A flexible sorting grid to reduce Pacific halibut (Hippoglossus stenolepis) bycatch in the US west coast groundfish bottom trawl fishery

Published source details Lomeli M.J.M. & Wakefield W.W. (2013) A flexible sorting grid to reduce Pacific halibut (Hippoglossus stenolepis) bycatch in the US west coast groundfish bottom trawl fishery. Fisheries Research, 143, 102-108.
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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 study in 2011 of a deep seabed area in the North Pacific Ocean off Washington, USA (Lomeli & Wakefield 2013) reported that fitting a flexible size-sorting escape grid system allowed the escape of prohibited Pacific halibut Hippoglossus stenolepis in a groundfish bottom trawl fishery and, to a lesser extent, unmarketable sizes of other fish species. Data (except halibut length) were not tested for statistical significance. Overall, 62% of the halibut escaped capture through the grid relative to the weight retained in the codend (grid: 308 kg, codend: 192 kg) and they were larger in size (grid: 74.5 cm, codend: 70.0 cm). For the target fish species/groups (see paper for list), between 0–23% of other flatfish, 6–11% of roundfish and 0–77% of skates of unmarketable sizes were sorted out by the grid. In addition, of marketable sizes, an average of 77–87% of other flatfishes, 83–89% of roundfishes and 6–13% of skates of were retained. Trials were carried out using a low-rise flatfish trawl net with a cutback headrope, fitted with a grid system. Data were collected from 30 trawl deployments of 28–30 min, in depths of 113–173 m and at speeds of 2.7–3.2 knots. The grid system was inserted in front of the codend and consisted of two flexible vertical grids (19 ×19 cm openings) to direct fish toward a downward-angled escape panel (see paper for full gear specifications). A cover installed over the escape openings collected escaping fish. Cover and codend catches were sorted and sampled.

(Summarised by: Chris Barrett/Natasha Taylor)