Distribution and association of Tilapine unit stocks in the Lake Victoria catchment (Kenya)

The Lake Victoria Catchment (Kenya) harbours six species of tilapia. Two species Oreochromis variabilis (L) and Oreochromis esculentus (L) are endemic while four species Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii(Gervais) and Tilapia rendalli(Gervais) were variously introduced in 1950s and early 1960s. The existence of six tilapia species in the same geographical range has had significant ecological and economical implications. The study investigated the ecological impacts by determining species diversity, distribution, association (allopatric, sympatric and parapatric) and habitat preferences for the six-tilapia species. Shannon-wiener index was used to determine diversity, while species distribution was evaluated on the basis of 39 habitats (dams and satellite lakes) within the catchment. Species associations were determined using Cole’s Cab index. The Shannon Weiner function values of 2.44-2.7 indicate relatively high species diversity in 15% of 33 habitats where Tilapia were resident. Cole’s Cab indices showed significant relationships in O. esculentus X O. variabilis, O.leucostictus X O. esculentus, O. niloticus X O. variabilis and O. niloticus X O. leucostictus at P < 0.05. Habitat preference for the six species is provided.

Published

Geographical distribution; Interspecific relationships; Associated species; Stocks; Freshwater fish; Inland fisheries; Catchment area; Endemic species; Biodiversity; Species diversity; Habitat selection; Check lists; Ecological associations; Introduced species;Oreochromis variabilis; Oreochromis esculentus; Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii; Tilapia rendalli