Variations in the target strength of Atlantic cod during vertical migration
Abstract Rose, G. A. 2009. Variations in the target strength of Atlantic cod during vertical migration. – ICES Journal of Marine Science, 66: 1205–1211. Experiments conducted at sea in June 1999 and January 2000 indicated that the mean target strength (TS) of Atlantic cod (Gadus morhua) varies not j...
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Online Access: | http://dx.doi.org/10.1093/icesjms/fsp085 http://academic.oup.com/icesjms/article-pdf/66/6/1205/29133938/fsp085.pdf |
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croxfordunivpr:10.1093/icesjms/fsp085 2023-09-05T13:17:59+02:00 Variations in the target strength of Atlantic cod during vertical migration Rose, George A. 2009 http://dx.doi.org/10.1093/icesjms/fsp085 http://academic.oup.com/icesjms/article-pdf/66/6/1205/29133938/fsp085.pdf en eng Oxford University Press (OUP) ICES Journal of Marine Science volume 66, issue 6, page 1205-1211 ISSN 1095-9289 1054-3139 Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography journal-article 2009 croxfordunivpr https://doi.org/10.1093/icesjms/fsp085 2023-08-18T09:57:49Z Abstract Rose, G. A. 2009. Variations in the target strength of Atlantic cod during vertical migration. – ICES Journal of Marine Science, 66: 1205–1211. Experiments conducted at sea in June 1999 and January 2000 indicated that the mean target strength (TS) of Atlantic cod (Gadus morhua) varies not just with length, but also with pressure (depth) and fish orientation, particularly during vertical migration. In June, when fish were migrating and spawning, vertical migration was pronounced, extending up to 150 m off the seabed, and the associated TS declined by as much as 5 dB. In January, when the fish were located nearer the seabed, mean TS was more stable and matched a conventional model of TS vs. length [L, cm; i.e. TS = 20 log(L) − 66] based on measurements of ex situ fish orientated horizontally and positioned at close range. This paper demonstrates that mean TS is inversely related (p < 0.05) to the range off the seabed (r, m), which includes 90% of fish. Based on this finding, a new multivariate TS model is proposed: TS = 20 log(L) − 65 − 0.05 r. In this model, r is a proxy for swimbladder volume and fish orientation. A survey in May 2007 found that cod (mean L = 63 cm) dispersed in such a way that single targets could be resolved up to 100 m from the seabed. Measurements of TS of in situ individual fish (TSindividual) and mean TS inferred from a comparison of area-backscattering coefficients (sa) and count-based densities (TSindirect) were positively correlated with a slope not different from unity. Means of these TS estimates were −32.4 and −32.2 dB, respectively, or ∼2.3 dB less than that predicted by the conventional model. In contrast, the new multivariate model predicts TS = −32.5 dB, which is nearly identical with the means of TSindividual and TSindirect. Article in Journal/Newspaper atlantic cod Gadus morhua Oxford University Press (via Crossref) ICES Journal of Marine Science 66 6 1205 1211 |
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Open Polar |
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Oxford University Press (via Crossref) |
op_collection_id |
croxfordunivpr |
language |
English |
topic |
Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography |
spellingShingle |
Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography Rose, George A. Variations in the target strength of Atlantic cod during vertical migration |
topic_facet |
Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography |
description |
Abstract Rose, G. A. 2009. Variations in the target strength of Atlantic cod during vertical migration. – ICES Journal of Marine Science, 66: 1205–1211. Experiments conducted at sea in June 1999 and January 2000 indicated that the mean target strength (TS) of Atlantic cod (Gadus morhua) varies not just with length, but also with pressure (depth) and fish orientation, particularly during vertical migration. In June, when fish were migrating and spawning, vertical migration was pronounced, extending up to 150 m off the seabed, and the associated TS declined by as much as 5 dB. In January, when the fish were located nearer the seabed, mean TS was more stable and matched a conventional model of TS vs. length [L, cm; i.e. TS = 20 log(L) − 66] based on measurements of ex situ fish orientated horizontally and positioned at close range. This paper demonstrates that mean TS is inversely related (p < 0.05) to the range off the seabed (r, m), which includes 90% of fish. Based on this finding, a new multivariate TS model is proposed: TS = 20 log(L) − 65 − 0.05 r. In this model, r is a proxy for swimbladder volume and fish orientation. A survey in May 2007 found that cod (mean L = 63 cm) dispersed in such a way that single targets could be resolved up to 100 m from the seabed. Measurements of TS of in situ individual fish (TSindividual) and mean TS inferred from a comparison of area-backscattering coefficients (sa) and count-based densities (TSindirect) were positively correlated with a slope not different from unity. Means of these TS estimates were −32.4 and −32.2 dB, respectively, or ∼2.3 dB less than that predicted by the conventional model. In contrast, the new multivariate model predicts TS = −32.5 dB, which is nearly identical with the means of TSindividual and TSindirect. |
format |
Article in Journal/Newspaper |
author |
Rose, George A. |
author_facet |
Rose, George A. |
author_sort |
Rose, George A. |
title |
Variations in the target strength of Atlantic cod during vertical migration |
title_short |
Variations in the target strength of Atlantic cod during vertical migration |
title_full |
Variations in the target strength of Atlantic cod during vertical migration |
title_fullStr |
Variations in the target strength of Atlantic cod during vertical migration |
title_full_unstemmed |
Variations in the target strength of Atlantic cod during vertical migration |
title_sort |
variations in the target strength of atlantic cod during vertical migration |
publisher |
Oxford University Press (OUP) |
publishDate |
2009 |
url |
http://dx.doi.org/10.1093/icesjms/fsp085 http://academic.oup.com/icesjms/article-pdf/66/6/1205/29133938/fsp085.pdf |
genre |
atlantic cod Gadus morhua |
genre_facet |
atlantic cod Gadus morhua |
op_source |
ICES Journal of Marine Science volume 66, issue 6, page 1205-1211 ISSN 1095-9289 1054-3139 |
op_doi |
https://doi.org/10.1093/icesjms/fsp085 |
container_title |
ICES Journal of Marine Science |
container_volume |
66 |
container_issue |
6 |
container_start_page |
1205 |
op_container_end_page |
1211 |
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1776199054184677376 |