
In India, a production of 1.5 - 2.5 Kg nr: month’1 common  carp was achieved with mixed feed of silk
worm pupae, ground cake  and rice bran.
Catla yielded 1.4 - 2.7 Kg nr2 month’1 with groundnut  cake and rice bran with the food quotient
5.6. Tilapia produced 1 - 1.6  Kg nr2
month’1 with a mixture of rice bran, groundnut cake and  commercial cattle feed and food quotient
ranged from 1.8- 2.3 . About  1 Kg nr2
month”’ of murrel and 0.3 - 1.5 Kg nr2 month’1 of catfishes,  singhi and Koi are obtained.

Cage culture of prawns

The
freshwater and marine prawns are also cultured in cages. The cages are  tocked with wild or hatchery reared post
larvae.  Commercial scale rearing of post
larvae in floating and fixed nursery  cages
(3.7 X 2.7 X 1.3 m) has been done with considerable success.  They are fabricated from fine mesh (0.5 mm)
nylon netting, supported  by bamboo poles
which are driven into the bottom of the water body.  The optimal stocking density reported is
30,000 post larvae/cage (2 .310m’3). Feed is provided in trays fixed inside the
cages. Initially, the post  larvae are
fed on a paste of finely ground trash fish, later are fed with fresh mussel
meat.

             

1.7.8.1 Merits of Cage Culture:

Advanced type of aquaculture having
scores of advantages over pond culture.

1. 10 – 12 times higher yields than pond culture
   for comparable inputs and area.


2. Prevents loss of stock due to flooding;


3. No question of seepage and evaporation losses.


4. No need for water replacement.


5. No problem of pond excavation and dependence
   on soil characterics.


6. Avoids proximity of agricultural areas hence
   reduces hazards of pesticide contamination.


7. Can be conveniently located near urban markets
   avoiding the need for  fish
   preservation and transportation.


8.  Eliminates
   competition with agriculture and other land uses;


9.  Affords
   easy control of fish reproduction.  


10. Complete harvest of fish is effected.


11. Optimum utilization of artificial food.


12. Reduced fish handling.


13. Initial investment relatively small.

1.7.8.2 Limitations of Cage Culture:

1. Difficult to apply when water is rough.


2. High dependence on artificial feeding. High
   quality feed desirable especially in respect of protein, vitamins and
   minerals. Feed losses are possible through cage walls.


3. At times interferes with natural fish
   populations round cage.


4. Risk of theft is increased.

1.7.9.
Integrated culture system:

Integrated culture is defined as  the association of two or more normally
separate farming systems which  become
part of the whole farming system. The major features of this system include:

• Recycling of waste or by-product in which
the waste of one system becomes the input of other system.

• Efficient utilization of farm space for
multiple production.

Integrated livestock-fish, poultry-fish, have
been well developed and practiced in countries like China, Hungary, Germany and
Malaysia. Indian freshwater aquaculture has been largely organic-based, with
inputs derived from activities of agriculture and animal husbandry with plants
and animal residues forming the major component of feeds and fertilizers in
carp polyculture. For centuries, small-scale farmers have sustained themselves
by practising different kinds of crop diversification.  About 80% of India’s population lives in
rural areas at subsistence or near subsistence level.  These rural folk are greatly under-nourished
and need not only a large supplement of animal protein in their diet but also
new sources of gainful employment. India being an agraricultural economy,
produces large quantities of plant and animal residues, 321.4 million metric tonnes
of plant material   and 1000 million metric tonnes of  animal dung on annual basis. It is known that
the country supports the largest bovine population of over 240 million cattle
heads along with 108 million sheep and goats, 7 million pigs, 140 million
poultry and other live stock. Activities like mushroom cultivation and rabbitry,
  apiculture, etc. apart from providing for
diversification of farming systems, also provide huge quantities of organic
material, that may become resources in the 
aquaculture system. The agro-based industries like distilleries and food
processing pants also produce the effluent that could be recycled to
aquaculture apart from the well known 
resource-domestic sewage to the extent of 4000 million liters per day.

