Fish species and trophic diversity of haplochromine cichlids in the Kyoga satellite lakes (Uganda)

摘要

Prior to the 1980s, lakes Kyoga and Victoria previously supported an exceptionally diverse haplochromine fish fauna comprising at least 11 trophic groups. The species and trophic diversity in these lakes decreased when the introduced Nile perch depleted haplochromine stocks. From December 1996 to October 1998, we studied species and trophic diversity of haplochromine fishes in six satellite lakes without Nile perch in the Kyoga basin and compared them with the Kyoga main lake against historical data from Lake Victoria where Nile perch were introduced. Forty-one species were found in the study area, of which, the Kyoga satellite lakes contributed 37 species in comparison to only 14 from the Kyoga main lake. Analysis of trophic diversity based on 24 species that contained food material revealed seven haplochromine trophic groups (insectivores, peadophages, piscivores, algal eaters, higher plant eaters, molluscivores and detritivores) in the Kyoga satellite lakes in comparison to two trophic groups (insectivores and molluscivores) in the Kyoga main lake. Many of the species and trophic groups of haplochromines depleted by the introduced Nile perch in lakes Kyoga and Victoria still survive in the Kyoga satellite lakes. This is attributed to the absence of Nile perch in those lakes. Nile perch has been prevented from spreading into the satellite lakes by swamp vegetation that separate them from the main lakes. If these swamps prevent Nile perch from spreading into the lakes, it is possible to conserve fish species, especially haplochromines, which are threatened by introduction of Nile perch in the main lakes.