Diurnal variation in bottom trawl survey catches: does it pay to adjust?
The diurnal bias of bottom trawl survey catches is studied with the purpose of adjusting for it and thereby improving the accuracy of abundance estimates. The correction term is estimated with uncertainty and thus increases the variance of the resulting abundance estimate. To investigate this adequa...
Published in: | Canadian Journal of Fisheries and Aquatic Sciences |
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Language: | English |
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2002
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Online Access: | http://hdl.handle.net/11250/108806 https://doi.org/10.1139/F01-193 |
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ftimr:oai:imr.brage.unit.no:11250/108806 2024-09-15T17:57:56+00:00 Diurnal variation in bottom trawl survey catches: does it pay to adjust? Hjellvik, Vidar Godø, Olav Rune Tjøstheim, Dag 2002 4892314 bytes application/pdf http://hdl.handle.net/11250/108806 https://doi.org/10.1139/F01-193 eng eng urn:issn:0706-652X http://hdl.handle.net/11250/108806 http://dx.doi.org/10.1139/F01-193 33-48 59 Canadian Journal of Fisheries and Aquatic Sciences 1 Barents Sea bottom trawl Barentshavet bunntrål Journal article Peer reviewed 2002 ftimr https://doi.org/10.1139/F01-193 2024-07-31T03:37:25Z The diurnal bias of bottom trawl survey catches is studied with the purpose of adjusting for it and thereby improving the accuracy of abundance estimates. The correction term is estimated with uncertainty and thus increases the variance of the resulting abundance estimate. To investigate this adequately, we use a stochastic model describing diurnal fluctuations and examine the annual variation of the diurnal amplitude as a function of species and length. The diurnal amplitude is fairly stable for large fish, and for these, the bias-corrected estimate leads to a moderate increase in variance. For small fish, the diurnal amplitude is unstable, however, and the correction of diurnal bias occurs at the expense of a large increase in variance. This unstable amplitude also leads to a large year-to-year variation in catchability for small fish. For haddock (Melanogrammus aeglefinus), the diurnal amplitude depends heavily on fish length, indicating a strong decrease in catchability with decreasing fish length. Article in Journal/Newspaper Barents Sea Barentshav* Institute for Marine Research: Brage IMR Canadian Journal of Fisheries and Aquatic Sciences 59 1 33 48 |
institution |
Open Polar |
collection |
Institute for Marine Research: Brage IMR |
op_collection_id |
ftimr |
language |
English |
topic |
Barents Sea bottom trawl Barentshavet bunntrål |
spellingShingle |
Barents Sea bottom trawl Barentshavet bunntrål Hjellvik, Vidar Godø, Olav Rune Tjøstheim, Dag Diurnal variation in bottom trawl survey catches: does it pay to adjust? |
topic_facet |
Barents Sea bottom trawl Barentshavet bunntrål |
description |
The diurnal bias of bottom trawl survey catches is studied with the purpose of adjusting for it and thereby improving the accuracy of abundance estimates. The correction term is estimated with uncertainty and thus increases the variance of the resulting abundance estimate. To investigate this adequately, we use a stochastic model describing diurnal fluctuations and examine the annual variation of the diurnal amplitude as a function of species and length. The diurnal amplitude is fairly stable for large fish, and for these, the bias-corrected estimate leads to a moderate increase in variance. For small fish, the diurnal amplitude is unstable, however, and the correction of diurnal bias occurs at the expense of a large increase in variance. This unstable amplitude also leads to a large year-to-year variation in catchability for small fish. For haddock (Melanogrammus aeglefinus), the diurnal amplitude depends heavily on fish length, indicating a strong decrease in catchability with decreasing fish length. |
format |
Article in Journal/Newspaper |
author |
Hjellvik, Vidar Godø, Olav Rune Tjøstheim, Dag |
author_facet |
Hjellvik, Vidar Godø, Olav Rune Tjøstheim, Dag |
author_sort |
Hjellvik, Vidar |
title |
Diurnal variation in bottom trawl survey catches: does it pay to adjust? |
title_short |
Diurnal variation in bottom trawl survey catches: does it pay to adjust? |
title_full |
Diurnal variation in bottom trawl survey catches: does it pay to adjust? |
title_fullStr |
Diurnal variation in bottom trawl survey catches: does it pay to adjust? |
title_full_unstemmed |
Diurnal variation in bottom trawl survey catches: does it pay to adjust? |
title_sort |
diurnal variation in bottom trawl survey catches: does it pay to adjust? |
publishDate |
2002 |
url |
http://hdl.handle.net/11250/108806 https://doi.org/10.1139/F01-193 |
genre |
Barents Sea Barentshav* |
genre_facet |
Barents Sea Barentshav* |
op_source |
33-48 59 Canadian Journal of Fisheries and Aquatic Sciences 1 |
op_relation |
urn:issn:0706-652X http://hdl.handle.net/11250/108806 http://dx.doi.org/10.1139/F01-193 |
op_doi |
https://doi.org/10.1139/F01-193 |
container_title |
Canadian Journal of Fisheries and Aquatic Sciences |
container_volume |
59 |
container_issue |
1 |
container_start_page |
33 |
op_container_end_page |
48 |
_version_ |
1810434148244914176 |