Relative growth of invasive and indigenous tilapiine cichlid fish in Tanzania

Abstract

Non-native species have been widely distributed across Africa for the enhancement of capture fisheries, but it can be unclear what benefits in terms of fisheries production the non-native species bring, compared with native species. Here we compared the relative growth rate of sympatric populations of non-native Oreochromis niloticus (Nile tilapia) to native Oreochromis jipe (Jipe tilapia) in three waterbodies in northern Tanzania. Using scale increments as a proxy for growth, we found that O. niloticus had a high growth rate relative to O. jipe, with the highest growth rates for O. niloticus being observed in the Nyumba ya Mungu reservoir. These results help to explain why O. niloticus could be a superior competitor to native species in some circumstances. However, more introductions of this non-native species should be undertaken with caution given potential for negative ecological impacts on threatened indigenous tilapia species.