Appraisal of culture-based fisheries of giant freshwater prawn (Macrobrachium rosenbergii, De Man, 1879) in reservoirs of Sri Lanka

The introduction of high economic value species like giant freshwater prawn (GFWP) makes culture-based fisheries (CBF) a substantial source of income and simultaneously supports the livelihood development of rural fishers in Sri Lanka. However, this CBF strategy has been implemented without any scientific basis, and therefore, this paper evaluated the stocking and production data of GFWP in Sri Lankan reservoirs from 2011 to 2017 to identify interventions for achieving future sustainability. We used two distinct approaches to appraise the CBF strategies practised so far and decrypt the identified shortcomings in the initiatives. The first approach was a straight-head univariate generalized additive model (GAM) analysis of stocking density (SD), production (PRD), recapture efficiency (RCE) and reservoir surface area (A). The latter approach was a hybrid PCoA-GAM for detained data mining for a better management perspective. The relationships among SD, PRD RCE and A were significant and, stochastic PRD and RCE were reasoned by the biased stocking practices identified in the GAM analysis. The hybrid PCoA-GAM is seemingly robust in predicting and explaining the deviances of PRD and RCE of GFWP CBF. Results indicated that the present practices of CBF of GFWP in Sri Lankan reservoirs suffer several weaknesses, overstocking in minor and understocking in both medium and major reservoirs are primarily under consideration, which includes inter alia, the need for effective tools for identification of suitable reservoirs, the inefficient harvesting practices, non-optimal SDs coupled with the possible vulnerability of stocked postlarvae to high mortalities. According to the study, we prefer to set the optimum SD as 1500 PLs ha(-1) to all reservoirs. A comprehensive study has been launched for the enhancement of CBF of GFWP in Sri Lankan reservoirs.