Fig:
Integrated system of aquaculture:

1.7.9.1.
ECOSYSTEM OF INTEGRATED FISH FARMING

Integrated fish farming system works in
following way:  Trapping of solar energy
and production of organic matter by primary producers. Utilization of primary
producers by phagotrophs or tertiary consumers.

•     Decomposition
of primary producers and phagotrophs by saprotrophs or                   osmotrophs

   •    Release of nutrients for producers.

  The
animal waste in water body enter into the food chain in three different                                            ways

1.7.9.1.1.
Feed:

Certain
bottom feeders like Cyprinus carpio and
Cirrhinus mrigala directly utilized
the  organic particles which are
generally coated with bacteria along with other material.

1.7.9.1.2.
 Autotrophic
production:

Some
of the decomposed portion of waste products provides nutrients for the
micro-flora  (autotrophs), while
non-mineralised portion provides food base for bacteria and protozoa (heterotrophs).
Temperature, light, micro and macroflora, inorganic nutrients, carbon,  phosphorous and nitrogen are the basic inputs
required for photosynthesis process.

1.7.9.1.3.
Heterotrophic production:

Micro fauna (zooplankton) feed on small
manure particles coated with bacteria. In the 
process, bacteria is digested while rest is excreted. In this heterotrophic
production system  micro fauna
(protozoans and zooplanktons) are produced finally shortening food chain. This  system of production is not linked with the
process of photosynthesis.

1.7.9.2.
DUCK-FISH INTEGRATION:

Duck-fish integration is the most common
integration, mainly practised in China, Hungary,  East Germany, Poland, Russia and upto some
extent in India. It utilises the mutually 
beneficial biological relationship between fish and duck. Asia is
considered to be the holy land of the domesticated ducks, but the best breeds
and strains currently available have been developed for their excellent
egg/meat production in Europe and America through systematic breeding, feeding,
management and disease control.

 Duck
eggs are an important source of food in India. These are very cheap to produce
and can play an important role in balancing the diet of the Indian people.
Consumption as well as production of duck eggs in India is mostly done by socially
weaker sections of the community. The production of duck eggs is about 400
million/year which is 5% of the total egg output in the country.

Fig: Duck fish integrated farming

1.7.9.2.1.
Benefits of duck rearing:

1.
Rearing of ducks is limited to watershed regions. It is very popular among
villagers as a profitable  back-yard
enterprise as average egg production from ducks is higher than local fowls.

2.
They have great foraging capacity.

3.
Maintain egg productivity almost at the same level up to the age of 2 to 3
years as compared to 1 to 1½  years in case
of fowls.

4.
Eggs are bigger and because of thicker and strong shell, transportation is
easier and breakage during transit is lesser.

5.
Energy level is higher in duck eggs than in hen egg.

6.
Ducks feed on a large variety of organisms like snails, flies, earthworms,
insects, etc, Ducks may serve as effective biological control of a number of
human and animal  diseases.

7.
Ducks keep the water clean by controlling potato beetles, grass hoppers and
other aquatic fauna. They feed on green algae and weeds thereby helping in the
control of unwanted plants.

8.
Ducks are quite hardy, easily brooded and resistant to the common diseases.
They need less attention and area easily manageable.

9.
Cannibalism behaviour is not usually encountered in ducks.

10.
Duck eggs are larger than the chicken.

11.
Ducks do not require extensive housing.

12.
Cholesterol level in duck egg is less as compared to the eggs.

1.7.9.2.3.
Varieties of ducks:

Ducks are of several kinds as the egg type,
the meat type and the ornament type. In India, mainly ducks of egg-laying type
are reared.

The
famous Indian duck breeds for eggs are:

(a)
 Sylhat mate

(b)  Nageswari

(c)
 Indian Runner

(d)
Khaki Campbell - Khaki campbell is recommended for integration duck-fish.  As they are prolific layers they can be
reared economically. These ducks start laying eggs  when they are 3 months old. The annual
average egg production is about 300 eggs or more.

1.7.9.2.4.
Housing:

A comfortable house should provide adequate
accommodation, be reasonably cool in summer and 
sufficiently warm during winter. It should be free from draughts and
should at the same time provide adequate supply of fresh air and sunshine and
always remain dry. The house should give adequate protection against sudden
changes and extreme temperatures as these have an adverse effect on the health
of birds. The house should also give protection to the birds from their natural
enemies like jackals, foxes, dogs, cats, rats, snakes, kites and crows. 

