Increasing dominance of Nile tilapia, Oreochromis niloticus (L) in Lake Victoria, Kenya: Consequences for the Nile perch Lates niloticus (L) fishery

Nile tilapia, Oreochromis niloticus and Nile perch, Lates niloticus were introduced into Lake Victoria in the 1950s and 1960s. The former was to boost the then declining tilapiine fishery, while the latter was to convert the abundant bony haplochromines to fish flesh. Fish samples were collected by bottom trawling from 1998 to 2000 and in 2004 to 2005 from the Kenya waters of Lake Victoria. The goal was to evaluate the current population characteristics and ecology of the species. Length frequency distribution and size at maturity of Nile tilapia depicted a stable population with high proportions (30%) of mature fish, unlike Nile perch where more than 98% of the individuals were immature. Nile tilapia previously distributed in 25% in 2005; while Nile perch declined from 95% in 1990s to 58% in 2005. The increase in Nile tilapia catches and its spread into deeper waters is attributed to declining...