Bycatch reduction in the Norwegian Deep-water Shrimp (Pandalus borealis) fishery with a double grid selection system

Published source details Larsen R.B., Herrmann B., Sistiaga M., Brinkhof J. & Grimaldo E. (2018) Bycatch reduction in the Norwegian Deep-water Shrimp (Pandalus borealis) fishery with a double grid selection system. Fisheries Research, 208, 267-273.
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This study is summarised as evidence for the following.

	Action	Category
	Use a different design or configuration of size-sorting escape grid/system in trawl fishing gear (bottom and mid-water) Action Link

Use a different design or configuration of size-sorting escape grid/system in trawl fishing gear (bottom and mid-water)

A controlled study in 2016 of a fished area of seabed in the Barents Sea, Norway (Larsen et al. 2018) found that that using a different type of size-sorting escape grid system (two grids) in shrimp trawls increased the escape of small immature redfish Sebastes spp. and long rough dab Hippoglossoides platessoides, compared to a standard single grid. For small (<10 cm) redfish and long rough dab, the likelihood of being retained in the codend was lower with the dual grid system combined compared to the single grid (data reported as retention probability curves). The proportion of redfish and long rough dab that escaped through the additional second grid was 32% and 16% respectively. The length at which fish had a 50% chance of escape through the second grid was 8 cm for redfish and 10 cm for long rough dab, compared to 14 cm and 18 cm respectively with the single grid (i.e. only the smallest fish escaped from the second grid). Data were collected in February 2016, from eight deployments (1 h) of a trawl net fitted with the double grid system, consisting of a 0.75 × 1.5 m standard escape grid (Nordmøre, 19 mm bar spacing, upward opening), followed by a second 0.6 × 1.2 m ‘release’ grid (9 mm bar spacing, bottom opening). A guiding mesh panel directed catch to the bottom of the Nordmøre grid. Covers attached over the openings of each grid collected fish escaping through them. The codend was fitted with a small mesh liner to prevent fish escaping through the codend meshes (see original paper for gear specifications). The lengths of fish retained in the covers and codend were measured.

(Summarised by: Leo Clarke)