Centralised
enclosure - In this method, a relatively large duck shed is constructed
in the vicinity of the fish ponds with a cemented area of dry and wet runs
outside. The average stocking rate is about 4 
ducks/m2. The dry and wet runs must be cleaned daily. During cleaning,
the sluice of the wet run is opened to allow organic manure to be flushed into
fish ponds through a manure ditch. After this, the sluice is closed and the wet
run is filled with fresh water. This method is advantageous for its  centralized management mechanisms, but it is
unable to fully utilise the leftover and undigested duck  feed. It is also unable to take advantage of
the duck-fish symbiosis. 

In
the fish-pond - This is the most common method of
integrated fish-duck farming. The dykes of 
grow-out ponds are partly fenced to form a dry run and part of the water
area of a corner of the pond is  fenced
with used material to form a wet run. The net pen is installed 40-50 cm above
and below the  water surface to save net
material. In this way, fish can enter the wet run for food but cannot escape.  In a large pond, a small island is
constructed at the centre of the pond with feeding facilities.  The number of ducks to be raised in fish
ponds depends on the quantity of excreta per duck, which in  turn depends on the species of duck, the
quality of feed applied, and the method of raising.

1.7.9.2.5.
Care of ducklings :

The brooder house should be kept ready and
be checked 24 hours before arrival of ducklings. Each duckling should be given
a drink by dipping its beak in water. It should be provided dry litter. The
birds need heat for first 8-11 days depending on the weather. It should be
checked regularly to avoid any possible complications.

1.7.9.2.6
. Feeding:

First 3 weeks are vital for future growth
and the ration should be high in protein. There should be balance between
cereals and protein. The starter ration should also contain vitamins, mineral
salts and trace elements. A feed containing 17% protein in a high energy ration
will be enough for proper growth of ducklings. In layer ration 15% protein will
serve the purpose. Ducks are voracious eaters 
and foragers. Apart from compound feeds snails, fingerlings, earthworms,
insects and other vegetative  forms are
taken by them when reared in ponds. It reduces the feed cost. Ducks have
difficulty in  swallowing dry mash.
Pellet feeding is popular which reduces wastage, feed cost and labour cost.  Ducks are very much susceptible to aflatoxin
produced by fungus, Aspergillus flavus,
is groundnut oil  cake. Duck can tolerate
up to 0.03 ppm as against 0.2 ppm in chicken. The mouldy feed toxicosis is  more harmful to the ducklings than adult
ducks.  Annual consumption of feed is
about 50-60 kg per duck. It requires about 3 kg of feed to produce a  dozen eggs and 3.22 kg feed to produce 1 kg
of broiler duck. The layer requires 200-210 grams of  food per day.

1.7.9.2.7.
Benefits of duck-fish integration:

A fish pond is a semi-closed biological
system. In fish ponds, there are many aquatic animals and plants, most of which
are natural food organisms of fish, some are detrimental to fish but can be
utilized by ducks. Fish ponds provide ducks with an excellent, essentially
disease free environment. Ducks consume juvenile frogs, tadpoles, and dragonfly
larvae, thus eradicating many predators of fry and fingerlings. Furthermore,
the protein content of these natural food organisms of duck is high. Therefore,
duck raising in fish ponds reduces the demand for protein in duck feeds. For
ducks raised in pens, the digestible protein content in the feed must be 16-20
percent; for ducks raised in fish ponds, the digestible protein content can  reduce to 13-14 percent. This can save
200-300 g available protein for each duck, equivalent  to 2-3 percent the duck feed. Duck droppings
go directly into the pond, providing C, N, and 
P and stimulating the growth of natural food organisms. This direct
fertilisation of the pond  has two
merits: 1, there is no loss in the availability of manure: 2, direct
fertilization is more  homogeneous and
avoids any heaping of duck droppings. For these reasons, raising ducks on  fish ponds promotes fish growth, increase
fish yields and eliminates pollution problems that might be caused by excreta
in duck pen.  The quality and quantity of
duck excreta, however, are dependent on species, feeds applied,  culturing management, and climatical
conditions. The stocking rate of ducks is generally  300-500 ducks/ha and each duck produces about
7 kg of dropping during the 36 day fattening period. If 500 ducks are raised,
3500 kg of excreta would be produced in that t period. The  moisture content of duck excreta is 56.6
percent; organic substance, 25.2 percent; C, 10 
percent; P2O5, 1.4 percent; N, 1 percent; K2O, 0.62 percent; Ca, 1.8
percent; and others. Each  egg-laying
duck annually produces 7.5-10 kg (dry weight) of excreta (equivalent to 70 kg
wet  weight).

