Biochemical genetic markers to identify hybrids between the endemic Oreochromis mossambicus and the alien species, O-niloticus (Pisces : Cichlidae)

The invasion of exotic Oreochromis niloticus into the Limpopo River system( in the vicinity of the the Vembe Nature Reserve, Northern Province, South A frica) was studied. Oreochromis niloticus was found in pools in the nearly dry river bed, as well as in dams alongside the river. Pure O. mossambicus was also Found at these localities, as well as individuals that appeared hy brid-like. Starch gel-electrophoresis of muscle tissues and the resolution of protein loci using specific histochemical techniques identified the pure species as well as verifying the presence of hybrids. Various morphologica l characteristics were studied in order to identify hybrids. Red tilapias f rom the aquariums at the Rand Afrikaans University were also analysed to de termine if they are hybrids or mutants. This is the first account of hybrid s between the above-mentioned species in South Africa and there is no evide nce that the red tilapias are hybrids.