Abstract
Present study was carried out to assess the abundance and diversity of fin-fish and prawn species in the selected five reservoirs in the Northern Province, Sri Lanka. Fin-fish and prawns caught by multi-mesh gillnets, and rod and hooks, were sampled from January to December 2017. Relative abundance and diversity indices were calculated and, differences and similarities among reservoirs in different months were assessed. The hierarchical clustering was used in constructing dendrogram. Of the 27 finfish species and two freshwater prawn species identified in total, the highest number of species were observed in Muthayankattu reservoir (26 species) while Puthumurippu reservoir had the lowest (14 species). Oreochromis niloticus was the dominant species in all the reservoirs. Small reservoirs (Puthumurippu, Kalmadu and Muhathankulam) showed high Shannon-Weiner diversity index and evenness, though low in dominance index, compared to large reservoirs (Vavunikulam and Muthayankattu). Selective harvest methods, number of fishers and seasonal variation of hydro-climatic factors such as rainfall, strong wind and water level significantly influenced the diversity of fish species. Increasing fishing pressure and use of destructive fishing methods during low water level were the main contributors for diversity loss in the five perennial reservoirs studied.