Duck feeds are fully utilised in fish-duck
integration. Ducks lose 10-20 percent (923-30 g/day) of their feed. This feed
can directly be consumed by fish.  Fish-duck
integration also promotes the recycling of nutrients in the pond ecosystem. In  shallow areas, a duck dips its head to the
pond bottom and turns the silt to search for benthos.  By virtue of this digging action, nutritional
elements locked in the pond humus will be 
released. Ducks also act as pond aerators. Their swimming, playing and
chasing disturbs the  surface of the pond
and aerates the water.  Duck raising in
fish ponds has three advantages over raising ducks in pens. The feed  efficiency and body weight of each duck improved.
The higher feed efficiency also implies  than
the waste feeds are utilised by the fish. The food conversion factor in
fish-duck  integration was reduced from
3.84 to 2.64. The survival rate is increased by 3.5 percent  because fish ponds provide a clean
environment for the ducks. It was believed that if fish and  ducks were raised in the same pond, the ducks
would eat the small fish. However, above 5 g 
the fish is able to escape from the duck.

1.7.9.3.
FISH-LIVESTOCK SYSTEM

Fish farming using manure has long been
practised all over the world. Integrating fish and  livestock farming reduces the necessity to  purchase fertilisers and fish feeds, and
increases  the income generated by the
fish farm.

1.7.9.3.1
Management

Animal sheds can be built close to the fish
ponds to simplify the handling of the manure. The  faeces and urine may be collected separately.
If the floor is higher than the pond dyke, a 
manuring ditch can be dug to collect the faeces and urine together and
the mixture can be  flushed directly into
the fish ponds. This method saves time and labour. The area of the fish  pond to be matched with the number livestock
and waste food; the species ratio and target 
output of fish, etc. The frequency of manuring depends on the conversion
of the manure,  which changes seasonally,
and the fluctuation of food organisms in the fish ponds. Cow  faeces and urine are beneficial to filtering
and omnivorous fishes. Therefore, silver carp and catla are usually the major species with assorted omnivorous fish
(common carp) and  herbivorous fish
(15-20 percent). The optimal output of herbivorous in fish-cow integration
should be around 12 percent of the total output of the pond. With more
herbivores, supplement feeds must be applied. 
India does not possess a suitable native breed of pig to develop pig
industry. The common village pig in India is a scrub animal, with its growth
being slow and poor. It produces small litters. The pork produced by this
animal is of poor quality. Several exotic breeds of have been introduced in
India to augment pork production. Amongst these breeds, are the large white
Yorkshire, middle white Yorkshire, Berkshire and Landrace.

1.7.9.3.2
Biological basis:

Among all livestock excreta, cow excreta is
the most abundant and, in terms of availability, the most reliable. A 450 kg
cow annually produces 12000-13000 kg of faeces and 8500-9000  kg of urine. The nutritive content of cow
dung, however, is a little less than of pig excreta. If  0.024 kg of fresh cow manure is applied to 1
m3 of water every day, inorganic N and P will 
be 0.897 and 0.024 mg/l, respectively. These levels are close to the
inorganic N (0.97-2.06mg/l) levels in high-yield fish ponds. The N/P ratio will
be 36.9.  The increase in natural food
organisms, detritus, and bacteria in fish pond enables filter feeding and
omnivorous fish to grow faster. The conversion factor of cow manure is 3.15 in  dry weight or 21 in wet weight at an average
weekly manuring rate of 0.17 kg/m3 in filtering 
and omnivorous fish farming. In silver carp it is 3.3 in dry weight or
26 in wet weight at the same manure input.  Cow manure particles sink at 4.3 cm.min. If
the same amount of manure is applied, after 24 h, the density of suspended
organic detrius below 0.65 μm in the cow-manured pond (40 mg/l), around 150
percent is higher than in pig-manured pond. 

