Abstract:
Three species of tilapia viz; Oreochromis mossambicus, Oreochromis niloticus and Tilapia rendalli, are well
established 5a Sri Laaka and significant ia fresh water fishery. Introgressive hybridisation is common
between certain tilapia species producing hybrids that can obscure the morphologicafboundaries between
species and also have numerous negative effects on long-term fishery. Therefore an easy index for
identification of tilapia species and their hybrids in the field, which is based on morphometry of tilapia fish
is essential. However, such a morphological index substantiated by DNA based study is not available. The
present investigation reports the most important morphometric characters for the identification of tilapia
species in Sri Lanka. The maternal origin of selected individuals of such groups was determined using
heteroduplex formation of PCR products of a part of control region of mitochondrial DNA (mtDNA) with
the PCR product of the same region of an authentic O. mossambicus. The majority of individuals tested had
maternal origin conforming to the present morphologically defined species, whereas a few (03) O. niloticus
individuals had mossambicus maternal origin indicating hybridisation.
