The role of nearshore areas and other refugia in survival of fishes especially haplochromines in Lake Victoria, with specific reference to Napoleon Gulf

Before introduction and establishment of the Nile perch Lales nilolicus, haplochromines were the most abundance group of fishes in Lake Victoria, Kyoga and Nabugabo. They formed at least 83%, by weight of the fish biomass in Lake Victoria up to early 1980s (Kudhongania & Cordone 1974, Okaronon el ai, 1985). They occupied virtually all trophic levels and played an important role in the flow of organic matter in these ecosystems. Each species had its own unique combination of food and habitat preference (van Oijen 1982, Goldschmidt el al 1990). Up to eleven trophic groups were identified in the Mwanza Gulf van Oijen op cit.). These included; phytoplanktivores, detritivores, algal grazers, plant eaters, molluscivores, parasite waters,phyoplanktivores, insectivores, piscivores, paedophages, and scale eaters. The detritivorous phytoplanktivores and the pelagic phytoplanktivores together constituted about 50% of the total haplochromine biomass in the lake (Goldschmidt 1986, Witte & van Oijen 1990).