COMPOSITE AND INTEGRATED FISH FARMING

The basic principle of composite fish culture system is the stocking of various fast-growing, compatible species of fish with complementary feeding habits to utilize efficiently the natural food present at different ecological niches in the pond for maximising fish production. Composite fish culture technology in brief involves the eradication of aquatic weeds and predatory fishes, liming: application of fertilizers on the basis of pond soil and water quality, stocking with 100 mm size fingerlings of Indian major carps-catla, rohu, mrigal, exotic carps, silver carp, grass carp and common carp in judicious combination and density; regular supplementary feeding and harvesting of fish at a suitable time. Composite fish culture system is conducted by adopting three types of combinations viz., culture of Indian major caps alone, culture of exotic carps alone, and culture of Indian and exotic carps together. Fish production ranging between 3,000 to 6,000 Kg. per hectare per year is obtained normally through composite fish culture system. Development of intensive pond management measures have led to increase the fish yield further. Integated fish and animal husbandry systems evolved recently are the fish-cum-duck culture, fish-cum-poultry culture, fish-cum-pig culture, utilization of cattle farm yard wastes and recycling of biogas plant slurry for fish production.

Advantages of the combined culture systems, number of birds/ animals, quantity of manure required and fish production potentiality of the recycling systems are described. Fish culture in paddy fields is an important integrated fish cum agriculture system. Essential requirements of paddy fields to conduct fish culture, characteristic features suitable for culture in rice fields, constraints to culture fish in paddy fields due to recent agrarian practices, and improved fish-paddy farming methodologies are discussed. Freshwater prawn culture is a recent practice. Giant freshwater prawn Macrobrachium rosenbergii and Indian riverine prawn M. malcolmsonii are the two most favoured species for farming purposes in India. Breeding, hatchery management, seed productio, culture systems and production potentialities of the freshwater

prawns are presented. Commercially important air-breathing fishes of India are the murrels, climbing perch, singhi and magur. Techniques of their seed production and culture systems are described.

Composite fish Culture

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.

Population explosion results in the area of cultivable land getting reduced, and consequently, animal protein is likely to be less in future due to limitations of space and food. This indicates that more and more animal proteins will have to be procured from the waters. We have to think as to how to produce more animal protein. The fish is a very good source of protein. We have to consider the production of more fish under controlled conditions in ponds as these offer the greatest potential of all.

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 or mixed farming. 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.

In olden days, the average yield of fish from ponds was as low as 500 kg/ha/yr. This quantity is considered as very poor. In composite fish culture more than 10,000/kg/ha/yr fish yield can be obtained in different agro-climatic regions of our country.

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.

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 kind of fish adequately utilizes the different ecological niches. The 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.

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 : big-head 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 air-breathing fishes like murrels, catfishes and koi are also cultured together in the freshwater culture system.

In India and China, polyculture is more popular unlike in the European countries, where monoculture is still common and prevalent. Due to the fact that seed production of common carp is easier than that of the other cultivable carps, perhaps, it has been the dominant cultivated species throughout the world.

Indian major carps are more riverine in nature and these do not ordinarily breed in confined waters. Hence, their young ones are still collected during the monsoon season from the flooded rivers. Species-wise segregation of natural collection is most difficult, their mixture along with undesirable species are stocked in the ponds. This practice eventually gave rise to the system of polyculture, the scientific basis of which has been realized recently.

During the late fifties exotic carps species, common carp, silver carp and grass carp were introduced in India. These have been successfully cultured together and are now cultured along with Indian major carps. The grass carp in a culture system is essential as it helps in the biological control of aquatic weeds. Grass carp feed voraciously on aquatic vegetation. 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.

At each trophical 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 are fed upon by the zooplankton, and to utilize them the fish which feed on these 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 fee 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.

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.

Management techniques

Pre-stocking management and post-stocking management methods are already discussed in the stocking pond management chapter, 5.

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.

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.

Hazards in composite fish culture

Composite fish farming runs the risk of encountering several incidental hazards, which may cause heavy losses unless they are anticipated and remedial measures taken in time in order to overcome them. Most of the problems emanate because of poor management. Hazards may be either biological or problems of management or harvesting

Biological 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.

Due to the early maturity and natural breeding of the common carp, the rate of these fishes is increased and the stocking density of the culture pond is greatly altered unless some precautionary measures are taken. Hence, common carp may be harvested before they are fully ripe. Otherwise aquatic weeds can be kept in the corners of the pond to lay eggs which are adhesive in nature. The weeds with attached eggs can be removed and the eggs, if so desired, can be incubated separately to obtain hatchlings. By this, the farmers will avoid the breeding of common carp in the pond with less cost and at the same time raise the spwan for sale. Common carp, because of its burrowing nature, can spoil the dyke by making holes in it. Crabs also damage the dyke. Tilapia is a continous breeder, hence it must be avoided in the ponds.

Algal blooms with Microcystis, Euglena, etc. which are found generally in summer months cause serious problems of dissolved oxygen. During day time oxygen is supersaturated and in the night oxygen is depleted. The chemical method is good for eradication of blooms. Pumping of freshwater into the pond at the time of emergency is a safe method. A part of the pond is covered with shady plants like Eichornia and Pistia so as to cut off light. But if they spread in the pond again eradication is a big problem.

The most serious and common hazard is the depletion of oxygen level in the water. The distressed fishes swim at the surface with their snouts protruding above to gulp the air. The growth rate of the fish is seriously affected and often mass mortality occurs. When the fishes come to surface to engulf air, the farmer must aerate the water by pumping freshwater into the pond to save his fish crop. To increase the oxygen content of water, he should beat the water with bamboo poles. Addition of KMnO4 (1ppm) increases the dissolved oxygen content of water and also acts as a disinfectant. Quick-lime or slake-lime at a rate of 200 Kg/ha should also be added to counteract the adverse effect of putrication of organic matter. Repeated drag net facilitates the release of obnoxious gases. Cut banana stem has also beneficial effects on the fish in the above circumstances.

In composite fish culture, excessive growth of plant material is cut down by silver carp and grass carp which subsist on phytoplakton and aquatic weeds respectively. Presence of mrigal and common carp also considerably reduces the adverse effects created by the depletion of oxygen due to the decomposing organic matter since they feed on it. Many ponds in the village are completely shaded by large trees and bamboos, and these interfere seriously with the photosynthetic process in the ponds by cutting down the sunlight. The situation becomes much more serious during windy days and especially during spring when the falling leaves start putrefying in the water.

