Morphological variation of four tilapia populations in selected reservoirs in Sri Lanka.

Morphological variation among three populations of introduced Tilapia fish collected from Kurunegala, Anuradhapura and Polonnaruwa and the brood stock of Nile tilapia (Oreochromis niloticus) collected from the Udawalawe tilapia breeding centre was investigated by multivariate analysis of twenty morphometric and fourteen meristic characters. Discriminant analysis and cluster analysis of conventional morphometric measures showed a high divergence among the populations while the conventional meristic measures did not show a divergence among the populations. These results showed that the tested fish samples could be grouped into its respective collection site based on the morphometric characters. The morphometric differences between the populations may have appeared due to either genetic differences or environmental factors. The thirty-four characters, extracted from stepwise discriminant analysis played important roles in morphological differentiation.Tropical Agricultural Research Vol. 23 (2): 105 – 116 (2012)