AdultBagrus docmacin the Nyanza Gulf of Lake Victoria feeds mostly on fish–Haplochromisspp. andEngraulicypris argenteus(Pelligrin). Juveniles prefer aquatic benthic invertebrates withPhyllogomphus aethiop.?(K.elys),Phanostoma senegalense(Brauer), Chironomusspp. andCaridina nilotica(Roux) dominating, followed byChaoborusspp.,Povilla adusla(Navas),Valvataspp. andNeoperla spio(Newman) in order of importance.B. docmacexhibits diurnal changes in feeding habits. It feeds actively during dusk and dawn, taking advantage of the twilight environment for successful feeding mission–a crespuscular feeding behaviour. Selectivity of food seems dependent on occurrence of prey items. The species has an ubiquitous distribution in the Gulf but occurs more frequently with increasing water depth and decreasing water temperature. The biomass of the predator shows little correlation with water conductivity.Bagrus docmacand the other important piscivorous species in the lake,Lates niloticus(L.), are mutually exclusive in their bathymetric distribution within the Gulf. They also have different preferences for water temperature and conductiv