Introductions of exotic fish species in tropical freshwaters: Purposes and consequences.

European emigrants introduced several fish species into tropical freshwater ecosystems for the purpose of sport fisheries. At present, the main goals of introductions are the management of small-scale fisheries, and aquaculture. The introduction of clupeid pelagic species into natural or artificial lakes was an economic success, because it allowed an improvement of the local fisheries while no adverse impacts on the indigenous fauna were reported. On the contrary, the introduction of large predators has had dramatic consequences on the native fauna. This was the case for trout (Salmo trutta Linnaeus, 1758) in Australia or Lake Titicaca, and the Nile-perch (Lates niloticus Linnaeus, 1758) in Lake Victoria. Tilaplines may be beneficial to the ecosystem and local fisheries when introduced into depauperated systems, while in systems with greater species richness, the disappearance of fish species following the introduction of cichlids was reported. Madagascar lakes provide good examples of the impact of successive introductions of various fish species on native fish assemblages and fisheries.