It is always desirable to avoid trees and bamboos as much as possible onthe margin of the pond. Banana plants can be planted on the dyke, except on the eastern side so that the sunlight is not cut off by these in the morning. Banana plantation should not be allowed to become bushy. The dwarf variety is most suitable for this purpose. Fish diseases is another problem in the culture pond, fish diseases are discussed in detail in chapter-VI,G.

Management problems:

It is always necessary to keep at least 1m of water in the pond. Serious drought severely affects the level of the water in the rain-fed ponds. Alternative sources of water supply like tube-wells could be of some help in fighting against drought. Heavy rain and flood cause serious damage to the ponds by breaking the dykes or over flooding them. In both the cases the fish escape from the pond. Temporary measures such as protection of the dykes or screening of the ponds may be resorted to. Sometimes, it is better to harvest the fish even before such a situation is encountered. Poaching is another problem in fish culture. Besides employing watchmen, bushy plant materials can be introduced into the ponds to prevent easy netting. Trained watch-dogs may prove more effective and economical in controlling poaching.

Harvesting Problems:

It is essential to harvest the fish stock before the rate of growth of the fish for the invested inputs such as feed and fertilizers start declining. The nutritive value of water for feeding the fish cannot be increased after a certain stage. Differential growth complicates the harvesting program, and , it is suggested that, if the harvesting times are very much difficult to synchronize in a community of fish even after careful manipulation of stocking ratio and density, partial harvesting may be resorted to.

The sale prices of fish of less than a Kg is somewhat less as compared to those fish which weigh over a Kg or so. This also influences the harvesting programming, and, to get more profit it is essential to consider this aspect also before harvesting.

Interrelationship of the species cultured is also required to be seriously considered. Bottom feeders subsist partly on faecal matter of grass carp and an unplanned removal of grass carp would, in turn, affect the growth of the bottom feeder, whereas if only bottom feeders are totally harvested the excessive faecal matter of grass carp may pollute the water.

The hazards involved in composite fish culture are manageable and could be effectively averted with by proper precaution and vigil.

Economics

Economics of production of fish in composite fish culture varies from place to place depending on land price, soil condition, cost of labor, cost of farm construction material and transportation. It may not be possible to generalize the nature of fish production and its cost functions. Over all it is highly profitable.

Integrated fish farming

The land-holding of rural people are small and fragmented, and the modern large scale production technologies with high input requirements offer no tangible solution to their problems of low income and low productivity. These small and marginal farmers have livestock in the form of cattle, pigs, a small flock of ducks or chicks, agricultural land and surplus family labour. With these problems and resources, efforts are made to develop low cost farming systems based on the principles of productivity utilization of farm wastes, available resources and man power. The research efforts have resulted in the development of integrated farming systems, involving fish culture, livestock raising and agriculture. The package of practices for integrated farming have been developed and verified extensively for economic viability and feasibility at the farmer’s level.

Fishes can be reared in paddy, wheat and coconut fields. Fruiting, flowering plants and vegetable plants are cultivated on the dykes. Azolla – fish culture is also becoming popular.

Paddy – cum – fish culture

Paddy – cum – fish culture is a promising venture and if best management inputs are given it can bring fancy returns to the growers. The system works well in paddy fields fed copiously 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 exist 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 fertilising material more readily available to paddy.

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.

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.

Types of paddy fields for integrated system:

Preparation of the paddy plot can vary according to the land contours and topography.

1. Perimeter type: The paddy growing area may be placed at the middle with moderate elevation and ground sloping on all sides into perimeter trenches to facilitate easy drainage.

2. Central pond type: Paddy growing area is on the fringe with slopes towards the middle (Fig. 8.1)

Fish cum-paddy indegrated field

3. Lateral trench type:Trenches are prepared on one or both lateral sides of the moderately sloping paddy filed.

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.

Paddy cultivation

1. 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.

2. 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 , at planting, tilling and flowering initiation.

3. 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.

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.

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.

Fish culture in rice fields:

Fish culture in rice fields may be attempted in two ways, viz. simultaneous culture and rotation culture.

Simultaneous culture: Rice and fish are cultivated together in rice plots, and this is known as simultaneous culture. Rice fields of 0.1ha area may be economical. Normally four rice plots of 250 m2 (25 X 10 m) each may be formed in such an area. In each plot, a ditch of 0.75 m width and 0.5 m depth is dug. The dykes enclosing rice plots may be 0.3 m high and 0.3 m wide and strengthened by embedding straw. The ditches serve not only as a refuse when the fish are not foraging among rice plants, but also serve as capture channels in which the fish collect when water level goes down. The water depth of the rice plot may vary from 5 – 25 cm depending on the type of rice and size and species of fish to be cultured.

Five days after transplantation of rice, fish fry are stocked at the rate of 5000/ha or fingerlings at the rate of 2000/ha. The stocking density can be doubled if supplemental feed is given daily. The simultaneous culture has many advantages, which are mentioned under the heading advantages of paddy-cum-fish culture. The simultaneous fish – rice culture may have few limitations, like

1. use of agrochemicals is often not feasible
2. maintaining high water level may not be always possible, considering the size and growth of fish.
3. fish like grass carp may feed on rice seedling, and
4. fish like common carp and tilapia may uproot the rice seedlings. However, these constraints may be overcome through judicious management.

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.

Fish culture:

The weeds are removed manually in trenches or paddy fields. Predatory and weed fishes have to be removed either by netting or by dewatering. Mohua oil cake may be applied at 250 ppm to eradicate the predatory and weed fishes.

After clearing the weeds and predators the fertilizers are to be applied. Cow dung at the rate of 5000 kg/ha, ammonium sulphate at 70 kg/ha and single superphosphate at 50 kg/ha are applied in equal instalments during the rearing period.

Stocking density is different in simultaneous and rotational culture practices, and are also mentioned under the respective headings above. The fishes are provided with supplementary food consisting of rice bran and groundnut oil cake in the ratio 1:1 at 5% body weight of fishes in paddy-cum-carp culture. In paddy-cum-air breathing culture, a mixture of fish meal and rice bran in the ratio 1:2 is provided at the rate of 5% body weight of fishes.

