Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates
Discarding can be an unknown source of biases and uncertainties in stock assessments. Discarding patterns and quantities vary so a routine methodology for estimating discards is important to give a better picture of total catches, and potentially mortality, in fisheries. Using data from the Norwegia...
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Oxford University Press
2022
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Online Access: | https://hdl.handle.net/11250/2999554 https://doi.org/10.1093/icesjms/fsac081 |
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ftunivbergen:oai:bora.uib.no:11250/2999554 2023-05-15T16:19:00+02:00 Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates Berg, Hilde Sofie Fantoft Clegg, Thomas L Blom, Geir Kolding, Jeppe Ono, Kotaro Nedreaas, Kjell Harald 2022 application/pdf https://hdl.handle.net/11250/2999554 https://doi.org/10.1093/icesjms/fsac081 eng eng Oxford University Press urn:issn:1054-3139 https://hdl.handle.net/11250/2999554 https://doi.org/10.1093/icesjms/fsac081 cristin:2025894 ICES Journal of Marine Science. 2022, 79 (5), 1548-1560. Navngivelse 4.0 Internasjonal http://creativecommons.org/licenses/by/4.0/deed.no Copyright 2022 the authors fsac081 ICES Journal of Marine Science 1548-1560 79 5 Journal article Peer reviewed 2022 ftunivbergen https://doi.org/10.1093/icesjms/fsac081 2023-03-14T17:39:49Z Discarding can be an unknown source of biases and uncertainties in stock assessments. Discarding patterns and quantities vary so a routine methodology for estimating discards is important to give a better picture of total catches, and potentially mortality, in fisheries. Using data from the Norwegian Reference Fleet between 2012 and 2018, this study presents a revised methodology for estimating discards of cod (Gadus morhua) in the Norwegian coastal gillnet fisheries, which accounts for variations in discarding between vessels and uncertainties in the conversion of numbers to weight discarded. The estimated average discard rate of cod (weight of cod discarded as percentage of total weight caught) is 0.55% (95% confidence interval: 0.45–0.70%), although discard rates in southern areas were an order of magnitude higher than in northern areas. We also present an exploratory analysis of the drivers behind discarding using a random forest regression model. Spatial variations and fishing intensity were identified as the most important drivers of discarding. Results from this study suggest ways in which self-sampled data can be used to estimate discards in Norwegian coastal fisheries, and where the accuracy of future estimates can be improved when a higher resolution data collection programme is established. publishedVersion Article in Journal/Newspaper Gadus morhua University of Bergen: Bergen Open Research Archive (BORA-UiB) ICES Journal of Marine Science 79 5 1548 1560 |
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Open Polar |
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University of Bergen: Bergen Open Research Archive (BORA-UiB) |
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ftunivbergen |
language |
English |
description |
Discarding can be an unknown source of biases and uncertainties in stock assessments. Discarding patterns and quantities vary so a routine methodology for estimating discards is important to give a better picture of total catches, and potentially mortality, in fisheries. Using data from the Norwegian Reference Fleet between 2012 and 2018, this study presents a revised methodology for estimating discards of cod (Gadus morhua) in the Norwegian coastal gillnet fisheries, which accounts for variations in discarding between vessels and uncertainties in the conversion of numbers to weight discarded. The estimated average discard rate of cod (weight of cod discarded as percentage of total weight caught) is 0.55% (95% confidence interval: 0.45–0.70%), although discard rates in southern areas were an order of magnitude higher than in northern areas. We also present an exploratory analysis of the drivers behind discarding using a random forest regression model. Spatial variations and fishing intensity were identified as the most important drivers of discarding. Results from this study suggest ways in which self-sampled data can be used to estimate discards in Norwegian coastal fisheries, and where the accuracy of future estimates can be improved when a higher resolution data collection programme is established. publishedVersion |
format |
Article in Journal/Newspaper |
author |
Berg, Hilde Sofie Fantoft Clegg, Thomas L Blom, Geir Kolding, Jeppe Ono, Kotaro Nedreaas, Kjell Harald |
spellingShingle |
Berg, Hilde Sofie Fantoft Clegg, Thomas L Blom, Geir Kolding, Jeppe Ono, Kotaro Nedreaas, Kjell Harald Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates |
author_facet |
Berg, Hilde Sofie Fantoft Clegg, Thomas L Blom, Geir Kolding, Jeppe Ono, Kotaro Nedreaas, Kjell Harald |
author_sort |
Berg, Hilde Sofie Fantoft |
title |
Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates |
title_short |
Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates |
title_full |
Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates |
title_fullStr |
Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates |
title_full_unstemmed |
Discards of cod (Gadus morhua) in the Norwegian coastal fisheries: improving past and future estimates |
title_sort |
discards of cod (gadus morhua) in the norwegian coastal fisheries: improving past and future estimates |
publisher |
Oxford University Press |
publishDate |
2022 |
url |
https://hdl.handle.net/11250/2999554 https://doi.org/10.1093/icesjms/fsac081 |
genre |
Gadus morhua |
genre_facet |
Gadus morhua |
op_source |
fsac081 ICES Journal of Marine Science 1548-1560 79 5 |
op_relation |
urn:issn:1054-3139 https://hdl.handle.net/11250/2999554 https://doi.org/10.1093/icesjms/fsac081 cristin:2025894 ICES Journal of Marine Science. 2022, 79 (5), 1548-1560. |
op_rights |
Navngivelse 4.0 Internasjonal http://creativecommons.org/licenses/by/4.0/deed.no Copyright 2022 the authors |
op_doi |
https://doi.org/10.1093/icesjms/fsac081 |
container_title |
ICES Journal of Marine Science |
container_volume |
79 |
container_issue |
5 |
container_start_page |
1548 |
op_container_end_page |
1560 |
_version_ |
1766005296152444928 |