Size selection by diamond- and square-mesh codends in multi-species Mediterranean demersal trawl fisheries

Published source details Sala A., Lucchetti A., Piccinetti C. & Ferretti M. (2008) Size selection by diamond- and square-mesh codends in multi-species Mediterranean demersal trawl fisheries. Fisheries Research, 93, 8-21.
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This study is summarised as evidence for the following.

	Action	Category
	Use a square mesh instead of a diamond mesh codend in a trawl net Action Link

Use a square mesh instead of a diamond mesh codend in a trawl net

A replicated, controlled study in 2004 in one shallow inshore and one deeper offshore seabed area in the Adriatic Sea, Italy (Sala et al. 2008) found that for five roundfish species, but not one flatfish species, using a square mesh codend improved the size selectivity of a bottom trawl net compared with a diamond mesh codend. Overall, the length at which 50% of fish are predicted to escape was greater in the square mesh codend for European hake Merluccius merluccius (square: 14 cm, diamond: 8 cm), red mullet Mullus barbatus (square: 11 cm, diamond: 8 cm), common pandora Pagellus erythrinus (square: 10 cm, diamond: 8 cm), Mediterranean horse mackerel Trachurus mediterraneus (square: 13 cm, diamond: 10 cm) and poor cod Trisopterus minutus capelanus (square: 11 cm, diamond: 8 cm), but was lower for one flatfish, scaldfish Arnoglossus laterna (square: 8 cm, diamond: 8 cm). Fishing surveys were done by research vessel on two fishing grounds in the Central Adriatic: in August–September 2004 (15–21 m depth, 5nm off Ancona), and in September–October 2004 (70 m depth, Western Pomo pit). Two trawl codends with the same mesh size (38 mm) but different mesh configuration (square and diamond mesh) were fished daily and alternately on the same trawl for a total of 48 deployments (21 shallow, 27 deeper). A small mesh cover (20 mm) attached over each codend collected the escaping fish catch. Catches in both the codends and covers were sampled by species and fish total length.

(Summarised by: Chris Barrett)