The most successful system of pond fish culture is the polyculture of three Indian major carp species - catla, rohu and mrigal along with three Chinese carps viz. silver carp, grass carp and common carp. In India this is commonly known as composite fish culture. The best results in terms of fish production in this system results not only through a judicious combination of species, but also due to appropriate management techniques including pond fertilization, supplementary feeding and health care. On the basis of growth performance of different species, modifications are often made in stocking density, species ratio, fertilization schedule and supplementary feeding programme in different agroclimatic conditions. High rates of fish production to the tune of over 5 500 kg/ha/6 months, 7 200 kg/ha/8 months and over 10 tonnes/ha/yr have been achieved in composite fish culture trials conducted in different agroclimatic conditions of India.
The carp culture system as a whole is operated as a three-tier culture system where the practices are adopted for rearing fish during their different stages till they are harvested. Spawn (post larvae) are reared upto fry (2–3 cm) stage in nursery ponds, fry to fingerlings (8–12 cm) in rearing ponds and finally fingerlings to table-size fish in composite fish culture ponds or stocking ponds. Relatively smaller, seasonal ponds are mainly used for rearing spawn to fry stage and harvested after 2–3 weeks. Several crops (3–4) of fry are usually taken during the season. Pond fertilization by cattle manure and feeding with 1:1 mixture of oil cakes and rice bran is the usual practice. Fry raised in nurseries are reared upto fingerlings in slightly bigger ponds (0.05 – 0.1 ha) of seasonal or perennial in nature. Fingerlings are removed after 3 months and stocked in composite fish culture ponds.
An integrated approach of composite fish culture together with compatible combination(s) with poultry, duckery, pig rearing and cattle raising is now being adopted. Under this system of farming small livestock and farm yard animals, viz. pigs, poultry, ducks, etc., are integrated with composite fish culture by siting animal housing units on the pond embankments in such a way that the animal wastes and washings are diverted into fish ponds for recycling. The fish not only utilize spilled animal feed but also directly feed on fresh animal excreta which is partially digested and is rich in nutrients. Surplus excreta supports the rich growth of planktonic fauna. Fertilizers and supplementary feed are not used, resulting in drastic cost reduction (Sharma et al., 1979; 1979a). Production potential through integrated carp farming is summarised in Table 4.
|Integration||Fish production||Animal production (live weight)|
|Pig farming||6 – 7 ton/ha||4 000–5 000 kg pig meat|
|Duck farming||3 – 4 ton/ha||500 kg duck meat + 17 000–20 000 eggs|
|Poultry farming||4–5 ton/ha||60 000–70 000 eggs + 1 500– 2 000 kg meat|
The salient features of the various types of livestock/carp integrated culture systems are described below.
Pigstyes are constructed either on the pond embankment or near the pond to facilitate easy drainage of waste directly into the pond which acts as pond fertilizer and supports dense growth of natural fish food organisms (Figs.9A and 9B). Besides, fish also feed directly on the pig excreta. No other feed or fertilizer is applied to the pond. A pond is prepared by following the usual pond preparation techniques (Section 9.1) and stocked with fingerlings of all the six species of carps cultured under composite fish culture at higher of 8 000–9 000/ha with surface, column, bottom feeders and grass carp in the ratio of 40:20:30:10. Marketable size fish are sold by partial harvesting while final harvesting is done only after 12 months of farming.
About 2 months-old weaned piglets are fattened for six months when they attain slaughter size (60–70 kg) and similarly a second crop is raised within the next six months. About 30–40 pigs should be kept for proper fertilization of the pond. Pigs are fed on mash at an average rate of 1 kg/day. Green grasses or animal fodder is also provided. Grass with interlocked soil in root system (sod) are provided once a week to avoid mineral deficiency.
Grass carp is fed with aquatic weeds or green animal fodder.
Fish yields ranging from 6 000–7 000 kg/ha/yr are generally obtained.