After harvesting paddy when plots get dried up gradually, the fishes take shelter in the water way. Partial harvesting by drag netting starts soon after the Kharif season and fishes that attain maximum size are taken out at fortnightly intervals. At the end of preparation when the water in the waterway is used up for irrigation of the Rabi paddy, the remaining fishes are hand picked. The fish yield varies from 700 -1000 kg/ha in this integrated system. Survival rate of fish is less than 60 %. Survival rate is maximum in renovated paddy plots when compared to fish culture in ordinary paddy plots.

The dykes constructed for this system may be used for growing vegetables and other fruit bearing plants like papaya and banana to generate high returns from this system. The fish can also be cultured along with wheat. This practice is found in Madhya Pradesh.. Like paddy fields, the same fish can also be cultured in wheat fields. The management practices are similar to fish – cum – paddy culture. Fish can also be cultured along with coconut plants.

Fish cum horticulture

Considerable area of an aquaculture farm is available in the form of dykes some of which is used for normal farm activities, the rest remaining fallow round-the -year infested with deep-rooted terrestrial weeds. The menacing growth of these weeds causes inconvenience in routine farm activities besides necessitating recurring expenditure on weed control. This adversely affects the economy of aqua-farming which could be considerably improved through judicious use of dykes for production of vegetables and fish feed. An integrated horti-agri-aquaculture farming approach leads to better management of resources with higher returns.

Several varieties of winter vegetables (cabbage, cauliflower, tomato, brinjal, coriander, turnip, radish, beans, spinach, fenugreek, bottle gourd, potato and onion) and summer vegetables (amaranth, water-bind weed, papaya, okra, bitter gourd, sponge gourd, sweet gourd, ridge gourd, chilly, ginger and turmeric) can be cultivated depending upon the size, shape and condition of the dykes.

Suitable farming practices on pond dykes:

Intensive vegetable cultivation may be carried out on broad dykes (4m and above) on which frequent ploughing and irrigation can be done without damaging the dykes. Ideal dyke management involves utilisation of the middle portion of the dyke covering about two-thirds of the total area for intensive vegetable cultivation and the rest one-third area along the length of the periphery through papaya cultivation keeping sufficient space on either side for netting operations. Intensive cultivation of water-bind weed, Indian spinach, radish, amaranth, okra, sweet gourd, cauliflower, cabbage, spinach, potato, coriander and papaya on pond dyke adopting the practice of multiple cropping with single or mixed crops round the year can yield 65 to 75 that year. Semi-intensive farming can be done on pond dykes (2 to 4 m wide) where frequent ploughing, regular irrigation and deweeding are not possible. Crops of longer duration like beans, ridge gourd, okra, papaya, tomato, brinjal, mustard and chilli are found suitable for such dykes.

Extensive cultivation may be practised on pond dykes (up to 2 m wide) where ploughing and irrigation by mechanical means are not at all possible. Such dykes can be used for cultivation of sponge gourd, sweet gourd, bottle gourd, citrus and papaya after initial cleaning, deweeding and digging small pits along the length of the dykes. Extensive cultivation of ginger and turmeric is suitable for shaded dykes.

Carp production using leafy vegetables and vegetables wastes:

A huge quantity of cabbage, cauliflower, turnip and radish leaves are thrown away during harvest. These can be profitably utilised as supplementary feed for grass carp. During winter, grass carp can be fed with turnip, cabbage and cauliflower leaves, while in summer, amaranth and water-bind weed through fortnightly clipping may be fed as supplementary feed for rearing of grass carp. Monoculture of grass carp, at stocking density of 1000 fish/ha, fed on vegetable leaves alone, fetches an average production of about 2 t/ha/yr. while mixed culture of grass carp along with rohu, catla and mrigal (50:15:20:15) at a density 5000 fish/ha yields an average production of 3 t/ha/yr.

Integrated farming of dairy, piggery and poultry has been traditionally practiced in many parts of the world with a varying degree of success. In India, this system of freshwater fish culture has assumed significance presently in view of its potential role in recycling of organic wastes and integrated rural development. Besides the cattle farm wastes, which have been used traditionally as manure for fish pond, considerable quantities of wastes from poultry, duckery, piggery and sheep farming are available. The later are much richer in nutrients than cattle wastes, and hence smaller quantities would go a long way to increase fish production.

Azolla – aquaculture

The significance of biological nitrogen fixation in aquatic ecosystems has brought out the utility of biofertilization through application of heterocystous blue-green algae and related members. This assumes great importance in view of the increasing costs of chemical fertilisers and associated energy inputs that are becoming scarce as also long-term environmental management. Azolla, a free-floating aquatic fem fixing atmospheric nitrogen through the cyanobacterium, Anabaena azolla, present in its dorsal leaves, is one of the potential nitrogenous biofertilizers. Its high nitrogen-fixing capacity, rapid multiplication as also decomposition rates resulting in quick nutrient release have made it an ideal nutrient input in fanning systems.

Arolla is a hetrosporous fern belonging to the family azollaceae with seven living and twenty extinct species. Based on the morphology of reproductive organs, the living species are grouped into two subgenera. viz., Euazolla (Azolla caroliniana, A.filiculoides, A. microphylla, A.mexicana. A., rubra ) and Rhizosperma (A.pinnata, A.niloiica ). Proliferation of AzollaMs basically through vegetative propagation but sexual reproduction occurs during temporary adverse environmental conditions with the production of both microsporocarp and megasporocarp.

Potentials of Azolla

Though Azolla is capable of absorbing nitrogen from its environment, Anabaena meets the entire nitrogen requirements of Azolla-Anabaena association. The mean daily nitrogen fixing rates of a developed Azolla mat are in the range of 1.02 – 2.6 kg/ ha and a comparison with the process of industrial production of nitrogenous fertilisers would indicate the efficacy of biological nitrogen fixation. While the latter carried out by the enzyme nitrogenase, operates with maximum efficacy at 30°C and 0.1 atm. The fertiliser industry requires reaction of nitrogen and hydrogen to form ammonia at temperature and pressure as high as 300°C and 200 – 1000 atm respectively.

