Abstract:

Ngege?Oreochromis esciHam??
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:egion (LVR)
fisheries. Together with its indigenous congener O. variabilis^ it was dispkiccd from Lakes Victoria
and Kyoga of LVR and was found to wr?as
minor lakes and reservoirs around the tvvo lakes.
! q :
tilapiines was thought to be principally driven by ciuuiged hike
?.wilhin the peripheral
:.:)LVR indigenous
and predation by the
introduced Nile perch, but also competition and genetic swamping by ihe closely related introduced
and comparatively more ecologically versatile tiiapine species. In a study carried out in the LVR
between 1993 and 2003, micrc satellites and RAPD markers were used to analyse the remnant
populations so as to establish the population structure and extant genetic diversity of O. esculentus.
Analyses indicated that the surviving O. esculentus retained a high proportion of genetic diversity
with high differentiation between units an indication of genetic exchange behvecn indigenous
and introduced Nile tilapia where the hvo forms co-existcd. While this heightened concern for
genetic swamping of the remnant population units by the introduced tilapiines it was noteworthy
that in a few of the satellite lakes where the O. esculentus was dominant evidence for introgression
was weak