Cow feed mainly on grass and during the
grass-growing season (about 7 months), an adult 
cow requires 9000-11000 kg grass. Around 3000 kg of this grass, however,
is leftover. That  period of time is the
highest ingestion season of herbivorous fish: therefore, this waste  fodder can be utilised as fish feed to the
grass carp. The food conversion factor of terrestrial wild grass is 40-50. In
addition, the matted grass in the cow shed can be used as compost for  the pond. The leftover fine fodder for cows
can also be used as fish feed.  Under
favourable conditions of management, a good sow or gilt can produce two
litters/year  and raise about 7
piglets/litter. The piglets are weaned at the age of 8 weeks. The growing
animals are ready for market at about 6 months of age. The gilts retained for
breeding attain puberty at the age of about 8 months and farrow at about one
year of age. The average duration of pregnancy in pigs is 114 days. The male
piglets which are maintained for stud purpose become fit for service after the
age of 7 months. The ration between the breeding boars and sows in a herd is
usually 1:15.

1.7.9.4.
POULTRY-FISH SYSTEM:

A simple and economically viable system of
fish-cum-poultry farming has been developed. 
Under the system, the poultry droppings of fully built up poultry litter
is recycled in the  polyculture fish
ponds which results in production of 4,500-5000 kg fish. Broiler production  give good and immediate returns to the
farmers.  The most important factor a
farmer should consider before taking up broiler production is to  investigate the market conditions, where the
product will be sold. There should be steady 
demand for his chickens, so that all the stock could be disposed of
immediately when they are  ready for
market. Success in broiler production depends mainly on the efficiency of the  farmer, his experience, aptitude and ability
in the management of the flock. Profitable 
production of broilers requires the following factors:

1.7.9.4.
1.Procurement of  stock:

Broiler chicks should come from fast
growing, well feathering, strain-bred and cross-bred parents to  convert feed into meat efficiently in shorter
time. They should also have resistance to disease and  should have broiler qualities. These chicks
are available mostly at commercial broiler hatcheries, and  they have to be procured by placing orders
with them.

1.7.9.4.
2. Housing:

Efficiency in broiler operation depends on
several factors and facilities. The main is poultry housing.  Prevention of diseases can be accomplished
with good housing. Proper housing reduces mortality and  morbidity losses. The broiler house should be
built where there is goof ventilation and one should be  able to maintain the temperature. Common type
houses should be gable type with open sides. Width  of the houses should not exceed 0.3 metres
(30 feet) in order or effect proper ventilation. Length of the  house is usually left to the convenience of
the farmer depending on the number of broilers raised  giving about 22 to 23 sq. cm. floor space per
bird. Height of the house should be about 3 metres. One  half to two thirds of the house is covered
with wire mesh. Curtains for windows are necessary to  combat extremely cold nights and winter
months.

1.7.9.4.
3.Equipment:

Hovers made of G.I. metal sheet having 4
electric bulb holders or 3 infra-red bulbs may be used for  brooding 250 to 300 chicks. about 30 cm high
cardboard or G.I. sheet chick guard is required.

1.7.9.4.
4.Feeders:

G.I. sheet grill type feeders are durable
for chicks which are easy to clean and reduces feed wastage.  about 8 cm feeding space up to 8 weeks of age
should be provided per bird. Two size of feeders are  recommended chick size and broiler grower
size.

1.7.9.4.
5.Waterers:

Aluminium 2 litre capacity up to 2 weeks of
age for 100 chicks and plastic waterers 4 to 5 litres  capacity up to 8 weeks of age should be
provided. In the beginning a wooden board should be placed below the waterer to
avoid spilling of water into the litter and litter falling into waterers.

