Effect of Codend Circumference on the Size Selection of Square-Mesh Codends in Trawl Fisheries

摘要

It is well established that increasing mesh number in the circumference of a diamond-meshtrawl codend can reduce size selection for round fish, whereas selection for flat fish speciesis unaffected. This effect has also been documented in Mediterranean trawl fisheries. Incontrast, no information is available with regard to the effect of increasing mesh number inthe circumference of square-mesh codends on the size selection of round fish and flat fishspecies. A field study was devised to bridge this gap and formulate proposals aimed atimproving trawl fishery management. Size selection data were collected for a round fishspecies, red mullet (Mullus barbatus), and two flat fish species, Mediterranean scaldfish(Arnoglossus laterna) and solenette (Buglossidium luteum). Fishing trials were conductedin the Adriatic Sea (Central Mediterranean) using three square-mesh codends that differedonly in mesh number around the circumference. Results demonstrated that increasing thenumber of meshes from 107 to 213 reduced the 50% retention length (L50) for red mullet by2.5 cm but did not affect size selection for the two flat fish species. In some fisheries, regulatoryprovisions regarding the number of meshes in the circumference should therefore becarefully considered both for diamond- and square-mesh codends.