An analysis of species changes in Lake Victoria: did the Nile perch act alone?

Abstract

The introduction of Nile perch, Lates niloticus, to Lake Victoria in the late 1950s has incited much controversy and discussion, primarily because of the subsequent dramatic loss in species diversity and abundance of a unique haplochromine group (Barel et al., 1985, 1991; Coulter et al., 1986; Payne, 1987; Ribbink, 1987; Bruton, 1990; Witte et al., 1992a,b). Four species of tilapias were also introduced, the Nile tilapia, Oreochromis niloticus, successfully. For 20 years, while traditional fish catches continued to decline, catches of Nile perch were minimal. Then in the early 1980s the Nile perch population boomed and by 1990 the total annual catch from Lake Victoria had increased fivefold, to over 500 000 t (tonnes) (Fig. 7.1). The lake now supports a thriving fishery and supporting industries (Reynolds and Greboval, 1988; Greboval, 1990; Chapter 10). Catches of traditional species have further decreased and the fishery now largely comprises three species: the total demersal exotics, Nile perch and Nile tilapia and a native zooplanktivorous, pelagic cyprinid, Rastrineobola argentea, the dagaa or omena (Chapters 2–11).