The effect of forced mesh opening in the upper panel of a Nephrops trawl on size selection of Nephrops, haddock and whiting

Published source details Ingólfsson Ó.A. (2011) The effect of forced mesh opening in the upper panel of a Nephrops trawl on size selection of Nephrops, haddock and whiting. Fisheries Research, 108, 218-222
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This study is summarised as evidence for the following.

	Action	Category
	Fit mesh escape panels/windows to a trawl net Action Link

Fit mesh escape panels/windows to a trawl net

A replicated, paired, controlled study in 2009 of bottom fishing grounds in the northeast Atlantic Ocean off Iceland (Ingólfsson 2011) found that one of two designs of a diamond mesh escape panel fitted to prawn trawl nets, reduced the catches of unwanted and undersized whiting Merlangius merlangus and haddock Melanogrammus aeglefinus, compared to standard trawl nets with two square mesh escape panels. Overall, diamond mesh escape panels reduced the total catches of whiting and haddock by 43–48% and 34–57% respectively compared to the square mesh panel trawls. However, only the shorter design of large mesh panel reduced the catches of smaller individuals, and there were no size related differences for haddock and cod in the longer panel design (data reported as statistical models). In addition, target Norway lobster Nephrops norvegicus catches were reduced by 16–42% and fewer smaller (<50 mm) Nephrops were caught in the shorter panel trawl. In June 2009, data were collected from 22 deployments of two test nets and a standard Nephrops trawl nets towed in pairs on a commercial twin-rig vessel. In modified nets, the 135 mm diamond mesh top panel was narrower and longer than the bottom panel resulting in forced opening of the meshes. One design had a 23.2 m long upper panel (five tows) and the other a 16.1 m long upper panel (17 tows). Standard trawl nets were identical except for two mandatory 200 mm square mesh upper panels in place of the test diamond mesh panels. Full trawl details are given in the original study.

(Summarised by: Leo Clarke)