Initial tests of a bycatch reduction device designed to improve trawl selectivity in the west coast limited entry groundfish bottom trawl directed flatfish fishery


Lomeli, M.J.M. and Wakefield, W.W.



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NMFS Northwest Fisheries Science Center Report

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A flexible sorting grid was tested in the US west coast groundfish trawl fishery for its ability to reduce the bycatch of rockfish, sablefish and Pacific halibut without reducing catches of targeted flatfish. The grid works by allowing fish smaller than it to enter the codend, while fish larger than the grid openings are able to escape. The flexible sorting grid used four-seam tube of netting 80 meshes deep and 100 meshes in circumference. It was inserted between the intermediate section of the bottom trawl and codend. Two vertical panels were used to direct fish towards an upward ramp. A recapture net was used to quantify retention and escapements. Retention of flatfish species ranged from 74.8-93.3%. Retention was highest for Petrale sole (93.3%), Dover sole (89.4%) and English sole (87.9%). Rockfish that were 36 cm or larger had the largest escapement rate of 94.6%. For lingcod and sablefish, 92% of fish 38 cm or larger escaped. For targeted flatfish, 85.1% that were encountered were retained. For bycatch species, 72.1% of rockfish, 96.5% of roundfishes and 93.7% of Pacific halibut that were encountered were able to escape.