Community Diversity and Dynamics of Fish Assemblages in Lake Kanyaboli, Western Kenya

Although Lake Kanyaboli provides a sanctuary for fish species that are considered extinct (e.g., Oreochromis esculentus, Oreochromis variabilis and Haplochromis spp.) in Lake Victoria, comprehensive data on species diversity and abundance are lacking. This study, conducted over a year (February 2020 to February 2021), addressed this gap by assessing the temporal variation in fish diversity, abundance and catch (biomass) in Lake Kanyaboli. The primary fish data collected in the lake were supplemented with secondary data, and physico-chemical variables were used to correlate with fish assemblages. Fish catches decreased over time from 1981 to 2020, with the highest catch observed in 1981 (250 mt). Fish species composition data showed heterogeneity over the years, ranging from 9 to 15 species. O. esculentus, haplochromines, Oreochromis niloticus, Protopterus aethiopicus and Clarias sp. were present in all the reviewed years (from 1981 to 2020), whereas Coptodon zillii was non-existent post-1981 results. The February 2020 to February 2021 survey recorded 14 species dominated by Cichlidae (10 species), whereas Protopteridae and Anabantidae recorded one taxon each. Interestingly, Bagrus sp. was recorded in the current study, suggesting fish movement from the Yala River to the lake. The annual fish catch in the lake comprised tilapias (50%, O. esculentus, O. variabilis, O. niloticus and Oreochromis leucostictus), Clarias sp. (23%), P. aethiopicus (20%), haplochromines (7%), Cyprinids (0.03%) and Anabantidae (0.01%). There were no significant monthly differences in fish abundance and fish catches. The decline in fish catch in Lake Kanyaboli over the years is consistent with most tropical lakes and reservoirs in developing countries due to overexploitation. This study highlights the need for biomonitoring in Lake Kanyaboli to protect its fish population, including the endangered O. esculentus and O. variabilis, and ensure the long-term sustainability of the ecosystem.