Fleet optimization of trawl fishery along southwest coast of India using surplus production model

Abstract

The impact of trawl fisheries on the multi-species fishery resources, along the southwest coast of India, was studied by applying surplus production model and genetic algorithm approach using 23 years of time series data on catch and fishing effort during the period 1990-2012. The annual trawl landings varied from 0.282 million tonnes (t) in 1990 to 0.570 million t in 2012 with average annual landing of 0.357 million t. Though the effort in number of fishing units has been reduced from 0.756 million units in 1990 to 0.408 million in 2012, the effort in actual fishing hours has increased substantially (142%) during the last two decades. The catch rate of high value groups such as large pelagics, penaeid prawns and cephalopods have gradually declined whereas low value groups such as small pelagics and miscellaneous groups have been caught in higher rate. The average biomass, yield, fishing mortality and fishing effort of the resources harvested by trawlers during the last three years were compared with the maximum sustainable yield (MSY), biomass at MSY level (BMSY), fishing mortality at MSY level (FMSY) and fishing effort corresponding to MSY (fMSY), which are estimated using genetic algorithm approach based on Schaefer’s non-linear surplus production model. Assuming the last three years fishing effort as the current level of effort, the optimum level of exploitation was found marginally lower (99%) than the current level of exploitation to keep the annual average yields just below MSY.