Defining aquaculture

With the decrease in marine fish production there is a greater emphasis on producing fish from inland and brackish water bodies. This includes fish cultured in tanks, ponds, lakes, reservoirs, rivers, brackish-water bodies, etc. Historically, China and India have been producing large quantities of cultured fish and they contribute to the bulk of fish production from aquaculture in the world.

The Food and Agriculture Organisation of the United Nations (FAO)defines aquaculture as "the farming of aquatic organisms, including fish, molluscs, crustaceans, and aquatic plants. Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. Farming also implies individual or corporate ownership of the stock being cultivated. For statistical purposes, aquatic organisms which are harvested by an individual or corporate body which has owned them throughout

their rearing period contribute to aquaculture, while aquatic organisms which are exploitable by the public as a common property resource, with or without appropriate licences, are the harvest of fisheries."

Culture activities can be of different kinds and can employ different techniques. Culture techniques can range from extensive to highly intensive methods. In the extensive system there is minimal human intervention whereas in the intensive system there is a great deal of dependence on various kinds of inputs like land, seeds and feed.

Culture activities can take place in a freshwater, brackish-water or seawater environment. Freshwater aquaculture is practised mostly in countries like China, India and Thailand mainly for species of carp. Brackish-water aquaculture is mainly for farming shrimp. It is practised primarily in the Asian countries. China, India, Indonesia and Thailand are big producers of farmed shrimp. Aquaculture in the sea is often referred to as mariculture and it is for species like clams, oysters etc. Japan has the biggest mariculture industry in the world. While

production from freshwater aquaculture is mainly for subsistence or for the domestic market,

that from the brackish-water is mainly for the export market. The harvest is almost entirely exported to countries like Japan, USA and the European Union.

The technology used in aquaculture could vary from labour intensive to capital intensive. The culture practices could vary from monoculture or polyculture to integrated farming. In monoculture only one species is grown whereas in polyculture several species are simultaneously grown. These species normally have feeding habits that do not clash with each other. In integrated farming systems fish is normally grown together with livestock such as pigs and poultry, and plants like mulberry. Outputs of one production sub-system are used as inputs by another.

Intensive and semi-intensive forms of farming could have several negative impacts. It is a well-known fact that shrimp farming using semi-intensive or intensive techniques have had numerous negative impacts. These have, for example, led to the incursion of salinity into coastal aquifers and rice growing areas, destruction of mangroves, subsidence of land and alienation of the village commons. Conversion of paddy fields to shrimp farms has caused considerable displacement and unemployment.