Distribution and abundance of unexploited fish species in three Sri Lankan reservoirs

Abstract

In the reservoirs of Sri Lanka, two exotic cichlid species, Oreochromis mossambicus and O. niloticus are dominant. Small indigenous cyprinid species are abundant in reservoir fish communities, but they remain unexploited due to poor consumer preference. In the present paper, an attempt is made to investigate the spatial and temporal fluctuations of distribution of these unexploited small indigenous cyprinid species in three reservoirs of Sri Lanka. Experimental fishing with multi-mesh gillnets (12.5 mm to 37 mm stretched mesh) having the spread height of 1.5 m, was carried out in inshore and offshore areas of the three reservoirs during the seasons of high and low water levels. As cichlids exhibit depth preference with size, their juveniles were not caught in these gillnets which were set in offshore areas with depths greater than 1.5 m. Amblypharyngodon melettinus, Puntius chola and P. filamentosus were found to be the most abundant species in all three reservoirs. The species composition in the gillnet catches appears to be influenced by water level fluctuations in reservoirs perhaps due to inshore-offshore migration of individual fish species associated with water level fluctuations. Despite the site-specific differences in species distribution and abundance and their temporal variations, a small mesh (12.5 mm to 37 mm) gillnet fishery with the minimum panel height of 1.5 m can be introduced to exploit small indigenous cyprinids in Sri Lankan reservoirs without harming the existing fishery of exotic cichlids.