Abstract

The ecological structure and functional proceses of fish assemblages in the 26 square kilometer man-made Periyar Lake in Periyar Tiger Reserve (PTR) and 75 Km long streams (Periyar and Mullayar) were studied during 1994-96 . A total of 27 fish species were encountered in the system. Of these 14 (52) are endemic to Western Ghats, 52 are threatened and 33 are endemic and/or threatened. The diet and morphological analysis reveal that the fishes largely depend on food bases like aquatic and terrestrial insects and other benthic macroinvertebrates with distinct trophic segregation patters. Based on diet, the fishes are calssified into groups by hierarchical clustering technique namely, terrestrial insectivore, benthic insectivore, insectivore-omnivore, insectivore- detritivore, omnivore and algivore. Similarly, on morphological characteristics, the fishes are grouped into water colomn rovers, bottom clingers, deep-bodied rovers, bottom eel-likes and surface-orienters. Biological invasion by exotic fishes like (Oreochromis mossambicus and Cyprinus carpiocommunis, analysed with ecological tools like diet, morphologic as well as habitat overlaps indicate the existence of a high degree of interspecific interaction between these exotic fishes and a few native, endemic and/or threatened fishes. The average daily fish catch per fisherman is estimated to be 4.2 kg, which realised an amount of Rs.168.00 per fisherman per day