The normal doubling time of Azolla plants is three days and one kilogram of phosphorus applied result in 4 – 5 kilograms of nitrogen through Azolla, i.e., about 1.5 – 2.0 t of fresh biomass. It may be mentioned that Azolla can survive in a wide pH range of 3.5 to 10.0 with an optimum of 4.5 – 7.0 and withstand salinities of up to 10 ppt. With a dry weight range of 4.8 – 7.1 % among different species, the nitrogen and carbon contents are in the ranges of 1.96 – 5.30 % and 41.5 -45.3 % respectively. The percentage ranges of other constituents on dry weight basis are crude protein 13.0 -30.0, crude fat 4.4 – 6.3, cellulose 5.6 -15.2, hemicellulose 9.8 -17.9, lignin 9.3 – 34.8 and ash 9.7 – 23. 8. The ranges of elemental composition are phosphorus 0.10 – 1.59 %, potassium 0.31 – 5.97%, calcium 0.45 – 1.70 %, magnesium 0.22 – 0.66 % and sulphur 0.22 – 0.73%. Added to these are its high rates of decomposition with mean daily loss rates of 1.36 – 4.57% of the initial weight and nitrogen release rate of 1.25% which make Azolla a potential biofertilizer in aquaculture systems.

Cultivation of Azolla

While Azolla is grown either as a green manure before rice transplantation or as a dual crop in agriculture. It is necessary to cultivate Azolla. separately for aquaculture and resort to periodic application in fish ponds. A system suitable for such cultivation, comprises a network of earthen raceways (10.0 X 1.5 X 0.3 m) with facilities for water supply and drainage. The operation in each raceway consists of application of Azolla inoculum (6 kg), phosphatic fertiliser (50 g single superphosphate) and pesticide (carbofuron dip for inoculum at 1 – 2 ppm), maintenance of water depth of 5 – 10 cm and harvesting 18 – 24 kg in a week’s time. The maintenance includes periodic removal of superficial earth layers with organic accumulation, dyke maintenance, application of bleaching powder for crab menace and algal blooms, etc. A unit of 0.1 ha area that can hold about 50 raceways is suitable for a family to be taken up as cottage industry in rural areas. Azolla can be cultured in puddles, drainage and shallow water stretches, at the outlets of ponds and tanks and hence prime agricultural land need not be used. It is advisable to set up central Azolla culture units to serve for the community in the villages.

Applications in fish farming

Azolla is useful in aquaculture practices primarily as a nitrogenous biofertilizer. Its high decomposition rates also make it a suitable substrate for enriching the detritus food chain or for microbial processing such as composting prior to application in ponds.

Further, Azolla can serve as an ingredient of supplementary feeds and as forage for grass carp too. Studies made on Azolla biofertilization have shown that the nutrient requirements of composite carp culture could be met through application Azolla alone at the rate of 40 t/ha/yr providing over 100 kg of nitrogen, 25 kg of phosphorus and 90 kg of potassium in addition to about 1500 kg of organic matter. This amounts to total substitution of chemical fertilisers along with environmental upkeep through organic manuring.

Azolla is a new aquaculture input with high potentials in both fertilisation and tropic enrichment. Studies are also being made with regard to reduction of land requirement and production costs through in situ cultivation in shallow zones or floating platforms in fish ponds, use of organic inputs like biogas slurry, etc. The costs may be reduced further if the Azolla culture system is managed by the farmer or by his household members. The technology would pave the way for economic, eco-friendly and environment conserving fertilisation in aquaculture.

Integrated fish–cum–poultry farming

Much attention is being given for the development of poultry farming in India and with improved scientific management practices, poultry has now become a popular rural enterprise in different states of the country. Apart from eggs and chicken, poultry also yields manure, which has high fertilizer value. The production of poultry dropping in India is estimated to be about 1,300 thousand tons, which is about 390 metric tones of protein. Utilization of this huge resource as manure in aquaculture will definitely afford better conversion than agriculture.

Pond management:

It includes clearance of aquatic weeds, unwanted fishes and insects, which is discussed in detail in the stocking pond management chapter 5.

a. Stocking:

The application of poultry manuring in the pond provides a nutrient base for dense bloom of phytoplankton, particularly nanoplankton which helps in intense zooplankton development. The zooplankton have an additional food source in the form of bacteria which thrive on the organic fraction of the added poultry dung. Thus, indicates the need for stocking phytoplanktophagous and zooplanktophagous fishes in the pond. In addition to phytoplankton and zooplankton, there is a high production of detritus at the pond bottom, which provides the substrate for colonization of micro-organisms and other benthic fauna especially the chironomid larvae. A stocking emphasis, therefore, must be placed on bottom feeders. Another addition will be macro-vegetation feeder grass carp, which, in the absence of macrophytes, can be fed on green cattle fodder grown on the pond embankments. The semi digested excreta of this fish forms the food of bottom feeders.

For exploitation of the above food resources, polyculture of three Indian major carps and three exotic carps is taken up in fish cum poultry ponds. The pond is stocked after the pond water gets properly detoxified. The stocking rates vary from 8000 – 8500 fingerlings/ha and a species ratio of 40 % surface feeders, 20 % of column feeders, 30 % bottom feeders and 10-20 % weedy feeders are preferred for high fish yields. Mixed culture of only Indian major carps can be taken up with a species ratio of 40 % surface, 30 % column and 30 % bottom feeders.

In the northern and north – western states of India, the ponds should be stocked in the month of March and harvested in the month of October – November, due to severe winter, which affect the growth of fishes. In the south, coastal and north – eastern states of India, where the winter season is mild, the ponds should be stocked in June -September months and harvested after rearing the fish for 12 months.

b. Use of poultry litter as manure: The fully built up deep litter removed from the poultry farm is added to fish pond as manure. Two methods are adopted in recycling the poultry manure for fish farming.

1. The poultry droppings from the poultry farms is collected, stored it in suitable places and is applied in the ponds at regular instalments. This is applied to the pond at the rate of 50 Kg/ha/ day every morning after sunrise. The application of litter is deffered on the days when algal bloom appear in the pond. This method of manurial application is controlled.

2. Constructing the poultry housing structure partially covering the fish tank and directly recycling the dropping for fish culture. Direct recycling and excess manure however, cause decomposition and depletion of oxygen leading to fish mortality.

It has been estimated that one ton of deep litter fertilizer is produced by 30-40 birds in a year. As such 500 birds with 450 kg as total live weight may produce wet manure of about 25 Kg/day, which is adequate for a hectare of water area under polyculture. The fully built up deep litter contain 3% nitrogen, 2% phosphate and 2% potash. The built up deep litter is also available in large poultry farms. The farmers who do not have the facilities for keeping poultry birds can purchase poultry litter and apply it in their farms.

Aquatic weeds are provided for the grass carp. Periodical netting is done to check the growth of fish. If the algal blooms are found, those should be controlled in the ponds. Fish health should be checked and treat the diseased fishes.

