Life history patterns of some selected endemic freshwater fish species inhabiting two major river basins of Sri Lanka

Life history information on six endemic fish species namely Belontia signata, Pethiya cumingii, P. nigrofasciata, Puntius titteya, Rasboroides vaterifloris and Garra ceylonensis inhabiting the Kalu Ganga and Kelani Ganga river basins in Sri Lanka was evaluated. The growth constant of the fish species showed a positive relationship with the river order where they inhabited. The length at 50% maturity (L_m) significantly correlated with the asymptotic length and growth constant indicating that fishes with slow growth become sexually mature late in their life cycles. The optimal lengths for sustainable exploitation of the fish species studied were significantly (p<0.01) correlated with asymptotic lengths and lengths at 50% maturity whereas negatively correlated with natural mortality. This analysis indicated that L_m was a foremost function of size of fish apart from maximum length observed (L_max,) and that L_m and L_max can be used as deterministic variables for quantifying optimal size of exploitation for sustainability and conservation of fish populations.