1.7.9.4.
6.Management practices:

Brooder house should be thoroughly cleaned,
and disinfected at least 15 days before chicks are  brooded. About 6 to 8 cm dry absorbent litter
(paddy husk or saw dust) be spread on the floor. The  litter should be covered with 2 to 3 fold
newspaper for the first 5 days to prevent chicks eating litter  material when they are hungry. At least 12
hours before the chicks arrival, brooder lights should be put

on
and make sure they are in working condition and required heat is maintained. Use
a chick guard to  keep the chicks
confined to the brooders at least 50 to 60 cm away from the brooders. This may
be  moved away from the brooder gradually
and removed after 8 to 10 days. Few hours before chicks  arrive, waterers and feeders should be filled
and kept ready at equal distance around the brooder so that  the chicks can start drinking and eating
immediately. It is advisable to ensure about 18^oC temperature  for drinking water. Feeders should be kept
full for the first few days.

1.7.9.4.
7.Care of chicks:

1.
Chicks should be taken to the brooder house immediately when they are received.

2.
Chicks are let down under the hover, where there is ample heat and near the
feeders and waterers

3.
During the first few weeks they should be watched carefully to enable them grow
into vogorours, healthy and profitable broilers.

1.7.9.4.
8. Brood House Management:

Brooder temperature should be around 35^oC
at the edge of the hover i.e. 15 cm from the surface of the litter. This
temperature is reduced about 2.5^oC per week until the chicks do not
require artificial heat i.e. up to 22^oC too much heat in the room
may result in poor feathering and cannibalisms. If the room  is too cool chicks will huddle together under
the brooder and will not eat and drink enough to put on  weight. Important thing is to keep the
brooder house temperature around 23^oC to 25^oC by covering  windows with a plastic sheet during winter or
gunny bags during summer months especially during  night. The brooders have to be raised as the
chicks grow and after 5th or 6th week or age they may  gradually be removed.

1.7.9.4.
9. Floor space:

Crowding birds is expensive-death losses
from piling up and disease rise. Enough floor space of about  22 to 25 sq cm. should be made good. In
cooler season 20 to 22 sq cm. space/bird is ideal.

1.7.9.4.
10.Feeder space:

Birds should not fight to get to feeders.
They will eat more when feed is easy to get to. Space the  feeders evenly so that chicks do not walk
more than 20 to 25 cms.

1.7.9.4.
11.Water space:

Broiler chicks need plenty of fresh water
in order to make best use of their feed. Availability of  drinking surface is more critical than amount
of water in waterers. Hence, several small waterers are  better than few large ones. Requirement of
floor, watering and feeding space for different age groups  on deep litter system.

1.7.9.4.12.
Problems in poultry-fish  integrated
culture system:

Poultry-fish association generally yields
very high profit. A comparison of the variable cost  of production of broilers, its farm-gate sale
price and its retail market price show that 
farmer’s profit is quite high. the profit from fish culture is much
higher than from poultry  farming and
requires very little investment capital. The association of both further
reduces  the capital involved in fish
farming and make the system more profitable.  
The turnover and total profits are both very high for such a small farm
and should enable the  farmer to make
adequate saving, for his working capital, considering his cost and standard of  living. To improve the farmer’s living
standard, technical assistance is more important than  financial assistance. This should include
instruction in modern farm management techniques

and
efficient utilisation of farm resources, such as land, labour and capital. Most
of the farms  are relatively small scale
and produce only small quantities of fish, fowl and other  agricultural products mainly for farm-gate
sales or low volume sales at local markets. The 
buyers at the farm-gate are usually local merchants from the area. The
farm-gate prices  fluctuate in relation
to the market prices, but are usually below current market prices by an  amount which depends on the quantity of
produce, its seasonal availability, and the existing  arrangements between farmers and buyers. The
larger farms which produce high quantities seems to have a higher bargaining
power, which is reflected in the higher farm price that they  receive. Large farms, therefore have less
marketing problems than smaller ones.

1.7.10. Pen culture:

Aquaculture in open waters through the use of pens or enclosures  is also a means of minimising the limiting
effect of metabolities and  pollutants on
cultivated stock. Greater production in very limited space  has been found possible under those
situations..

1.7.10.1.  Selection of sites for pen culture

·        
Low tidal amplitude

·        
Fish pen - site must be sheltered as much as possible against
high winds

·        
Depth not less than 1 meter during lowest water level.

