INTROGRESSIVE HYBRIDIZATION OF TILAPIAS IN ZIMBABWE

Three species of tilapia native to Zimbabwe, Oreochromis mossambicus, O. mortimeri and O. macrochir are not naturally sympatric, but because of transplantation they have been brought into sympatry. Allozymes of fish examined from Lakes Kariba, Kyle and Chivero showed evidence of introgressive hybridization. The data showed non-random mating populat ions in Lakes Kariba and Kyle. Aii three reservoirs displayed individu als with intermediate principal component scores and hybrid index scor es indicating hybridization. (C) 1998 The Fisheries Society of the Bri tish Isles.