The cichlids dominate the ichthyofauna of the Great African Lakes in a taxonomic sense and ecological demersal habitats. Lake Victoria possibly had more than 250 cichlid species prior to the Nile perch explosion of the 1980's; all the cichlids were endemic except O. niloticus, O. leucostictus and Tilapia (Coptodon) zillii/Tilapia (C.) rendalli. The deep and oligotrophic Lake Tanganyika has more than 140 cichlid species (all endemic) whereas Lake Malawi has still more than 400 cichlid species all of which except four are endemic. More detailed information on the species assemblages of Lakes Victoria, Tanganyika and Malawi is given by Van Oijen et al (1981). Brichard (1978) and Ribbink et al (1983) respectively. The broad characteristics of the ichthyofauna described by Lowe-McConnell (1977), Lowe-McConnell (1975), Roberts (1975), Bowmaker et al. (1978) and Poll (1980) explain well the predominance of Heterotis (Ostreoglossidae) Mormyriade, Characidae, Citharinidae, Ciprinidae, Bagridae, Clariidae, Schilbeidae in riverine systems. They also give good reasons for the predominance of cichlids in the African Great Lakes. In Lake Victoria the abundance of family Cichlidae accounts for more than 87% known species whereas in Lake Tanganyika, cichlids account for 78% of the taxa. Lake Malawi has the richest assemblage of cichlids (about 92% of the species occuring in the Lake). Detailed information on exploited cichlids and tilapias is given by Thys van den Audenaerde (1968) and Trewavas (1933, 1983).
The family Clupeidae is important in Lake Tanganyika where Stolothrissa and Limnothrissa still support fisheries in Burundi, Tanzania, Zaire and Zambia. Information available from the fishermen and scientists with working experience on Lake Tanganyika, indicate that Limnothrissa and Stolothrissa are now somewhat on the decline.
The Cypriniadae (cyprinids) are generally still abundant in Great Lakes of Africa, particularly Rastrineobola argentea which is booming in Lake Victoria. However there is a sad story of Labeo which has been overexploited in rivers and inshore lacustrine areas. Barbus spp. are somewhat more resilient to exploitation.
Among the cichlids (Cichlidae) Oreochromis niloticus (the Nile tilapia) still supports good fisheries in Lakes Mobutu Sese Seko, Edward (elsewhere referred to as Idi Amin) and Victoria (where it was introduced). Oreochromis niloticus has declined considerably in Lake Turkana. Species of Oreochromis (Nyasalapia) of Lake Malawi (=Lake Nyasa) are still important and contribute to fish catches. Many other tilapiine cichlids have declined in the Great Lakes due to easy accessibility in inshore waters and owing to the use of small mesh-size gillnets.
As far as the Siluroidei, the families Clariidae, Bagridae and Synodontidae are well represented in the African Great Lakes. Many countries bordering the African Great Lakes do not yet provide separate catch data for these species. Hence, it is difficult to ascertain the significance of Clarias, Bagrus, and Synodontis for most of the lakes. In Lake Victoria, however, there are indications that stocks of Clarias and Bagrus are declining. Synodontis spp. are still surviving because Nile perch and other predators do not dare to prey on this species. Schilbe inhabiting shallow riverine and lacustrine areas are vulnerable to the small mesh-sized gillnets and beach seines but they display resilience to exploitation.
