Selectivity of 40 mm square and 50 mm diamond mesh codends for five species in the Eastern Mediterranean demersal trawl fishery

Abstract

The aim of this study was to determine the selectivity of 40 mm square (40S) and 50 mm diamond (50D) mesh codend for five species, red mullet (Mullus barbatus), annular sea bream (Diplodus annularis), common Pandora (Pagellus erythrinus), axillary sea bream (Pagellus acarne) and blotched picarel (Spicara maena) in the Eastern Mediterranean. Selectivity data were collected by the covered codend method and analyzed. Mean selection curves were analyzed and compared using the between haul variations model for red mullet and annular sea bream. Pooled data were used for common Pandora, axillary sea bream and blotched picarel. In total, 22 valid hauls, 10 with 40S and 12 with 50D codends were carried out. The 50% retention lengths (L₅₀) of 40S and 50D codend were found as 14.5 and 15.3 cm for red mullet, 9.5 and 11.3 cm for annular sea bream, 13.1 and 15.0 cm for common Pandora, 14.4 and 15.3 cm for axillary sea bream, 14.5 and 17.2 cm for blotched picarel, respectively. This study showed that codends with 40S and 50D L₅₀ results improve the selectivity when considering commercially used 40 mm nominal diamond mesh codend in Turkish seas for given species. However, in multi-species, it seems likely that a separation of species system would potentially be of more value than size-selective systems. Therefore, different selective techniques such as grid and separation panel and behaviour of the species against the gear need to be investigated.

Key words: Codend selectivity, 40 mm square mesh, 50 mm diamond mesh, Eastern Mediterranean, demersal trawl.