National Agricultural Research Organisation (NARO), Fisheries Resources Research Institute (FIRRI), P.O. Box 343, Jinja, Uganda. E-mail: firi@infocom.co.ug

Conservation of fish species and trophic diversity in the Victoria and Kyoga Lake basins through protection of satellite lakes and refuge

Introduction of exotic fish species, especially the Nile perch Lates niloticus, is believed to have caused the decline of fish species and trophic diversity in the Lakes Victoria, Kyoga and Nabugabo. As well, approximately 60% of the haplochromine cichlids are thought to be extinct from Lake Victoria. We surveyed and made an inventory of the existing fish species in some specific habitats in the main Lakes Victoria and Kyoga, rivers, six and eight satellite lakes in the Victoria and Kyoga Lake basins respectively. Trophic diversity of haplochromines was also examined in only six satellite lakes of the Kyoga Lake basin. Kyoga satellite lakes recorded the highest fish species diversity, especially the haplochromines. Habitats with rocky outcrops and macrophyte cover are important refuge for endangered fish species in the main lakes. Labeo victorianus, a species believed to be extinct in Lakes Victoria and Kyoga, was present in the surveyed rivers. Seven trophic groups of haplochromines were recorded from the Kyoga minor lakes as compared to only two from Lake Kyoga and four from Lake Victoria. Most of the fish species and trophic groups of the haplochromines are depleted in Lakes Victoria and Kyoga as a result of predation by Nile perch. However, in Kyoga minor lakes where the Nile perch is absent, haplochromines are abundant. The Koki lakes and Kyoga minor lakes host Oreochromis esculentus, which are almost extinct in the main Lakes Victoria and Kyoga. Many of these satellite lakes, rivers and special habitats within Lakes Victoria and Kyoga should be protected for the conservation of fish species diversity. The swamp vegetation that separates some of the satellite lakes from the main lakes should be left intact to prevent Nile perch from spreading into these lakes.