Selectivity of 50 mm T0 and T90 codends for commercial shrimp species in the Turkish deepwater trawl fishery, Eastern Mediterranean

Abstract

The study compared the selectivity of 50 mm mesh size conventional (T0) and 90° turned mesh (T90) demersal trawl codends for four commercial shrimp species (Aristaeomorpha foliacea, Aristeus antennatus, Parapenaeus longirostris and Plesionika martia) in the Bay of Antalya in the eastern Mediterranean. Data were collected from 27 valid hauls using the covered codend method. Selectivity parameters were obtained using the logistic equation with the maximum likelihood method and by taking into account the between-haul variations. Results show that changing the codends from T0 to T90 increases the percentage of escapees for all four targeted shrimp species. According to species, a change in the mesh configuration significantly increases L50 by 7–14%. However, for the two commercially important red shrimp species (Aristaeomorpha foliacea and Aristeus antennatus), even the L50 values obtained in the T90 codend (23.3 mm) remain rather low for the release of sufficient numbers of immature specimens. First maturity sizes (FMS) for these two species are 38 and 30 mm, respectively; therefore, for their sustainable exploitation, additional management measures must be investigated including larger mesh sizes.