Fisheries Resources Department, P.O. Box 4, Entebbe, Uganda

Status of selected fish taxa in relation to conservation of their genetic and species diversity in the Victoria and Kyoga basin lakes

With the dramatic changes in Lake Victoria and Lake Kyoga's basin, fish species are adversely affected through ecological marginalisation and subsequent genetic drift and other related consequences. We report on studies that are aimed at establishing the ecological and genetic status of selected major fish taxa in the two lake basins. Studies included analysis of the genetic status of haplochromine assemblage, the tilapiine forms (both native and introduced species) and, the Labeine (Labeo victorianus-Ningu). The introduced species are the most ecologically dominant and more genetically diverse among the tilapiines. The two native tilapiine species were found to be displaced out of the two main lakes and were extant only in a few of the surrounding satellite lakes, in marginal population sizes. Most haplochromine forms found in the satellite lakes were relics or equivalent forms of what is feared as extinct or endangered forms in the two main lakes. However, the two main lakes still contain a relatively high genetic diversity and represent viable populations for conservation efforts. The Ningu populations are highly genetically diverse and subdivided along units. This situation may be due to either severe reduction in population sizes, or natal fidelity to the different adjoining streams of the two lakes. We propose conservation measures in the two lake basins that will enhance the survival and evolutionary viability of the remnant populations in the changed environment.