Relative growth of invasive and indigenous tilapiine cichlid fishes in Tanzania

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 over native species. Here we compared the relative growth rate of sympatric populations of introduced Oreochromis niloticus (Nile tilapia) to indigenous Oreochromis jipe (Jipe tilapia) at three impoundments in Northern Tanzania. Using scale increments as a proxy for growth, we found that O. niloticus had an elevated growth rate relative to O. jipe , with the greatest O. niloticus growth rates being evident in the Nyumba ya Mungu reservoir. These results help explain why O. niloticus may be a superior competitor to native species in some circumstances. However, further introductions of this non-native species should be undertaken with caution given potential for negative ecological impacts on threatened indigenous tilapia species.