Population dynamics and life-history styles of Nile tilapia,Oreochromis niloticus,in Ferguson's Gulf,Lake Turkana,Kenya

Synopsis Three observed dynamic aspects of the Nile tilapia population around Ferguson's Gulf at Lake Turkana, Kenya are evaluated and discussed: the seasonality in catch rates, the enormous inter-annual abundance variations, and the large changes in median size at first maturity. A clear understanding of the regulating mechanisms behind these features has never been achieved, although seasonal changes in the hydrology of shallow sheltered refuges seems to play an important role. This paper suggests a further holistic approach taking the impacts and interrelationships of both the primary productivity and the various predators into account. A synthesizing ecological hypothesis is elaborated, which concludes that most observations on the tilapia dynamics can be explained from changes in the oxygen concentrations and size-specific mortality pressures. Variations in these two proximate factors can ultimately be explained by the floodplain-type fluctuations in the Ferguson's Gulf environment.