Fish Fauna of the Nile

Abstract

The total number of fish species in the Nile drainage basin, which includes the River Nile, its affluent rivers and the connected Lakes, is currently estimated at more than 800. Of these, 128 species, belonging to 27 families, occur in the River Nile. The river comprises many different habitats (e.g. the swampy Sudd) each with a different species composition. The families Cichlidae, Cyprinidae, Mormyridae and Mochokidae comprise the majority of the fish species in the Nile drainage basin. The Mormyridae and Mochokidae have more representatives in the river than in the Lakes. The same holds for the Cyprinidae, with the exception of Lake Tana that harbours almost as many cyprinid species as the river. Cichlid species dominate the fish faunas of Lakes Edward, George, Victoria and Kyoga. Especially Lakes Victoria and Kyoga and their satellite Lakes are well known for their cichlid diversity. Prior to the human induced ecological changes, these Lakes contained about 600 haplochromine cichlid species in contrast to 46 native fish species belonging to 11 other families. The haplochromine cichlids comprise at least 15 trophic groups that are morphologically adapted to feed on specific food types. The boom of the introduced Nile perch in the 1980s as well as fishery and habitat deterioration had a strong impact on the haplochromine species and many other fish species, and about 200 endemic haplochromine species may have gone extinct. In Lake Tana, which is part of the head waters of the Blue Nile, the fish fauna is dominated by the cyprinid genera Barbus and Labeobarbus. The flock of 15 endemic Labeobarbus species in this lake shows a trophic radiation similar to that of the haplochromine cichlids of Lake Victoria. Another notable inhabitant of Lake Tana is Nemacheilus abyssinicus, the only known representative of the Euro-Asiatic Balitoridae.