Morphological Heterogeneity in Some Estuarine Populations of the Catfish Arius Jella (ariidae) in Sri Lanka

Intra-specific morphological variation in the indigenous catfish Arius jella (Ariidae) was studied in five estuarine localities in Sri Lanka (Koggala lagoon, Walawe estuary, Garanduwa lagoon, Nilwala estuary and Chilaw lagoon) using morphometric analysis. Five morphometric characteristics describing the shape of the fish were significantly different among some of the locations. Significantly shorter pre-orbital length (8.3% SL vs 9.2-10.7% SL in the other populations) in specimens from Walawe estuary is a populationspecific character. Significant differences in other characteristics were found indicating heterogeneity in morphology. The first two canonical variates (CV) explained 82.7% of the total variation in the data, yet the plot of the CV failed to display significant separation of the sample populations. Derived classification functions could correctly classify an average of less than 50% individuals into their a priori groups. There was no agreement on the isolation by distance model. The results indicate a small degree of spatial separation in morphology in A. jella among the studied estuarine localities.