People have been farming fish for thousands of years and a wide range of plants and animals are currently grown in aquaculture. In 1997, freshwater aquaculture (predominately finfishes) accounted for over 45 percent of the total world aquaculture production. Plants and molluscs from marine waters contributed about 20 and 24 percent respectively. Brackishwater aquaculture currently contributes less than 5 percent to the world total (by weight), however, as production is mainly shrimp, its share by value is about 15 percent.
In 1997, the top-ten aquaculture species by weight were all low in the food chain, either primary producers, filter feeders or finfish that, as adults, are herbivores or omnivores. The top species was kelp, Laminaria japonica, which totalled just over 4 million tonnes. The others on the list included several kinds of carp, the Pacific cupped oyster, the Yesso scallop, the Japanese carpet shell and the Nile tilapia.
Asia is the world leader in aquaculture production, with China alone producing about two-thirds of the world's total. Several low-income food-deficit countries (LIFDCs) are big aquaculture producers. In these countries aquaculture contributes to poverty alleviation and to the enhanced supply of fish products to resource-poor people in rural and urban areas.
Many developing countries export aquaculture products, and in many cases aquaculture has become a major source of hard currency, which is used to invest in further development or to service foreign debts.
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