Fish culture is the rational cultivation of fish in a confined water area where the practices of both agriculture and animal husbandry are applicable. The soil and water management aspect of fish culture practice involving application of organic manures and inorganic fertilizers for the production of microscopic plants, the phytoplankton, is basically similar to agriculture while husbandry of fish such as feeding, breeding and health care is more or less similar to a livestock farming system. This farming system is also unique in that the farmed animal is cold-blooded or poikilothermic and lives in a water medium. Although this fish farming is approximately 2 000 years old, the importance of it has been realized only recently in the face of mounting pressure on land resources and scarcity of animal protein for the ever increasing human population. While introducing fish culture, it seems reasonable to discuss certain important aspects of fish farming systems and their relevance to the rural development programme of developing countries.
Malnutrition and starvation are the two serious problems being faced by millions of rural poor in most of the developing countries. The problem of malnutrition is in fact more serious and of a bigger dimension than the starvation problem and is caused mainly due to animal protein-deficient diets. Animal protein is essential for proper growth, repair and maintenance of body organs and tissues. Fish contain about 16–20% protein compared to about 12% in egg, 3.5% in milk and 6–8% in rice and wheat. Moreover, it is wholesome, tasty, highly nutritive and an excellent source of essential minerals, vitamins and essential amino acids. At present about 31% of the total animal protein supply in the Asian region is in the form of fish protein. For the poorest segments of the population, fish is not only the most important animal protein source, but often the only one.
The reproductive potential of fish compared to any other farmed animal is also very high. A kilogram of female cultivable carp species yields on an average about 0.1 million eggs, each of which has the potential to become 1 kg fish in about a year. No livestock animal possesses this magnitude of fecundity. Although fish needs water as a medium to survive and grow, it consumes minimal quantity of water compared with any livestock or agricultural crop. Fish also enriches the water with its voided metabolites thus making the water more productive for agriculture.
Fish culture systems require a relatively less amount of energy for protein production than any other farming system. Carp culture, depending upon culture practices, requires energy at the rate of 22–468 KJ/g of protein production while a land animal farming system needs over 550 to 3 400 KJ/g.
Fish are cold blooded or poikilothermic animals. In other words they cannot maintain a constant and high body temperature like other livestock animals. Instead, their body temperature fluctuates according to the surrounding temperature. In warmer climates, their metabolism accelerates and they grow faster, while in colder climates, the metabolic rate slows down, resulting in a reduced rate of growth. In this way they save energy by not spending it for maintaining a higher and constant body temperature.
Although the world's total marine production now stands at more than 80 million tons per year, all trends indicate that a saturation point is quickly approaching. During the past decade the growth rate hovered around 2%, much lower than earlier decades.
On the other hand, tremendous potential exists in aquaculture. Aquaculture presently produces over 8 million tonnes of fish and shellfish annually. It is estimated that Asian aquaculture production could be raised to 20–30 million tonnes a year by the end of the century. Aquaculture production has increased at an annual growth rate of nearly 7% between 1975–84.
Aquaculture is also considered to be a potential source of employment for poor farmers and displaced capture fishermen. Rapid development of aquaculture has already generated considerable employment through culture of marketable fish, fish seed production, and marketing of fish and fish seed. The National Agriculture Commission of India while estimating the employment potential of fish culture has indicated that every tonne of fish produced provides employment to 2.5 persons.
The other important advantages of fish farming are that the production is carried out within easy reach of consumers and also the harvesting can be adjusted to demand, thus minimising distribution problems and spoilage.
Rural ponds in Asia, hitherto producing at subsistence level, have succeeded in increasing production per unit area through improved culture practices involving higher stocking densities, polyculture combinations, pond manuring and feeding. The switch over from monoculture practice to polyculture has significantly contributed toward higher production and the prospect of polyculture appears very bright as the fish seed of desired species is becoming easily available due to the establishment of a large number of hatcheries. During recent years, advances have also been made in traditional aquaculture systems practised in rural India by the development of composite fish culture, a system of polyculture of a group of complementary and supplementary freshwater species of fast growing carps in undrainable ponds. With the successful demonstration in different agroclimatic zones of India, gradual improvements in technology have been made and it is now possible to obtain a production rate of over 10 t/ha/yr in experimental ponds and up to about 5 t/ha/yr in farmers' ponds against the traditional average rate of production of 600 kg/ha/yr. To meet the increasing demand of seed of culturable carps, hypophysation techniques have also been developed for both Indian and Chinese carps and as a result they are now being bred in captivity even by fish farmers in remote villages. The emergence of this culture technology suitable for undrainable ponds and the simultaneous development of hypophysation techniques for fish seed production has completely revolutionized fish farm productivity.
This manual intends to provide the basic concept and practical guidelines of fish culture in undrainable ponds. Since it is prepared especially for extension agents and field workers, certain important things have been repeated and at times experimental results have been simplified with a view to making it more practical, simple and illustrative. It outlines the practices of procurement and propagation of fish seed, rearing of spawn to fry and fingerling stage, and production of table-size fish following simple sequential steps. Like other farming systems this culture system is also prone to certain unexpected hazards for which one has to be prepared and properly equipped. Such hazards are disease outbreaks, oxygen depletion, pollution, flood, drought, poaching, etc. The content of this manual is a synthesis of the author's personal field experience, the information gathered from published literature, and the observations of other workers in India. Based upon Indian experience, water resources in other developing countries with similar agroclimatic conditions may be utilized for the development of fish culture. It is hoped that this manual will serve as a practical guide to extension workers in popularizing freshwater fish culture in undrainable ponds.
