The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish
<qd> Mello, L. G. S., and Rose, G. A. 2009. The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish. – ICES Journal of Marine Science, 66: 1364–1369. </qd>The height of the acoustic dead zone, the region near the seabed wh...
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fthighwire:oai:open-archive.highwire.org:icesjms:66/6/1364 2023-05-15T15:27:45+02:00 The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish Mello, L. G. S. Rose, G. A. 2009-07-01 00:00:00.0 text/html http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1364 https://doi.org/10.1093/icesjms/fsp099 en eng Oxford University Press http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1364 http://dx.doi.org/10.1093/icesjms/fsp099 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/fsp099 2009-07-03T20:19:12Z <qd> Mello, L. G. S., and Rose, G. A. 2009. The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish. – ICES Journal of Marine Science, 66: 1364–1369. </qd>The height of the acoustic dead zone, the region near the seabed where fish cannot be resolved acoustically, was calculated both theoretically (DZ t ) and empirically (DZ e ). The DZ e was based on measurements of depth and trawl geometry from sensors (SCANMAR) mounted on a bottom trawl deployed during a survey off Newfoundland and Labrador in winter 2007. Acoustic data were acquired while trawling, using a 38-kHz echosounder (Simrad EK500) with a hull-mounted transducer. The DZ e was calculated as the difference between the trawl-footrope depth and the corresponding acoustically sensed, seabed depth. EK500 and SCANMAR estimates of seabed depth were significantly different. The fish caught were mostly Atlantic cod ( Gadus morhua ). The estimates of DZ e ranged between 2.0 and 3.5 m and were greater than DZ t by 0.1–0.9 m in more than half the cases. Three values of acoustically derived cod densities were estimated for each tow, without dead-zone correction and with corrections for DZ t and DZ e . When compared with DZ t corrections, DZ e resulted in negative (6–12%) and positive (9–35%) corrections to cod density. A general linear model revealed that the seabed depth gradient, standard deviation of estimated fish density in the dead zone, and wind direction and force explained 85% of the difference between DZ t and DZ e estimates. These factors affected the detection of the seabed and biased acoustically derived indices of demersal-fish abundance. Text atlantic cod Gadus morhua Newfoundland HighWire Press (Stanford University) Newfoundland ICES Journal of Marine Science 66 6 1364 1369 |
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Articles Mello, L. G. S. Rose, G. A. The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish |
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<qd> Mello, L. G. S., and Rose, G. A. 2009. The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish. – ICES Journal of Marine Science, 66: 1364–1369. </qd>The height of the acoustic dead zone, the region near the seabed where fish cannot be resolved acoustically, was calculated both theoretically (DZ t ) and empirically (DZ e ). The DZ e was based on measurements of depth and trawl geometry from sensors (SCANMAR) mounted on a bottom trawl deployed during a survey off Newfoundland and Labrador in winter 2007. Acoustic data were acquired while trawling, using a 38-kHz echosounder (Simrad EK500) with a hull-mounted transducer. The DZ e was calculated as the difference between the trawl-footrope depth and the corresponding acoustically sensed, seabed depth. EK500 and SCANMAR estimates of seabed depth were significantly different. The fish caught were mostly Atlantic cod ( Gadus morhua ). The estimates of DZ e ranged between 2.0 and 3.5 m and were greater than DZ t by 0.1–0.9 m in more than half the cases. Three values of acoustically derived cod densities were estimated for each tow, without dead-zone correction and with corrections for DZ t and DZ e . When compared with DZ t corrections, DZ e resulted in negative (6–12%) and positive (9–35%) corrections to cod density. A general linear model revealed that the seabed depth gradient, standard deviation of estimated fish density in the dead zone, and wind direction and force explained 85% of the difference between DZ t and DZ e estimates. These factors affected the detection of the seabed and biased acoustically derived indices of demersal-fish abundance. |
format |
Text |
author |
Mello, L. G. S. Rose, G. A. |
author_facet |
Mello, L. G. S. Rose, G. A. |
author_sort |
Mello, L. G. S. |
title |
The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish |
title_short |
The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish |
title_full |
The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish |
title_fullStr |
The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish |
title_full_unstemmed |
The acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish |
title_sort |
acoustic dead zone: theoretical vs. empirical estimates, and its effect on density measurements of semi-demersal fish |
publisher |
Oxford University Press |
publishDate |
2009 |
url |
http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1364 https://doi.org/10.1093/icesjms/fsp099 |
geographic |
Newfoundland |
geographic_facet |
Newfoundland |
genre |
atlantic cod Gadus morhua Newfoundland |
genre_facet |
atlantic cod Gadus morhua Newfoundland |
op_relation |
http://icesjms.oxfordjournals.org/cgi/content/short/66/6/1364 http://dx.doi.org/10.1093/icesjms/fsp099 |
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/fsp099 |
container_title |
ICES Journal of Marine Science |
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66 |
container_issue |
6 |
container_start_page |
1364 |
op_container_end_page |
1369 |
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1766358158211547136 |