Trophic shifts in predatory catfishes following the introduction of Nile perch into Lake Victoria

Abstract

This study looked for evidence of trophic shifts in the diet of two predatory catfishes (Bagrus docmac and Schilbe intermedius) following the establishment of introduced Nile perch (Lates niloticus) into lakes of the Lake Victoria basin. Bagrus docmac exhibited a shift from a primarily piscivorous diet dominated by haplochromine cichlids to a broader diet that included a significant proportion of invertebrates and the cyprinid fish, Rastrineobola argentea, which became abundant following depletion of the haplochromines. Schilbe intermedius exhibited a trophic shift from a piscivorous diet dominated by haplochromines to an insectivorous diet. The flexibility in diet exhibited by these two catfishes may have permitted these species to persist, albeit in reduced numbers, subsequent to the introduction of Nile perch and may facilitate resurgence as fishing pressure reduces numbers of large Nile perch.