The Ecology of Lake Victoria

Nile perch was first recorded in Lake Victoria in 1960. Once its presence was confirmed, the British colonial governments in Uganda and Kenya proceeded with deliberate transfers (which had been under debate for several years). Over the next 25 years the Nile perch spread throughout the lake, but catches remained at a low level (of less than 5% of the total) until the 1980s. During this decade there was a dramatic change in the ecology of the lake, with Nile perch catches increasing in quantity, to an estimated 500,000 tonnes per annum, representing well over 90% of the biomass and 60% of the total catch. The indigenous tilapia have all but been replaced by the introduced Nile tilapia Oreochromis niloticus, and the only other significant fishery is for the small anchovy-like fish, the omena (Rastrineobola argentea). Lake Victoria once supported a vast range of closely related species of fish of the genus Haplochromis, occupying a diversity of ecological niches. However, there has been substantial decline in the haplochrome population; about half of the 400 original species have become extinct and many of the rest are under severe pressure, much to the concern of ecologists. Without a co-ordinated effort to preserve habitats, the future for species diversity in the Lake continues to look bleak.