Size selection of cod by rigid grids—is anything gained compared to diamond mesh codends only?

Published source details Jørgensen T., Ingólfsson Ó.A., Graham N. & Isaksen B. (2006) Size selection of cod by rigid grids—is anything gained compared to diamond mesh codends only?. Fisheries Research, 79, 337-348.
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This study is summarised as evidence for the following.

	Action	Category
	Fit a size-sorting escape grid (rigid or flexible) to a fish trawl net Action Link

Fit a size-sorting escape grid (rigid or flexible) to a fish trawl net

A replicated, paired, controlled study in 2002–2003 of bottom fishing grounds in the Barents Sea, Norway (Jørgensen et al. 2006) found that fish trawl nets fitted with a rigid size-sorting escape grid (Sort-V) reduced the unwanted catch of smaller Atlantic cod Gadus morhua, compared to conventional trawl nets without a grid. In two of two trials, the average lengths at which 50% of cod escaped capture and half were retained (selection length) was larger in trawl nets with grids (55 and 54 cm) than without (44 and 50 cm). In 2002–2003, data were collected from experimental trawl deployments off the coast of Finnmark targeting cod. Two sampling methods were used. In 2002, a conventional 135 mm diamond mesh trawl was tested with (17 tows) or without (14 tows) a rigid 55 mm sorting grid. Small-mesh covers installed over the escape outlet of the grid and the codends collected the escaped and retained catch respectively. In 2003, seven paired tows were done with a twin trawler where one side was fished with a conventional 135 mm mesh trawl net with a sorting grid and the other fished with a fine-mesh inner liner. A further nine paired tows were done in the same way with a conventional net without a grid (see paper for specifications).

(Summarised by: Leo Clarke)