·        
The best site is on the leeward side of the prevailing winds
with  moderate flow of current especially
in a place where current in overturning

·        
Water with stable PH slight variation is best. Avoid turbid and  polluted water.

·        
Muddy clay and clay - loam soils are best types of bottom soil.

Too much still and
decomposing organic matter must be avoided.

1.7.10.2 Construction
of pens:

Pens can be
constructed with the help of bamboo screens and 
nets.

1.7.10.2 .1. Construction of pens with bamboo screens:

Split bamboo should
not necessarily be shaped and rounded. They 
are soaked in water for two weeks and then dried for one week. During  the soaking and drying period, bamboo poles
are prepared and staked at  the chosen
site according to thedesired size and shape of the fish pen.  After stacking poles, bamboo splits are
closely woven extending to a  length of
more or less five meters and made into a roll. After weaving,  these are set by stretching them from one
pole to the other interrurned  or just set
inside or outside close to the poles from bottom to top. They

are tied every pole by
rubber and one provided with sliced rubber around,  liming one on top and one at the bottom.
These splitted rubber prevent  them from
wear due to wave action. Nursery nets which should be 1/16  th to 1/10 th of the area of the fish pen can
be set before constructing the  fish pen
or after it is set.

1.7.10.2 .2. Construction of pen with nets:

Construction of a fish
pen made out of synthetic netting is easier 
than one made of bamboo screens. Netting materials can be kuralon,  nylon, cremona, tamsi. etc. An ordinary
fisherman can connect the nets   into the
fish.pen after taking into account the desired height or depth of   the pen site. After the net is constructed ,
the poles are staked in mud  after making
a provision for the front rope and tie rope at the interval of  1.0 - 2.0 m per stake and also the provision
for float rope. In preparing  the poles,
all nodes are cleaned except one node with brunch protruding  one inch which is staked in the mud from 15 -
30 cm or more depending  upon the depth
of soft mud. With this node the foot rope is tied, and  these together with the bottom net are staked
in the mud. Boulders can  be used as
sinkers in the absence of lead sinkers. Bamboo tips of 1-1 mm are also used to stake the bottom
net with a foot rope firm into the  mud
to avoid escape of the fish stock. Construction of the nursery net  may be done before or after the construction
of the fish pen. They should  have a free
board of about 1 meter above the normal water level to  prevent entry or exit of fishes by jumping
and as a precaution against  water level
fluctuations.  Metal and metal coated
with HDPP screens are often used for pens which 
is highly durable. 

1.7.10.2 .3 Supplementary
feeding:

The fish pens that are
densely stocked with 10-20 fish per square 
meter, generally need regular feeding at the rate of 4 -10 % of the
total  body weight of the stock at least
once 3 week, or it could be divided  into
daily feeding. The amount of food to be given depends on the  condition of the culture fish which could be
checked through sampling  at least once a
month.

polyethylene).
Pen wall can be constructed in several pieces each piece having a frame work
consisting of a few rows of horizontal struts, and two vertical struts along
the two sides. Vertical bamboo bracers at intervals of 4 m or more should be
provided depending on the bottom condition, water current, wind velocity etc.

For net pen wall
the mesh size of netting should not be more than 10 mm. HDPE knotless webbing
is best for net pen wall. If material of appropriate height is not available,
sticking of two or more width of material will be required. HDPE rope of 4-5 mm
and 3-4 mm thickness should be tied to the bottom and head line of the net
respectively. Loops at interval of 3-4 m in the foot rope is needed for tying
with bamboo groove which is driven into the mud. This arrangement is to ensure
tucking of about 30 cm of the net into the mud. Steps for installation of the
net pen is more or less similar to bamboo screen fencing. 

1.7.10.2.4. Management of pen:

1) Eradication or removal of aquatic weeds such as water
hyacinth and Hydrilla should be done properly before
installing the pen otherwise the clogging of pen wall might be a serious
problem.

2) Another important aspect which needs
consideration is the presence of predatory fish which could not be totally
eradicated by any known technology or netting. Therefore large sized
fingerlings need to be stocked.

3) Due to the presence of higher
organic matter, species combination may be changed and more bottom dwelling
species like common or mirror carp and mrigal should be introduced.

