Broadening the horizon of size selectivity in trawl gears

Published source details Stepputtis D., Santos J., Herrmann B. & Mieske B. (2016) Broadening the horizon of size selectivity in trawl gears. Fisheries Research, 184, 18-25.
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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 2014 of a bottom fishing ground in the western Baltic Sea, northern Europe (Stepputtis et al. 2016) found that fitting a rigid size-sorting escape grid to a fish trawl net resulted in reduced catches of cod Gadus morhua and an increase in the escape of cod of unwanted sizes, in addition to the sizes sorted out by the mesh of the codend. Total numbers of cod that escaped from the net were 3,881 fish (1,608 kg) through the grid and 3,918 fish (1,150 kg) through the meshes of the codend, and the number of cod retained in the codend was 4,715 fish (2,617 kg). In addition, the average length at which half of the cod were likely to escape from each part of the net was 47.9 cm for the grid and 29.7 cm for the codend itself. Data were collected from eight bottom trawl deployments by a research vessel in March 2014 in the Baltic Sea cod fishery. A steel grid, with 50 mm bar spacing, a guiding panel and a top escape opening, was fitted to a standard diamond mesh trawl. A rectangular piece of netting was mounted over the opening to make it less visible to fish and increase fish contact with the grid. Deployments were 90–120 min, towed at three knots. Covers fitted over the grid opening and over the codend collected all cod escaping through them. Cod collected in the two covers and retained in the codend were counted and their lengths measured.

(Summarised by: Rosslyn McIntyre)