Diamond- vs. square-mesh codend selectivity in southeastern Australian estuarine squid trawls

Published source details Broadhurst M.K., Millar R.B. & Brand C.P. (2010) Diamond- vs. square-mesh codend selectivity in southeastern Australian estuarine squid trawls. Fisheries Research, 102, 276-285.
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This study is summarised as evidence for the following.

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	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 2008–2009 of an area of seabed in an estuary off the Tasman Sea, Australia (Broadhurst et al. 2010) found that using a square mesh codend in a squid trawl net did not reduce the overall amount of discarded catch (fish and invertebrates), or improve the size selectivity for yellowtail scad Trachurus novaezelandiae and striped seapike Sphyraena obtusata, compared to a diamond mesh codend. Average numbers of total discarded catch (fish and invertebrate species combined – see paper for species caught) were similar for each of two sizes of square mesh codend (29 and 32 mm) compared to a 41 mm diamond mesh codend (29 mm square: 715 ind; 32 mm square: 250 ind; diamond: 300–500 ind). In addition, no statistical differences between square and diamond mesh codends were found in the length at which 50% of fish are predicted to escape for two fish species caught in the covers in sufficient quantities: yellowtail scad (square: 13 cm; diamond: 11–12 cm); and striped seapike (square: 20 cm; diamond: 15 cm). Catches from three different codends (29 and 32 mm square mesh, and 41 mm diamond mesh) were compared on a single-rigged trawler on a commercial squid Loliginidae spp. trawl ground in the Hawkesbury River estuary, in December 2008 and May 2009. All codends also had a 42 mm square mesh escape panel fitted in front. A total of between 10 and 12 deployments (75 min) of each codend were done. A small mesh (18 mm) hooped cover attached over each codend sampled the escaping catch.

(Summarised by: Khatija Alliji)