Effects of traditional and alternative mesh sizes in trammel nets on selectivity and catchability of Penaeus kerathurus (Forskål, 1775) in the Marmara Sea

Abstract

Penaeus kerathurus is one target species caught with trammel nets by small-scale fishers in the Marmara Sea. Generally, 40 mm mesh size is used in trammel nets. In the present study, alternative mesh sizes (36 mm, 44 mm) were compared with the 40 mm traditional mesh size for their effects on selectivity and catchability. A total of 27 species comprising 3777 individuals and weighing 123615 g were caught. Penaeus kerathurus constituted 72.4 % of the total number of individuals and 58.3 % of the total weight. The mean (±Ss) catch-per-unit-of-effort (CPUE) for the 40 mm mesh size for commercial fishers was determined to be 7.73±4.99 g/m.operation⁻¹, and 9.92±4.47 g/m.operation⁻¹ for the present study. The CPUE values for the 36 mm and 44 mm alternative mesh sizes were determined as 4.83±2.67 and 7.77±4.92 g/m.operation⁻¹, respectively. The highest CPUE value for individuals was detected with the 40 mm mesh size. The mean carapace length, total length and total weight of P. kerathurus significantly increased with mesh size. The model lengths of P. kerathurus were found to be larger than the carapace length at first sexual maturity in the Marmara Sea. So, traditional and alternative mesh sizes can be used to catch P. kerathurus. As a result, P. kerathurus fisheries in the Marmara Sea were described for the first time. Alternative mesh sizes did not significantly affect catch and bycatch composition, selectivity, but they decreased catching efficiency. New and additional modifications, innovations or changes can be made to trammel nets to promote sustainable P. kerathurus fisheries.