Distribution of fishes along the Sondu‐Miriu River of Lake Victoria, Kenya with special reference to upstream migration, biology and yield

摘要

AbstractA descriptive account of the fisheries in the lower Sondu‐Miriu River of the Lake Victoria catchment before the construction of a hydroelectric dam is presented. It can support an annual yield of 81‐5‐1081 and a catch rate of 11.4kg/ha/h. Out of the 28 species present in the river, the most abundant wereClarias gariepinus(Butchell),Schilbe mystus(L.),Synodontis afrofischeri(Hilgend),Oreochromis variabilis(Boulenger),O. leucostictus(Trewavas), andLates niloticus(L.),Micropterus salmoides(Lacepède) andL. niloticusare a new development in the river fishery introduced respectively from the highland areas and Lake Victoria. The yield in the river has been reduced from 668t in 1959 to the current 108t and species available replaced the once abundantBarbus altianalis(Boulenger) andLabeo victorianus(Boulenger). This drastic reduction in yield can be attributed to overfishing, habitat degradation and poor management. The upstream migration of the river fishes extends as far as 10km from the Lake Victoria river‐mouth. The period of peak reproductive activity (March‐June and October‐November) coincides with the established rainy seasons in the region. The top ranking food items of the fishes are terrestrial and aquatic insects, vegetable matter, detritus, crustaceans, molluscs, fish, plankton and grit. The endemic fish stock appears to be in a depressed state, showing signs of overexploitation, and therefore careful stocking programmes to restore the fish balance would be appropriate. Fishing effort in the river should be regulated by licensing of nets and the minimum size of fish landed should be regulated through cooperative societies, clans, party elders and other social o