Ecological changes in Lake Victoria after the invasion of Nile perch (Lates Niloticus): the catchment, waters quality and fisheries management
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Lake Victoria, the second largest lake in the world, has undergone successive dramatic changes since 1920's. Intensive non-selective fisheries, extreme changes in the drainage basin of vegetation, industrialization, agricultural developments, dams, introduction and invasion of exotic fish species that led to the destruction of the native and endemic components followed by a progressive build-up of physical and chemical changes in Lake Victoria have identified substantial increases in chlorophyll concentration and primary productivity as well as decreases in silica compared to values measured 30 years ago. Present sulphate concentration (0.1 mg/L) are lower than the lowest values reported from other large lakes in the world. There has been a shift in the phytoplankton community towards dominance of blue-greens. The zooplankton densities are relatively low and the body sizes of the organisms are small. Anoxic waters have recently been found at shallower depths than previously reported in the lake suggesting significant increases of oxygen demand in the seasonally formed hypolimnion. Algal blooms have also been enhanced in the lake. Fisheries management has led to a shift in the fishery from a multi-species (400-500 fishes including haplochromids) to only two major exotic species Lates niloticus and Oreochromis niloticus and the endemic species Rastrineobola argentea. The present practices of lake management have not resulted in the improvement of water quality.
- Conference Papers