Abstract
It is well established that increasing mesh number in the circumference of a diamond-mesh trawl codend can reduce size selection for round fish, whereas selection for flat fish species is unaffected. This effect has also been documented in Mediterranean trawl fisheries. In contrast, no information is available with regard to the effect of increasing mesh number in the circumference of square-mesh codends on the size selection of round fish and flat fish species. A field study was devised to bridge this gap and formulate proposals aimed at improving trawl fishery management. Size selection data were collected for a round fish species, red mullet (Mullus barbatus), and two flat fish species, Mediterranean scaldfish (Arnoglossus laterna) and solenette (Buglossidium luteum). Fishing trials were conducted in the Adriatic Sea (Central Mediterranean) using three square-mesh codends that differed only in mesh number around the circumference. Results demonstrated that increasing the number of meshes from 107 to 213 reduced the 50% retention length (L50) for red mullet by 2.5 cm but did not affect size selection for the two flat fish species. In some fisheries, regulatory provisions regarding the number of meshes in the circumference should therefore be carefully considered both for diamond- and square-mesh codends.
Highlights
Codend size selection depends both on fish morphology and on mesh geometry [1]
The present study investigates the effect of number of meshes around the square-mesh codend circumference on size selectivity for Mediterranean round and flat fish species
The codend with 213 meshes (C213) and the cover caught 111 red mullet specimens; the total length (TL) of retained individuals was 8.5–15.5 cm in the codend and 7.5–13.5 cm in the cover
Summary
Codend size selection depends both on fish morphology (flat/round cross-section) and on mesh geometry [1]. Mesh geometry depends on mesh size as well as shape [2]. These effects have clearly been documented in the diamond-mesh codend, whose construction simplicity makes it the most widely used codend type in several European trawl fisheries [3,4,5,6]. The shape of an ideal diamond mesh depends only on its size and opening angle. When the diamondmesh codend is towed through the sea, the drag forces acting on the catch in the aft portion of the codend tend to stretch the meshes in most codend areas, causing a reduction in the opening.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