Poultry husbandry practices:

The egg and chicken production in poultry raising depends upon multifarious factors such as breed, variety and strain of birds, good housing arrangement, blanched feeding, proper health care and other management measures which go a long way in achieving the optimum egg and flesh production.

a. Housing of birds:

In integrated fish-cum-poultry farming the birds are kept under intensive system. The birds are confined to the house entirely. The intensive system is further of two types – cage and deep litter system. The deep litter system is preferred over the cage system due to higher manurial values of the built up deep litter.

In deep litter system 250 birds are kept and the floor is covered with litter. Dry organic material like chopped straw, dry leaves, hay, groundnut shells, broken maize stalk, saw dust , etc. is used to cover the floor upto a depth of about 6 inches. The birds are then kept over this litter and a space of about 0.3 – 0.4 square meter per bird is provided. The litter is regularly stirred for aeration and lime used to keep it dry and hygienic. In about 2 months time it become deep litter, and in about 10 months time it becomes fully built up litter. This can be used as fertilizer in the fish pond.

The fowls which are proven for their ability to produce more and large eggs as in the case of layers, or rapid body weight gains is in the case of broilers are selected along with fish.

The poultry birds under deep litter system should be fed regularly with balanced feed according to their age. Grower mash is provided to the birds during the age of      9-20 weeks at a rate of 50-70 gm/bird/day, whereas layer mash is provided to the birds above 20 weeks at a rate of 80-120 gm/bird/day. The feed is provided to the birds in feed hoppers to avoid wastage and keeping the house in proper hygienic conditions.

b. Egg laying:

Each pen of laying birds is provided with nest boxes for laying eggs. Empty kerosene tins make excellent nest boxes. One nest should be provided for 5-6 birds. Egg production commences at the age of 22 weeks and then gradually decline. The birds are usually kept as layers upto the age of 18 months. Each bird lays about 200 eggs/yr.

c. Harvesting:

Some fish attain marketable size within a few months. Keeping in view the size of the fish, prevailing rate and demand of the fish in the local markets, partial harvesting of table size fish is done. After harvesting partially, the pond should be restocked with the same species and the same number of fingerlings depending upon the availability of the fish seed. Final harvesting is done after 12 months of rearing. Fish yield ranging from 3500-4000 Kg/ha/yr and 2000-2600 Kg/ha/yr are generally obtained with 6 species and 3 species stocking respectively.

Eggs are collected daily in the morning and evening. Every bird lays about 200 eggs/year. The birds are sold after 18 months of rearing as the egg laying capacity of these birds decreases after that period. Pigs can be used along with fish and poultry in integrated culture in a two-tier system. Chick droppings form direct food source for the pigs, which finally fertilise the fish pond. Depending on the size of the fish ponds and their manure requirements, such a system can either be built on the bund dividing two fish ponds or on the dry-side of the bund. The upper panel is occupied by chicks and the lower by pigs.

Integrated fish-cum-duck farming

Integrated fish-cum-duck farming is the most common practice in China and is now developing in India, especially in West Bengal, Assam, Tamilnadu, Andhra Pradesh, Kerala, Bihar, etc. As ducks use both land and water as a habitat, their integration with the fish is to utilise the mutual benefits of a biological relationship. It is not only useful for fattening the ducks but also beneficial to fish farming by providing more organic manures to fish. It is apparent that fish cum duck integration could result in a good economic efficiency of fish farms.

The ducks feed on organisms from the pond such as larvae of aquatic insects, tadpoles, molluscs, aquatic weeds, etc., which do not form the food of the stocked fish. The duck droppings act as an excellent pond fertilizer and the dabbling of ducks at the pond bottom in search of food, releases nutrients from the soil which enhances the pond productivity and consequently increases fish production. The ducks get clean and healthy environments to live in and quality natural food from the pond for their growth. German farmer Probst (1934) for the first time, conducted experiments on integrated fish-cum-duck farming.

Benefits of fish–cum-duck farming

1. Water surface of ponds can be put into full utilization by duck raising.
2. Fish ponds provide an excellent environment to ducks which prevent them from infection of parasites.
3. Ducks feed on preda’tors and help the fingerlings to grow.
4. Duck raising in fish ponds reduces the demand for protein to 2 – 3 % in duck feeds.
5. Duck droppings go directly into water providing essential nutrients to increase the biomass of natural food organisms.
6. The daily waste of duck feed (about 20 – 30 gm/duck) serves as fish feed in ponds or as manure, resulting in higher fish yield.
7. Manuring is conducted by ducks and homogeneously distributed without any heaping of duck droppings.
8. By virtue of the digging action of ducks in search of benthos, the nutritional elements of soil get diffused in water and promote plankton production.
9. Ducks serve as bioaerators as they swim, play and chase in the pond. This disturbance to the surface of the pond facilitates aeration.
10. The feed efficiency and body weight of ducks increase and the spilt feeds could be utilised by fish.
11. Survival of ducks raised in fish ponds increases by 5 % due to the clean environment of fish ponds.
12. Duck droppings and the left over feed of each duck can increase the output offish to 5 Kg/ha.
13. Ducks keep aquatic plants in check.
14. No additional land is required for duckery activities.
15. It results in high production of fish, duck eggs and duck meat in unit time and water area.
16. It ensures high profit through less investment.

Pond managment:

This is similar to fish-cum-poultry farming. The stocking density can be reduced to 6000 fingerlings/ha. Fingerlings of over 10 cm size are stocked, as the ducks are likely to prey upon the small ones.

Use of duck dropping as manure:

The ducks are given a free range over the pond surface from 9 to 5 PM, when they distribute their droppings in the whole pond, automatically manuring the pond. The droppings voided at night are collected from the duck house and applied to the pond every morning. Each duck voids between 125 – 150 gm of dropping per day. The stocking density of 200 – 300 ducks/ha gives 10,000 – 15,000 kg of droppings and are recycled in one hectare ponds every year. The droppings contain 81 % moisture, 0.91 % nitrogen and 0.38 % phosphate on dry matter basis.

Duck husbandary practices:

The following three types of farming practice are adopted.

1. Raising large group of ducks in open water

This is the grazing type of duck raising. The average number of a group of ducks in the grazing method is about 1000 ducks. The ducks are allowed to graze in large bodies of water like lakes and reservoirs during the day time, but are kept in pens at night. This method is advantageous in large water bodies for promoting fish production.

