Variations in the target strength of Atlantic cod during vertical migration

<qd> Rose, G. A. 2009. Variations in the target strength of Atlantic cod during vertical migration. – ICES Journal of Marine Science, 66: 1205–1211. </qd>Experiments conducted at sea in June 1999 and January 2000 indicated that the mean target strength ( TS ) of Atlantic cod ( Gadus morh...

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Published in:ICES Journal of Marine Science
Main Author: Rose, George A.
Format: Text
Language:English
Published: Oxford University Press 2009
Subjects:
Online Access:http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1205
https://doi.org/10.1093/icesjms/fsp085
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spelling fthighwire:oai:open-archive.highwire.org:icesjms:66/6/1205 2023-05-15T15:27:10+02:00 Variations in the target strength of Atlantic cod during vertical migration Rose, George A. 2009-07-01 00:00:00.0 text/html http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1205 https://doi.org/10.1093/icesjms/fsp085 en eng Oxford University Press http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1205 http://dx.doi.org/10.1093/icesjms/fsp085 Copyright (C) 2009, International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer Articles TEXT 2009 fthighwire https://doi.org/10.1093/icesjms/fsp085 2009-07-03T20:19:12Z <qd> Rose, G. A. 2009. Variations in the target strength of Atlantic cod during vertical migration. – ICES Journal of Marine Science, 66: 1205–1211. </qd>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 ( TS individual ) and mean TS inferred from a comparison of area-backscattering coefficients ( s a ) and count-based densities ( TS indirect ) 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 TS individual and TS indirect . Text atlantic cod Gadus morhua HighWire Press (Stanford University) ICES Journal of Marine Science 66 6 1205 1211
institution Open Polar
collection HighWire Press (Stanford University)
op_collection_id fthighwire
language English
topic Articles
spellingShingle Articles
Rose, George A.
Variations in the target strength of Atlantic cod during vertical migration
topic_facet Articles
description <qd> Rose, G. A. 2009. Variations in the target strength of Atlantic cod during vertical migration. – ICES Journal of Marine Science, 66: 1205–1211. </qd>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 ( TS individual ) and mean TS inferred from a comparison of area-backscattering coefficients ( s a ) and count-based densities ( TS indirect ) 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 TS individual and TS indirect .
format Text
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
publishDate 2009
url http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1205
https://doi.org/10.1093/icesjms/fsp085
genre atlantic cod
Gadus morhua
genre_facet atlantic cod
Gadus morhua
op_relation http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1205
http://dx.doi.org/10.1093/icesjms/fsp085
op_rights Copyright (C) 2009, International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
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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