Inland Fisheries

1.1.2. Global freshwater fish biodiversity

Valid scientific descriptions exist for about 27,977 living species of fishes in 515 families and orders (Nelson, 2006). One third of the fish families have, at a minimum, one species with members spending at least part of their life in freshwater. Freshwater fish diversity is therefore large compared to other systems since freshwater lakes and rivers account for only 1% of the earth’s surface and < 0.01% of its water. According to Nelson, 2006, 11952 species are exclusively freshwater in origin. 

The largest number of species occurs in the tropics and the diversity of fishes, in general, increases from the poles to the tropics. For example in many Arctic lakes there is only one species, the Arctic char, Salvelinus alpinus (Johnson, 1983) compared to Lake Malawi which has at least 500 species of Cichlidae alone (Craig, 1992). The Paleoarctic region is species-poor. Southeast Asia, South America and Africa have the most freshwater fishes although many have not been described. For example the Amazon Basin has about 2,000 species, the Mekong Basin about 1,200 species and the Zaire system about 900 species.

However, only about 100 fish species, or species groups, are listed in FAO statistics as making up inland capture. In this regard, the quantification of the importance of individual species and of species groups as inland fishery resources is severely handicapped by the lack of reporting at these levels. Overall, some 45 percent of inland catch is aggregated as "freshwater fish not elsewhere included" (nei), 7 percent "freshwater molluscs nei" and 6 percent is "crustaceans nei".