Variations and changes in habitat, productivity, composition of aquatic biota and fisheries of the Kyoga lake system: lessons for management

The Kyoga lake system, which is c. 4 m deep, originally had a diverse fish fauna, extensive macrophytes and wetlands. Most (82%) of its water comes from Lake Victoria, is controlled through three dams and has a short residence time of c. 3 months. Physical and chemical factors, plankton productivity and composition vary across the lake from east to west. The macrophyte cover decreased after the heavy El Niño rains of 1961, and the area of wetlands decreased by 48.5% between 1994 and 2008 mainly because of their conversion to agriculture. The main lake was infested with water hyacinth in the 1990s but subsequently this was brought under control. The native fishes were overexploited and non-native fishes, including a top piscivore, Nile perch Lates niloticus L., were introduced and boosted fish production, but they also were overexploited. Nile perch also preyed upon and decimated native species, which survived only in satellite lakes. Populations of some of these species recently have started to recover in the main lake. Efforts should be made to control habitat loss and water-level fluctuations, wetland loss, overexploitation of the fishes, conserve the surviving fish species and address the emerging challenge of climate change.