Selectivity experiments to estimate the effect of escape windows in the Skagerak roundfish fishery

Niels Madsen, Karl-Johan Stæhr

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The objectives were to measure roundfish selectivity and to test if square-mesh windows inserted in the codend could improve the selectivity. Sea trials were conducted with a commercial trawler in the Skagerak area. Three codend types were tested: (1) a standard codend with 104 mm meshes; (2) a standard 104 mm codend with two 85 rum square-mesh side windows; (3) a standard 104 mm codend with an 85-mm square-mesh top window. The twin-trawl method was used where one side of the rig had a 35-mm (nominal mesh size) control codend. Hauls of each codend were fitted simultaneously in a fixed- and random-effects model. In total, 24 and 30 hauls of haddock and cod, respectively, were included in the final selectivity analysis. This indicated that insertion of a top window in a standard codend improved the selectivity resulting in a lower selectivity ratio (SR/L50) and a higher L50 for cod and haddock, whereas insertion of side windows gave a lower selectivity ratio for both species, but a higher L50 for cod only. The results suggest that the recent mesh size increase to 120 mm in a standard codend is not sufficient to reduce the probability of discards to a negligible level with the existing minimum landing sizes. (C) 2004 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalFisheries Research
Volume71
Issue number2
Pages (from-to)241-245
ISSN0165-7836
DOIs
Publication statusPublished - 2005

Cite this

@article{3db35a70d3a5449881146db66df2e4db,
title = "Selectivity experiments to estimate the effect of escape windows in the Skagerak roundfish fishery",
abstract = "The objectives were to measure roundfish selectivity and to test if square-mesh windows inserted in the codend could improve the selectivity. Sea trials were conducted with a commercial trawler in the Skagerak area. Three codend types were tested: (1) a standard codend with 104 mm meshes; (2) a standard 104 mm codend with two 85 rum square-mesh side windows; (3) a standard 104 mm codend with an 85-mm square-mesh top window. The twin-trawl method was used where one side of the rig had a 35-mm (nominal mesh size) control codend. Hauls of each codend were fitted simultaneously in a fixed- and random-effects model. In total, 24 and 30 hauls of haddock and cod, respectively, were included in the final selectivity analysis. This indicated that insertion of a top window in a standard codend improved the selectivity resulting in a lower selectivity ratio (SR/L50) and a higher L50 for cod and haddock, whereas insertion of side windows gave a lower selectivity ratio for both species, but a higher L50 for cod only. The results suggest that the recent mesh size increase to 120 mm in a standard codend is not sufficient to reduce the probability of discards to a negligible level with the existing minimum landing sizes. (C) 2004 Elsevier B.V. All rights reserved.",
keywords = "Erhvervsfiskeri",
author = "Niels Madsen and Karl-Johan St{\ae}hr",
year = "2005",
doi = "10.1016/j.fishres.2004.08.019",
language = "English",
volume = "71",
pages = "241--245",
journal = "Fisheries Research",
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}

Selectivity experiments to estimate the effect of escape windows in the Skagerak roundfish fishery. / Madsen, Niels; Stæhr, Karl-Johan.

In: Fisheries Research, Vol. 71, No. 2, 2005, p. 241-245.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Selectivity experiments to estimate the effect of escape windows in the Skagerak roundfish fishery

AU - Madsen, Niels

AU - Stæhr, Karl-Johan

PY - 2005

Y1 - 2005

N2 - The objectives were to measure roundfish selectivity and to test if square-mesh windows inserted in the codend could improve the selectivity. Sea trials were conducted with a commercial trawler in the Skagerak area. Three codend types were tested: (1) a standard codend with 104 mm meshes; (2) a standard 104 mm codend with two 85 rum square-mesh side windows; (3) a standard 104 mm codend with an 85-mm square-mesh top window. The twin-trawl method was used where one side of the rig had a 35-mm (nominal mesh size) control codend. Hauls of each codend were fitted simultaneously in a fixed- and random-effects model. In total, 24 and 30 hauls of haddock and cod, respectively, were included in the final selectivity analysis. This indicated that insertion of a top window in a standard codend improved the selectivity resulting in a lower selectivity ratio (SR/L50) and a higher L50 for cod and haddock, whereas insertion of side windows gave a lower selectivity ratio for both species, but a higher L50 for cod only. The results suggest that the recent mesh size increase to 120 mm in a standard codend is not sufficient to reduce the probability of discards to a negligible level with the existing minimum landing sizes. (C) 2004 Elsevier B.V. All rights reserved.

AB - The objectives were to measure roundfish selectivity and to test if square-mesh windows inserted in the codend could improve the selectivity. Sea trials were conducted with a commercial trawler in the Skagerak area. Three codend types were tested: (1) a standard codend with 104 mm meshes; (2) a standard 104 mm codend with two 85 rum square-mesh side windows; (3) a standard 104 mm codend with an 85-mm square-mesh top window. The twin-trawl method was used where one side of the rig had a 35-mm (nominal mesh size) control codend. Hauls of each codend were fitted simultaneously in a fixed- and random-effects model. In total, 24 and 30 hauls of haddock and cod, respectively, were included in the final selectivity analysis. This indicated that insertion of a top window in a standard codend improved the selectivity resulting in a lower selectivity ratio (SR/L50) and a higher L50 for cod and haddock, whereas insertion of side windows gave a lower selectivity ratio for both species, but a higher L50 for cod only. The results suggest that the recent mesh size increase to 120 mm in a standard codend is not sufficient to reduce the probability of discards to a negligible level with the existing minimum landing sizes. (C) 2004 Elsevier B.V. All rights reserved.

KW - Erhvervsfiskeri

U2 - 10.1016/j.fishres.2004.08.019

DO - 10.1016/j.fishres.2004.08.019

M3 - Journal article

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JO - Fisheries Research

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SN - 0165-7836

IS - 2

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