Lake Naivasha (Kenya,East Africa) fishery and its management together with a note on the food habits of fishes

The Lake Naivasha fishery is constituted by three introduced species, Sarotherodon leucostictus, Tilapia zillii and Micropterus salmoides. No indigenous species are now found in the lake. S. spilurus niger, another introduced species, and hybrids of S. s. niger × S. leucostictus, abundant in 1961, have almost completely disappeared.The annual catch of Sarotherodon-Tilapia and M. salmoides between 1968 and 1974 ranged from 109·2 to 1479·6 metric tons and 7·9 to 471·9 metric tons respectively.S. leucostictus is a bottom feeder (chironomid larvae 64°24%, detritus 20·58%), T. zillii feeds on aquatic macrophytes (76·62%) and M. salmoides feeds almost exclusively on crayfish (78·25%). A major portion of the fish food present in the lake is left unused.The yield, which has progressively declined since 1968, could be increased considerably by introducing certain management measures. These are discussed.