This is also an efficient integrated system based on the principle of waste recycling. Pond preparation technique is basically the same. A duck house is normally constructed on the pond embankment or on the pond water on a floating platform (Figs. 10A and 10B). When given free range, ducks feed on aquatic organisms such as insect larvae, tadpoles, molluscs, weeds, etc. The duck droppings like pig excreta act as fertilizer. Ponds are prepared and stocked with fingerlings of all the six carp species at 6 000 ha with surface, column, bottom feeder and grass carp in the ratio of 40:20:30:10. Fingerlings of over 10 cm are preferred for stocking. About 200–400 ducks are sufficient to adequately fertilize a l ha pond. Normally 2–3 months old ducklings are preferred. Although ducks are able to feed upon natural food from the pond, they are also provided with duck feed at the rate of 100 g/bird/day. Ducks start laying after 5–6 months and continue for 2 years. Fish yields ranging from 3 000–5 000 kg/ha/yr are generally obtained.
Figure 9a. Fish-cum-pig farming (wooden pigsty)
Figure 9b. Fish-cum-pig farming (concrete pigsty)
Figure 10a. Fish-cum-duck farming (duck house in pond)
Figure 10b. Fish-cum-duck farming (duck house in pond dyke)
Under this system of integration the poultry birds are raised in cages under a shed normally constructed over the pond embankments or in the vicinity of the pond. The space requirement in such a system of poultry raising is about 1 sq.ft. per bird. The droppings of the birds fall on the floor from where these are collected and applied to the pond. The chicken house can also be built directly over the pond water so that the excreta may fall in the pond water underneath. Usually, 400–600 chickens/ha of pond water surface are used. No feed or fertilizer is applied in the pond, except aquatic vegetation for the grass carp. Fish production at the rate of 4–5 t/ha is possible using this system.
In India, this system of freshwater fish culture has assumed greater significance in view of its potential role in recycling of organic wastes and in integrated rural development (Sinha, 1981).
Besides freshwater ponds, there are many low-lying areas which become waterlogged during the rainy season. In course of time these areas get infested with dense aquatic vegetation and turn into swamps. Swamps are also formed along the irrigation canals due to profuse seepage. These areas are best suited for culturing airbreathing fishes such as Koi (Anabas testudineus), Singhi (Heteropneustes fossilis), Magur (Clarias batrachus) and Murrels (Channa sp.) without getting involved in costly processes of their reclamation essentially needed for carp culture. There are three levels of culture practices viz. low cost culture, semi-intensive culture and intensive culture depending on inputs and level of management (Dehadrai, Murugesen and Pathak, 1979).
Fingerlings (6–10 g) and feed are the two material inputs used in the culture system. Fertilizer is not used. However, replenishment of water becomes an essential input in case of intensive system of culture in ponds where very high stocking rate and intensive feeding is practised to obtain very high yields (Dehadrai, Kamal and Das, 1985). Monoculture as well as polyculture of these fishes are commonly undertaken, yielding production to the tune of 3 000 to 7 000 kg/ha/yr. Production at the rate of over 3 000 kg/ha/8 months is possible through monoculture of Channa marulius in swampy ponds. In intensive system of monoculture of magur and singhi with frequent change of water, yields of over 15 t/ha/yr have been obtained. Presence of naturally occurring weeds in airbreathing fish culture ponds not only provide protection against poachers, but also encourage the growth of insects which are consumed by the fish. The common culturable species are magur (Clarias batrachus), singhi (Heteropneustesfossilis), murrels (Channa marulius, Channa striatus and Channa punctatus) and Koi (Anabas testudineus).
The wastes, including sewage and waste water produced by the human community hold high potential for fish production. In India itself there are about 150 sewage-fed fish farms covering an area of about 12 000 ha. Very high production in the order of 7–10 tonnes/ha/yr has been obtained from ponds fed with sewage which invariably contains high percentage of N,P,Ca,K,etc. An average production of about 7 t/ha/yr is easily obtained using a mix culture of 5 carp species (Ghosh et al., 1985). The sewage fed ponds are generally dewatered completely during summer so as to remove all the carnivorous fishes. The pond is initially fertilized by introducing partially treated sewage effluent upto about 75–80 cm and then clean water is pumped in to raise the pond water level to 1.5 m. Within a month the pond stabilises with respect to dissolved oxygen and becomes suitable for stocking with fish seed. During raising of marketable size fish, additional fertilization with sewage effluent is carried out in small doses every month and the pond is netted frequently to help oxygenate the water and in course of netting the marketable size fish are also harvested.