GENETIC AFFINITIES OF AN INTRODUCED PREDATOR - NILE PERCH IN LAKE VICTORIA, EAST-AFRICA

Although the introduction of Nile perch, Lates niloticus, to Lake Vict oria has received intense global attention, especially in relation to its impact on endemic cichlid species and on fishery yields, fundament al information on its taxonomy and population genetics is larking. Mos t importantly, the introduced fish originated from two lakes (Lakes Al bert and Turkana) containing three Lates species, and it has never bee n entirely clear which of these became established in Lake Victoria, o r indeed whether the Lake Victoria population is derived from hybridiz ation between Lates species. In addition, genetic drift caused by the relatively small founder population (approximate to 400), the initiall y slow population increase followed by a period of explosive populatio n growth, and selection pressures in the new environment may have resu lted in substantial genetic changes. Allozyme data indicated that the introduced Nile perch of Lake Victoria were mainly L. niloticus from L ake Albert, although maximum likelihood estimates of stock contributio ns (GSI) suggested the presence of L. macrophthalmus. In contrast, int roduced Nile perch in adjacent smaller lakes (Lakes Kyoga and Nabugabo ) appeared to be entirely L. niloticus. The effect of the introduction s on allozyme diversity varied among lakes and appeared to be uncorrel ated to the number of fish introduced.