2. Raising ducks in centralised enclosures near the fish pond

A centralised duck shed is constructed in the vicinity of fish ponds with a cemented area of dry and wet runs out side. The average stocking density of duck is about 4 – 6 ducks/sq.m. area. The dry and wet runs are cleaned once a day. After cleaning the duck shed, the waste water is allowed to enter in to the pond.

3. Raising ducks in fish pond

This is the common method of practice. The embankments of the ponds are partly fenced with net to form a wet run. The fenced net is installed 40 – 50 cm above and below the water surface, so as to enable the fish to enter into the wet run while ducks cannot escape under the net.

4. Selection of ducks and stocking

The kind of duck to be raised must be chosen with care since all the domesticated races are not productive. The important breeds of Indian ducks are Sylhet Mete and Nageswari. The improved breed, Indian runner, being hardy has been found to be most suitable for this purpose, although they are not as good layers as exotic Khaki Campbell. The number of ducks required for proper manuring of one hectare fish pond is also a matter of consideration. It has been found that 200 – 300 ducks are sufficient to produce manure adequate enough to fertilize a hectare of water area under fish culture. 2 – 4 months old ducklings are kept on the pond after providing them necessary prophylactic medicines as a safeguard against epidemics.

5. Feeding

Ducks in the open water are able to find natural food from the pond but that is not sufficient for their proper growth. A mixture of any standard balanced poultry feed and rice bran in the ratio of 1:2 by weight can be fed to the ducks as supplementary feed at the rate of 100 gm/ bird/day.

The feed is given twice in a day, first in the morning and second in the evening. The feed is given either on the pond embankment or in the duck house and the spilled feed is then drained into the pond. Water must be provided in the containers deep enough for the ducks to submerge their bills, along with feed. The ducks are not able to eat without water. Ducks are quite susceptible to afflatoxin contamination, therefore, mouldy feeds kept for a long time should be avoided. The ground nut oil cake and maize are more susceptible to Aspergilus flavus which causes aflotoxin contamination and may be eliminated from the feed.

6. Egg laying

The ducks start laying the eggs after attaining the age of 24 weeks and continue to lay eggs for two years. The ducks lay eggs only at night. It is always better to keep some straw or hay in the corners of the duckhouse for egg laying. The eggs are collected every morning after the ducks are let out of the duck house.

7. Health care

Ducks are subjected to relatively few diseases when compared to poultry. The local variety of ducks are more resistant to diseases than other varieties. Proper sanitation and health care are as important for ducks as for poultry. The transmissible diseases of ducks are duck virus, hepatitis, duck cholera, keel disease, etc. Ducks should be vaccinated for diseases like duck plague. Sick birds can be isolated by listening to the sounds of the birds and by observing any reduction in the daily feed consumption, watery discharges from the eyes and nostrils, sneezing and coughing. The sick birds should be immediately isolated, not allowed to go to the pond and treated with medicines.

8. Harvesting

Keeping in view the demand of the fish in the local market, partial harvesting of the table size fish is done. After harvesting partially, the pond should be restocked with the same species and the same number of fingerlings. Final harvesting is done after 12 months of rearing. Fish yield ranging from 3500 – 4000 Kg/ha/yr and 2000 – 3000 Kg/ha/yr are generally obtained with 6 – species and 3 – species stocking respectively.

The eggs are collected every morning. After two years, ducks can be sold out for flesh in the market. About 18,000 – 18,500 eggs and 500 – 600 Kg duck meat are obtained.

Integrated fish–cum–pig farming

The raising of pigs with fish by constructing pig – sties on the pond embankment or near the pond so that the pig wastes are directly drained into the pond or lifted from the pig house and applied to the pond. The pig dung acts as an excellent pond fertilizer, which raises the biological production of the pond, and this, in turn, increases the fish yield. The fish also feed directly on the pig excreta which consists of 70 % digestible feed for the fish. No supplementary fish feed or pond fertilization is required in this integrated system. The expenditure on fish culture is drastically reduced as the pig excreta acts as a substitute for fish feed and pond fertilization which accounts for 60 % of the input cost in the fish culture. This system has a special significance as it can improve the socio-economic status of rural poor, especially the tribal community who traditionally rear pigs.

Benefits of fish-cum-pig farming

1. The fish utilize the food spilled by pigs and their excreta which is very rich in nutrients.
2. The pig dung acts, as a substitute for pond fertilizer and supplementary fish feed, hence, the cost of fish production is greatly reduced.
3. No additional land is required for piggery operations.
4. Cattle foder required for pigs and grass are grown on the pond embankments.
5. Pond provides water for washing the pig – sties and pigs.
6. It results in high production of animal protein per unit area. 7. It ensures high profit through less investment.
7. The pond muck which gets accumulated at the pond bottom due to constant application of pig dung, can be used as fertilizer for growing vegetables and other crops and cattle foder.

Pond management practices:

Pond management is very important to get good production of fish. The management techniques like selection of pond, clearance of aquatic weeds and unwanted fish, liming stocking and health care are similar to fish-cum- poultry system.

Use of pig waste as manure:

Pig – sty washings including pig dung, urine and spilled feed are channeled into the pond. Pig dung is applied to the pond every morning. Each pig voids between 500-600 Kg dung/year, which is equivalent to 250-300 Kg/pig/6 months. The excreta voided by 30 – 40 pigs is adequate to fertilize one hectare pond. When the first lot of pigs is disposed off after 6 months, the quantity of excreta going to the pond decreases. This does not affect the fish growth as the organic load in the pond is sufficient to tide over for next 2 months when new piglets grow to give more excreta. If the pig dung is not sufficient, pig dung, can be collected from other sources and applied to the pond.

Pig dung consists 69 – 71 % moisture, 1.3 – 2 % nitrogen and 0.36 – 0.39 phosphate. The quality and quantity of excreta depends upon the feed provided and the age of the pigs. The application of pig dung is deferred on the days when algal blooms appear.

Pig husbandry practices:

The factors like breed, strain, and management influence the growth of pigs.

a. Construction of pig house: Pig houses with adequate accommodation and all the requirements are essential for the rearing of pigs. The pigs are raised under two systems the open air and indoor systems. A combination of the two is followed in fish cum pig farming system. A single row of pig pens facing the pond is constructed on the pond embankment. An enclosed run is attached to the pen towards the pond so that the pigs get enough air, sunlight, exercise and dunging space. The feeding and drinking troughs are also built in the run to keep the pens dry and clean. The gates are provided to the open run only. The floor of the run is cemented and connected via the drainage canal to the pond. A shutter is provided in the drainage canal to stop the flow of wastes to the pond.

