Investigation of intra-specific morphological variation of the catfish Pseudarius jella from four estuarine localities in Southern Sri Lanka.

Abstract

Individuals of populations may completely or partially isolate from other populations due to biogeographic barriers such as mountains, rivers, physicochemical barriers etc. resulting variations in phenotypic and genetic characters of the populations. Fish populations particularly show morphological heterogeneity resulted from such isolations. The degree of morphological variation of catfish Pseudarius jella among four estuarine locations along the Southern coast of Sri Lanka was evaluated using selected morphometric and meristic characters. Results of the univariate and multivariate analyses of variance revealed highly significant heterogeneity among the localities. Fish from Nilwala river mouth can easily be separated from other localities (Garanduwa lagoon, Koggala lagoon, Walawa river mouth) by using selected shape variables (head length, head width, body depth, etc.). The morphometric discriminant function correctly classified 56% (average) in to their localities of origin. Morphometric discriminant functions defined regional stocks of Pseudarius jella for further verification of the stock structure. These results of this study revealed that demonstrated of population specific morphological traits among Pseudarius jella from different localities indicating some degree of restriction for inter-population movement. The results were discussed with regard to the possible isolating mechanisms among estuarine populations.