4) The introduction of Chinese carp
such as grass carp and silver carp is essential since Indian major carp like
rohu, catla, and mrigal do not consume aquatic weeds nor  these fish consume phytoplankton like silver
carp, whereas common carp is essential to rake up the bottom mud to make
available the nutrients present in the bottom.

5) Presence of submerged weed might
sometimes cause serious oxygen depletion. The weed  need to be controlled by introducing grass
carp (Ctenopharyngodon idella).

6) Because of soft bottom, the net wall
should be sufficiently driven into the mud to ensure tucking of at least 30 cm
of the net wall into the mud.

Fig. Pen in a  fresh water lake.

1.7.11. Raft culture:

Rafts are generally made of
bamboo poles or metal rods with  buoys at
the top for floating in the water. These are used in the culture of oysters, mussels
and seaweeds in open seas.

Fig. Raft arranged in the sea

1.7.12. Rack culture:

Racks are constructed in
brackishwater areas and inshore areas  for
rearing oysters, mussels, seaweeds, etc.

Racks are constructed at the
depth of 1-1.25 m depth .  It is a fixed
structure comprising of several wooden poles vertically driven into the
substratum over which a wooden frame is made at a height of 0.5 m above the
water level.

1.7.13. Raceway culture:

A series of earthen or cement
tanks are constructed along the  course
of a river or stream and are used for fish culture. Raceway is a  culture chamber that is generally long and
narrow. Water enters at one  end and
leaves through the other end in most cases.

1.7.14.
Hanging, ‘on bottom’ and stick methods of oyster culture:

In the hanging
method, oysters as they grow, are suspended from rafts, long-lines or racks.  The long-line system has horizontal lines
attached to wooden barrels or metal drums at or near the surface from which
strings of seed oysters are suspended. The long-line system is used in offshore
grounds. The system can withstand rough seas which might destroy rafts.  The structures in the rack method consists of
vertical poles or posts driven into bottom which support horizontal poles. Strings
of seed oyster are tied to horizontal poles such that they do not touch the
bottom. The trend of rack method is downward because of coastal pollution.  In the sowing method, oysters are directly
placed on the bottom.  In the stick
method, seed oysters are attached to wooden sticks riven into bottom in the
intertidal zone. In both stick & “on bottom” method, crawling predators
take a toll of oysters.

1.7.15 .Organic
aquaculture

Sustainability is one of the main goals of
organic food production. quaculturists who aim for  organic farms wish to “manage food production
as an integrated, whole system that is an 
‘organism’ whose individual parts mesh together into one whole
production system. In  organic food
production, all parts of the operations are connected and integrated with each
other,  such as the nutrient inputs, the
animals, the environment, and the wastes being produced.  Organic fish producers must comply with all
of the same regulations that other organic certified  producers do. Some substances or practices
are prohibited from organic operations. For 
example, the addition of antibiotics to the fish feed is tightly
regulated and the inclusion of  genetically
modified organisms is strictly forbidden in organic production. Rather than
rely on  the use of chemicals and drugs
to improve the production of their fish, farmers instead optimize  the living conditions, through lower stocking
densities and cleaner, healthier water. Organic aquaculture standards have been
developed in many nations around the world and they   are in the final stages of development in
the United States. Some of the basic principles of

organic aquaculture
according to the International Federation of Organic Agriculture Movements  are as follows:

·        
To encourage natural biological cycles in
the production of aquatic organisms;

·        
Using feed that is not intended or
appropriate for human consumption;

·        
Using various methods of disease control;

·        
Not  using synthetic fertilizer or other chemicals
in production;

·        
Using polyculture techniques whenever
possible.

There
are several obstacles to the implementation of organic aquaculture,    including:
farming carnivorous fish with a diet of wild (non-organic) fish, management and
recycling of wastes, escapes of fish, and controlling diseases and parasites. Similar
to organic certification, other certification and labeling programs also are under
consideration. These “eco labels”, together with organically farmed seafood,
have great potential   for allowing
consumers to know that the fish they purchase were farmed in environmentally   friendly ways. Additionally, they could
provide responsible farmers with a way to take advantage of the increasing
consumer demand for food grown with environmentally friendly practices as well
as receive a premium price for their product.

Table: Water resources
for aqua culture in India