The drainage canal is provided with a diversion channel to a pit, where, the wastes are stored when the pond is filled with algal bloom. The stored wastes are applied according to necessity.

The height of the pig house should not exceed 1.5 m. The floor of the house must be cemented. The pig house can be constructed with locally available materials. It is advisable to provide 1 – 1.5 square meter space for each pig.

b. Selection of pigs: Four types of pigs are available in our country -wild pigs, domesticated pigs or indigenous pigs, exotic pigs and upgraded stock of exotic pigs. The Indian varieties are small sized with a slow growth rate and produce small litters. Its meat is of inferior quality. Two exotic upgraded stock of pigs such as large – White Yorkshire, Middle – White Yorkshire, Berkshire, Hampshire and Hand Race are most suitable for raising with fish culture. These are well known for their quick growth and prolific breeding. They attain slaughter maturity size of 60 – 70 Kg within six months. They give 6 – 12 piglets in every litter. The age at first maturity ranges from 6 – 8 months. Thus, two crops of exotic and upgraded pigs of six months each, are raised along with one crop of fish which are cultured for one year. 30 – 40 pigs are raised per hectare of water area. About two months old weaned piglets are brought to the pig-sties and fattened for 6 months, when they attain slaughter maturity, are harvested.

c. Feeding: The dietry requirements are similar to the ruminants. The pigs are not allowed to go out of the pig house where they are fed on balanced pig mash of 4 Kg/pig/day. Grasses and green cattle fodder are also provided as food to pigs. To minimize food spoilage and to facilitate proper feeding without scrambling and fighting, it is better to provide feeding troughs. Similar separate troughs are also provided for drinking water. The composition of pig mash is a mixture of 30 Kg rice bran, 15 Kg polished rice, 27 Kg wheat bran, 10 Kg broken rice, 10 Kg groundnut cake, 4 Kg fish meal, 3 Kg mineral mixture and 1 Kg common salt. To reduce quantity of ration and also to reduce the cost, spoiled vegetables, especially the rotten potatoes can be mixed with pig mash and fed to pigs after boiling.

d. Health care: The pigs are hardy animals. They may suffer from diseases like swine fever, swine plague, swine pox and also infected with round worms, tapeworms, liver flukes, etc. Pig – sties should be washed daily and all the excreta drained and offal into the pond. The pigs are also washed. Disinfectants must be used every week while washing the pig – sites. Piglets and pigs should be vaccinated.

e. Harvesting: Fish attain marketable size within a few months due to the availability of natural food in this integrated pond. According to the demand of fish in the local market, partial harvesting is done. After the partial harvest, same number of fingerlings are introduced into the pond as the fish harvested. Final harvesting is done after 12 months of rearing. Fish yield ranging from 6000 – 7000 Kg/ha/yr is obtained. The pigs are sold out after rearing for six months when they attain slaughter maturity and get 4200 – 4500 Kg pig meat.

Integrated fish-cum-cattle farming

Fish farming by using cattle manure has long been practiced in our country. This promotes the fish-cum-cattle integration and is a common model of integration. Cattle farming can save more fertilizers, cut down fish feeds and increase the income from milk. The fish farmer not only earns money but also can supply both fish, milk and beef to the market.

Pond management practices:

These practices are similar to poultry or pig or duck integration with fish. Cow dung is used as manure for fish rearing. About 5,000 -10,000 Kg/ha can be applied in fish pond in instalments. After cleaning cow sheds, the waste water with cow dung, urine and unused feed, can be drained to the pond. The cow dung promotes the growth of plankton, which is used as food for fish.

Cattle husbandry practices:

The cow sheds can be constructed on the embankments of the fish farm or near the fish farm. The locally available material can be used to construct the cow shed. The floor should be cemented. The outlet of the shed is connected to the pond so that the wastes can be drained into the pond.

Cultivable varieties of cows are black and white (milk), Shorthorn (beef), Simmental (milk and beef), Hereford (beef), Charolai (beef), Jersey (milk and beef) and Qincuan draft (beef).

Integrated fish – cum – prawn culture

Through a lot of work has been done on composite fish culture incorporating Indian major carps and exotic carps having different feeding habits, and a considerable production achieved, no large scale polyculture of prawns and fish has been attempted. The culture of the surface and column feeding carps and bottom feeding prawns could be taken up as a polyculture practice in Indian waters to gain maximum yield. In this polyculture system, the culture of carps and freshwater prawns is more common than that of brackish water prawns with other fish.

Pond preperation:

The ideal size of the production ponds for polyculture is 0.2 ha. The pond size can go up to 0.1 – 1 ha area and would be conducive for netting, harvesting and other management practices. The optimal depth required is 0.7 – 1.0m, and it can even go upto 1.5 m. This depth is suitable for netting operations. The slope of the wet side bunds may be 1.3 and of the dry side bunds 1.2. Prawns use their appendages to crawl on wet lands during the night, specially during rain. Therefore, bunds may be kept 1 – 1.5 m wide and 0.5 m. height over the water level to prevent their movement from one pond to another. Drainable ponds may be more convenient and relatively inexpensive for complete harvesting and good management. Draining out water is desirable for water exchange so as to maintain favourable water quality during the culture period, for exposing bottom of ponds to sun and air, and for removal of silt and organic matter for improving the bottom soil. Such ponds having complete water flow or water circulation would enhance the production.

Application of lime and fertilizers:

Depending on the nature of the pond bottom, lime should be administered. Quick lime may be applied at the rate of 1000 Kg/ha. The water usable for the production ponds should have a pH of 7 – 8.5. If the pH of the water goes above 8.5, the same may be stagnated in the ponds for about 2 – 4 weeks prior to stocking with seed. Monthly or installment application of lime is essential to maintain pH, dissolved oxygen, hardness as well as calcium content in the water. If the pH is lower than 6.5, then the growth rate may suffer and moulting of prawns is delayed which may cause disease susceptibility and mortality of the prawns. Prawns utilise calcium from the water for their exoskeleton formation and therefore the calcium level in the water is likely to drop.

