Performance of Macrobrachium rosenbergii in perennial reservoirs: a comparative assessment of fisheries in five perennial reservoirs in the Northern Province of Sri Lanka

The giant freshwater prawn (Macrobrachium rosenbergii), was first introduced to the reservoirs in the Northern Province of Sri Lanka. Studies on the performances of introduced species in reservoirs are essential for development of fisheries and management. The objective of the present study was to evaluate and compare the performance of M. rosenbergii production in five selected perennial reservoirs. Primary data relating to the fisheries of the reservoirs and relevant socio-economic data were gathered through field data collection and questionnaire survey conducted in 2016 and 2017. Unit production of M. rosenbergii in 2017 in the Vavunikulam, Muthayankattu, Puthumurippu, Kalmadu and Muhathankulam reservoirs was 5.3 kg/ha, 3.2 kg/ha, 13.6 kg/ha, 21.8 kg/ha, 12.9 kg/ha, respectively with a farm-gate values of 6.84, 4.39, 2.1, 1.59, and 2.85 million Sri Lankan rupees, respectively. Relative abundance, economic (total farm-gate price) contribution and recapture rate of M. rosenbergii in the catch, ranged between 2.3%-20%, 13.5%-72.3% and 1.44%-6.49%, respectively across the reservoirs. Even though the recapture rate was low, catching of M. rosenbergii improved the livelihood of fishers while increasing their interest in fisheries. Size of the reservoir, stocking density, fishing intensity and gear specification, rainfall, wind and socio-economic factors significantly influenced the catch of M. rosenbergii in the selected reservoirs. The results showed that the introduction of M. rosenbergii as culture-based fisheries in the selected five reservoirs has achieved considerable success, particularly in terms of economic benefits.