Evaluating the fishery of tropical reservoirs using surplus production models: A case study of Aliyar Reservoir, Tamil Nadu, India

Reservoir fisheries support the livelihood needs of socio-economically deprived fishers and ensure the nutritional security of rural populations. To sustain community food safety and economic needs, a basic understanding of the prevailing biological and economic conditions, as well as a comprehensive evaluation of the fishery is essential. To this end, the present study focused on evaluating the fisheries of the small Aliyar Reservoir located in the Coimbatore District of the state of Tamil Nadu, India, utilizing surplus production models. The maximum recorded fish catch was 51.3 MT in 2015, with the minimum catch of 10.89 MT obtained in 1991, and the average production during 1985 to 2018 being 30.80 MT from the reservoir. The peak catch season was during the months of February to May. The MSY (Maximum Sustainable Yield) and other key fish population parameters, including the carrying capacity (K), catchability coefficient (q), intrinsic population growth rate (r) and coefficient of variation (CV), using catch and effort data (CEDA) analysis and ASPIC (a surplus production model incorporating covariates) computer software packages. Using CEDA software, the estimated MSY was 36.92 MT (CV = 0.47) using the Fox model and 36.68 MT (CV = 0.307) using the Schaefer model. An integrated surplus production model (CYP) of Clarke et al. (Marine Research Economics, 1992, 7, 115) was also fitted to the data and found to be the best fit with the MSY, an estimated optimum effort of 51.20 MT and 5110 nets/year. The results indicated the need for increasing the fishing effort with appropriate standard gears for exploiting the fish stock. Further economic optimization with the CYP model indicates increasing the fishing effort by 34% will lead to a 40% increase in the annual profits for the fishermen.