Feeding interaction of exotic Oreochromis niloticus (Linnaeus, 1758) versus native Coptodon rendalli (Boulenger, 1896) in the upper Kabompo River, northwest of Zambia.

Abstract

Evaluating the feeding interaction of fishes is fundamental in understanding the impacts of introduced species on the community structure and ecosystem function of native species. In the Zambian Rivers, studies have shown that native species has been impacted upon by exotic Oreochromis niloticus, but few studies have investigated feeding interactions between exotic Oreochromis niloticus which is omnivorous and aquaculture preferred herbivorous native species (Coptodon rendalli) in the natural distribution. We analysed the stomach contents of 368 specimens of the fishes to examine the feeding interactions between O. niloticus and C. rendalli in the upper Kabompo River, northwest of Zambia. Both species were grouped into size classes of <50, 51−100 and 101−150 mm total length (TL). However, in the size classes 51-100 mm and 151-100 mm O. niloticus had a larger dietary niche because of its generalist diet than the native species, whose diet mainly comprised of diatoms and algae. There was no significant ontogenetic diet shift for both species, except for O. niloticus in size class 101-150 mm, whose diet consisted mainly of zooplanktons and micro fauna. The results showed an interspecific competition in their size classes, except for 101-150 mm size class, that indicated low dietary overlap. This poses major impacts on food web structure and may explain population decreases of some native species in the upper Kabompo River. Future studies are required to further understand feeding interaction between the exotic and other native fishes in the Kabompo River and other rivers across African where the species coexist.