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The inland water fishes of Africa

 | 
Didier Paugy
, 
Christian Levêque
, 
Olga Otero

Fish communities in East African rift lakes

Jos Snoeks, Christian Levêque, Yves Fermon et Fabrice Duponchelle

Résumé

The Great Lakes of East Africa are unique systems in various ways. The region has been subject to much tectonic activity. Hence, some of the deepest lakes of the world can be found in the area, most of them stretched in a north-south direction in the western branch of the Rift Valley (figure 19.1). The elongated and deep lakes Tanganyika and Malawi, together with the saucer-shaped, relatively shallow Lake Victoria form the three largest freshwater bodies in the region. All three figure amongst the top ten largest lakes in the world in terms of surface and volume. Other large lakes in the region include Kivu, Edward (with George), Albert, Turkana, Mweru and Rukwa.
However, what really makes these lakes unique is their biodiversity and especially their fishes. Nowhere else in the world can one find a larger number of fish species than in these lakes. Not only is the sheer number of species exceptional, but most of these fishes are also endemic to a certain lake. Remarkably, the largest compound of the fish fauna, over 95% for the three large lakes, belongs to only one family, the Cichlidae. These cichlids represent the largest radiation of vertebrates in the world. Hence these lakes are considered natural laboratories for the study of evolution and speciation.

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Extrait du texte

While the fishes in these lakes represent an unparalleled biodiversity treasure, one should not forget that they are of prime importance as the largest source of animal protein for the riparian human population (Snoeks, 2001). It is clear that the exploitation and the conservation of these fishes give rise to conflicts. Increasing human activities in the region undeniably have a direct (fisheries) or indirect impact on the lake’s fish communities. This is likely to increase and the sustainable management of the ecosystems of the large African lakes will become a huge challenge. In this respect, one should also not forget that most of these lakes have relatively long to very long flushing times, which makes them highly vulnerable to pollution.

FIGURE 19.1. Major lakes of the East African Rift system.

Image

What determines the overall structure of the fish communities in these lakes is principally depth and substrate type. Depth distribution of fishes is limited by the oxycline. Therefore in ...

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