The Consequences of Anthropogenic Stressors on Cichlid Fish Communities: Revisiting Lakes Victoria, Kyoga, and Nabugabo

Lakes Victoria, Kyoga, and Nabugabo (“the Lake Victoria region”) are remarkable for hosting one of the largest assemblages of cichlid fishes among the African inland lakes. Here, we review the role and severity of anthropogenic and environmental stressors on the cichlid communities in the Lake Victoria region to understand the mechanisms leading to the persistence and resurgence of some of the cichlid fishes. Our review suggests that (1) the native Oreochromis species populations primarily collapsed due to overfishing and that the introduced species and habitat change suppressed their ability to recover; (2) without primary triggers associated with change in the environment and habitat conditions, particularly eutrophication and associated anoxia and reduced water transparency, Nile perch (Lates niloticus) predation alone may not have caused the massive loss of species diversity; and (3) the resurgence of haplochromine cichlids is due to a combination of general improvement in the environment and reduction in L. niloticus abundance, with additionally possibly some rapid ecological adaptations. We conclude that environmental stressors will likely continue to shape the ecosystems in which the remaining endemic cichlid fish diversity continue to evolve, clearly involving genetic exchange between species. If water clarity can be improved again, it is possible to maintain a diverse assemblage of endemic species.