As prawns feed mainly on detritus, production ponds intended for monoculture of prawns need not be fertilized. However, for growing prawns and carps together, the ponds need to be fertilized just as in composite fish culture ponds. The ponds are first fertilized with organic manure like cowdung at the rate of 10 – 20 t/ha. It is better if a part of this manure is dissolved and added in the pond water 15 days before the release of fish and prawn seeds. The rest is added monthly in equal instalments. The other chemical fertilizers to be added are ammonium sulphate, urea, superphosphate and muriate of potash at the rate of 450, 200, 250 and 40 Kg/ha respectively and are added in equal instalments. Mahua oil cake can also be used as biocide as well as fertilizer at the rate of 200 – 250 ppm.

Stocking:

After three weeks of application of lime and fertilizers, quality seed is stocked during the morning hours. It is always better to acclimatise the seed to the pond conditions by keeping them for about 10 – 15 minutes in the pond before release. Sometimes heavy mortality occur due to wide variation in water pH between the pond and seed container. Therefore, it is always desirable to keep the transport seed for a few hours or even for a day in pond water for acclimatisation. To ensure good survival four week old juvenile prawns and carp fingerlings could be stocked. Soon after release into the pond, prawn seed disperses in different directions and either take shelter at the pond bottom or close to the submerged vegetation.

The stocking density of prawns in polyculture may be reduced to 50% of monoculture, i.e. 15,000 – 25,000 juveniles / ha for good growth and production. The size range of 30 – 50 mm is ideal for stocking. The freshly metamorphosed post – larvae are stocked in nursery tanks for a short duration (30 – 45 days) to raise the juveniles of size 30 – 50 mm. This helps to ensure good survival in culture pond and it is possible to have two crops a year with judicious stocking. Stock manipulation through selective harvesting of marketable prawns and restocking of juveniles is also recommended.

Prawns are omnivorous and are bottom feeders. Therefore, while selecting fish it is better if the bottom feeding common carp, mrigal, kalbasu, tilapia, etc. are avoided as they compete both for space and feed at the bottom. Compatible fish like catla, rohu, silver carp, grass carp, etc. are recommended for stocking with prawn juveniles. Carps being nonpredatory, competition for space or food does not occur to any noticeable extent. The juveniles or adult prawns do not prey upon or injure the fish. Directly or indirectly, the faecal matter of the fish may serve as a source of food for the prawns. Generally 3000 – 7000 fish seed per hectare is the appropriate stocking density under intensive fish farming. But stocking of carps fingerlings 1500 – 3000/ha is the ideal density for culture with prawn. Juveniles of 30 – 50 mm size are desirable for stocking to get better growth and survival in the pond. Catla, rohu, silver carp and grass carp may be stocked in the ratio of 2 : 1 : 2 : 1.

Food and feeding:

Natural feed like plankton are available through biological process. Pond fertilization, liming and even supplementary feeding help to maintain natural productivity in culture pond. It is very essential to provide supplementary feed to enhance growth and production under culture operations. Feed of cheap and abundantly available local variety like crushed and broken rice and rice products, groundnut and coconut oil cake, poultry feed, corn, peanut cake, soybean cake, small shrimps (Acetes), foot of apple snail (Pila), bivalve meat and prawn waste from freezing plant, trash fish or any fish or any non – oily inexpensive fish, squid meat, butcher waste, etc., in nutritionally balanced form is provided as supplementary feed. The feed may be given once or twice in a day at the rate of 5 – 10 % body weight. Feeds containing about 40 % protein have been found to give better growth. For carps particularly during the periods of absence of live food (plankton) in pond, food balls of ground nut oil cake and brawn rice mixed in the ratio of 1 : 1 may be given.

Production and harvesting:

As these prawns attain marketable size in about five months, two crops of prawns could be produced in a year. Mixed culture of M.malcolmsonii with Indian major carps and minor carps indicated higher growth production rate and survival (Rajyalakshmi et al, 1979, Venkateswaram et al, 1979). Maximum production of 327 Kg of prawns and 2,084 Kg of fish was achieved at 30,000 / ha mixed stocking rate. Under a system of stocking twice and repeated harvesting Ramaraju etal (1979) and Rajyalakshmi et al (1983) reported a production of 900 Kg/ha/year of the same species. About 1000 Kg/ha/year of prawns and 3000 Kg/ha/year of fish can be obtained from the polyculture system. M. rosenbergii could be cultured along with milk fish and mullets in brackish water ponds with a 12 – 25 % salinity. An individual growth of 100 gr/ 5 months has been reported with a stocking density of 29,000 -1,66,600 /ha.

In prawn culture, either in monoculture or polyculture, early harvest is better for good returns. Unlike fishes, prawns take feed and moult very frequently during the process of growth. If the harvesting time is prolonged, chances of cannibalism is more and this ultimately affects the survival rate. Two principal methods are generally followed to harvest the prawn. Intermittent harvest is carried out to remove the larger prawns. The other method is complete harvesting at the end of culture. Generally the fishes are harvested only after 12 months. By adopting the above stated techniques it is possible to obtain prawn production of over one ton/ha/yr with average survival of 50 % in either one or two crops and over 3 tons/ha/yr fish with survival of 50 – 80 %. Farming for this should be done with proper management and measures.

Integrated fish farming web:

Various types of combinations of aquaculture, agriculture, animal husbandry and horticulture can constitute the integrated fish farming web. Integrated fish cultures attuned economically and socially for rural development treats the water and land economically and socially for rural development. It treats the water and land ecosystem as a whole with the good of producing valuable protein from wastes, changing ecological damage into benefits and sustaining local circulation of resources. This strategy of ecological aquaculture can not only increase fish production and further improve ecological efficiency but also improves social and ecological upliftment. It is not only useful in the development of fish culture but will also improve the quality of the environment. The control water of quality by means of fertilization takes priority in fish culture management. The fish pond is a living habitat for fish, a culture base for living food organisms and a place of oxygenation of decomposed organic compounds. These properties determine the characteristics of the input and output of matter and energy in integrated fish culture.

Summary

In olden days, the average yield of fish from ponds was as low as 500 kg/ha/yr. This quantity is considered as very poor. In composite fish culture more than 10,000/kg/ha/yr fish yield can be obtained in different agro-climatic regions of our country.

Monoculture is the culture of a single species of fish in a pond. 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.

Fishes can be reared in paddy, wheat and coconut fields. Fruiting, flowering plants and vegetable plants are cultivated on the dykes. Azolla – fish culture is also becoming popular.

 

 

 

Source: Aquaculture