Maximum economic and sustainable yields in perennial reservoir fisheries of Sri Lanka: insights into stocking practices and fishing intensity for multi-species management

Abstract

This study explores the maximum economic and sustainable yields in perennial reservoir fisheries in Sri Lanka, focusing on the multi-species management of carp, tilapia and FWP stocks. By analysing data from 18 irrigation reservoirs where CBF are conducted, we examine the relationships between fishing intensity, stocking density and economic outcomes. Our findings indicate that fishing intensity and stocking practices significantly influence fish yields and economic returns. The relationship between fishing effort and yield for carp species follows a second-order curve, suggesting optimal fishing pressures for carp species. For carp, the maximum sustainable yield was found at 226 kg ha-1 yr-1 at an optimal fishing intensity of 55 boats ha-1 yr-1, having a maximum economic return (MER) of LKR16,000 ha-1 yr-1 for LKR2,600 ha-1 yr-1. However, the FWP fishery did not show a significant relationship between fishing effort and yield, likely due to the incidental nature of prawn harvesting. The study reveals that tilapia’s self-recruiting ability results in lower stocking costs and higher profitability compared to carp. By analysing the cost-effort and cost-stocking relationships, we highlight the importance of strategic investment in stocking and fishing practices to maximise returns without overcapitalisation. This study contributes valuable insights into the sustainable management of multi-species reservoir fisheries, emphasising the need for species-specific approaches to optimise both economic and ecological outcomes. Future research should further refine these models and incorporate socioeconomic factors for more adaptive and efficient management strategies.