Diurnal variation in acoustic densities: why do we see less in the dark?
Diurnal fluctuations in total integrated echo abundance and in vertical density profiles were examined using data from the Norwegian combined acoustic and bottom-trawl survey for demersal fish during winter in the Barents Sea. The total echo abundance was about 40%50% higher at day than at night. A...
Published in: | Canadian Journal of Fisheries and Aquatic Sciences |
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2004
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Online Access: | http://dx.doi.org/10.1139/f04-161 http://www.nrcresearchpress.com/doi/pdf/10.1139/f04-161 |
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crcansciencepubl:10.1139/f04-161 2023-12-17T10:27:51+01:00 Diurnal variation in acoustic densities: why do we see less in the dark? Hjellvik, Vidar Godø, Olav Rune Tjøstheim, Dag 2004 http://dx.doi.org/10.1139/f04-161 http://www.nrcresearchpress.com/doi/pdf/10.1139/f04-161 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Fisheries and Aquatic Sciences volume 61, issue 11, page 2237-2254 ISSN 0706-652X 1205-7533 Aquatic Science Ecology, Evolution, Behavior and Systematics journal-article 2004 crcansciencepubl https://doi.org/10.1139/f04-161 2023-11-19T13:38:52Z Diurnal fluctuations in total integrated echo abundance and in vertical density profiles were examined using data from the Norwegian combined acoustic and bottom-trawl survey for demersal fish during winter in the Barents Sea. The total echo abundance was about 40%50% higher at day than at night. An unknown amount of fish was lost close to the seabed in the acoustic dead zone, but the systematic changes in the near-bottom vertical density profiles did not indicate that migration in and out of the dead zone was the major reason for the large diurnal differences in echo abundance. A more plausible explanation could be that diurnal changes in fish behaviour affect the mean acoustic target strength. Based on the present study, we recommend that the time series of acoustic surveys should be re analysed, taking the diurnal bias into account. Any comparison of the fish densities indicated by trawl and acoustic surveys will suffer if this bias is not corrected. We believe that model development utilizing this type of information is crucial for future ecosystem-based monitoring. Article in Journal/Newspaper Barents Sea Canadian Science Publishing (via Crossref) Barents Sea Canadian Journal of Fisheries and Aquatic Sciences 61 11 2237 2254 |
institution |
Open Polar |
collection |
Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
Aquatic Science Ecology, Evolution, Behavior and Systematics |
spellingShingle |
Aquatic Science Ecology, Evolution, Behavior and Systematics Hjellvik, Vidar Godø, Olav Rune Tjøstheim, Dag Diurnal variation in acoustic densities: why do we see less in the dark? |
topic_facet |
Aquatic Science Ecology, Evolution, Behavior and Systematics |
description |
Diurnal fluctuations in total integrated echo abundance and in vertical density profiles were examined using data from the Norwegian combined acoustic and bottom-trawl survey for demersal fish during winter in the Barents Sea. The total echo abundance was about 40%50% higher at day than at night. An unknown amount of fish was lost close to the seabed in the acoustic dead zone, but the systematic changes in the near-bottom vertical density profiles did not indicate that migration in and out of the dead zone was the major reason for the large diurnal differences in echo abundance. A more plausible explanation could be that diurnal changes in fish behaviour affect the mean acoustic target strength. Based on the present study, we recommend that the time series of acoustic surveys should be re analysed, taking the diurnal bias into account. Any comparison of the fish densities indicated by trawl and acoustic surveys will suffer if this bias is not corrected. We believe that model development utilizing this type of information is crucial for future ecosystem-based monitoring. |
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 acoustic densities: why do we see less in the dark? |
title_short |
Diurnal variation in acoustic densities: why do we see less in the dark? |
title_full |
Diurnal variation in acoustic densities: why do we see less in the dark? |
title_fullStr |
Diurnal variation in acoustic densities: why do we see less in the dark? |
title_full_unstemmed |
Diurnal variation in acoustic densities: why do we see less in the dark? |
title_sort |
diurnal variation in acoustic densities: why do we see less in the dark? |
publisher |
Canadian Science Publishing |
publishDate |
2004 |
url |
http://dx.doi.org/10.1139/f04-161 http://www.nrcresearchpress.com/doi/pdf/10.1139/f04-161 |
geographic |
Barents Sea |
geographic_facet |
Barents Sea |
genre |
Barents Sea |
genre_facet |
Barents Sea |
op_source |
Canadian Journal of Fisheries and Aquatic Sciences volume 61, issue 11, page 2237-2254 ISSN 0706-652X 1205-7533 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/f04-161 |
container_title |
Canadian Journal of Fisheries and Aquatic Sciences |
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61 |
container_issue |
11 |
container_start_page |
2237 |
op_container_end_page |
2254 |
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1785579772717301760 |