Southern Aegean Sea Trawl Fishery; Discard Ratio and Mortality of Targeted Species

Abstract

This study was conducted between March 2019 and February 2020 in Güllük Bay, southern Aegean Sea. The aim of the study was to determine the fishing mortality rates besides, commercial and discard ratio of Aegean Sea trawl fishery. Samples were obtained from a commercial trawl ship in every month in open season. Length–weight relationships (LWRs) of some discard species, fishing mortality rates of targeted species (Mullus barbatus barbatus (Linnaeus, 1758), Pagellus erythrinus (Linnaeus, 1758)) and discard ratio were determined. Totally, 113 discard species were captured and discard ratios by weight were varied between 36.9% and 63.3% and mean discard ratio was 50.8%. According to minimum landing size (MLS) of targeted species M.barbatus barbatus and P.erythrinus, 82.6% of M.barbatus barbatus and 97.7% P.erythrinus were below MLS in discard. Current fishing mortality (F) of M.barbatus barbatus and P.erythrinus are seriously higher than Fopt and Flim reference points Current exploitation rates (E) of M.barbatus barbatus and P.erythrinus is higher than optimum exploitation rate. Fishing mortality of targeted species should be decreased around safety limits to ensure sustainability. In order to minimize the discard ratio, technical regulations such as using larger mesh sizes are needed to decrease in fishing mortality. Seasonal closure dates for trawl fishery are different in Aegean (15 April-31 August) and Mediterranean (15 April-15 September). This 15 days gap in Mediterranean causes fleet (Mediterranean trawlers) shift to Aegean trawl areas. Therefore, seasonal closure dates should be organized to prevent fishing pressure on Aegean trawl fishing areas. Stock related and discard reduction studies on trawl fishery are needed in Aegean Sea