Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999
<qd> Cox, M. J., Watkins, J. L., Reid, K., and Brierley, A. S. 2011. Spatial and temporal variability in the structure of aggregations of Antarctic krill ( Euphausia superba ) around South Georgia, 1997–1999. – ICES Journal of Marine Science, 68: . </qd>Antarctic krill are important in t...
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fthighwire:oai:open-archive.highwire.org:icesjms:68/3/489 2023-05-15T13:56:13+02:00 Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999 Cox, Martin J. Watkins, Jonathan L. Reid, Keith Brierley, Andrew S. 2011-03-01 00:00:00.0 text/html http://icesjms.oxfordjournals.org/cgi/content/short/68/3/489 https://doi.org/10.1093/icesjms/fsq202 en eng Oxford University Press http://icesjms.oxfordjournals.org/cgi/content/short/68/3/489 http://dx.doi.org/10.1093/icesjms/fsq202 Copyright (C) 2011, International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer Articles TEXT 2011 fthighwire https://doi.org/10.1093/icesjms/fsq202 2011-03-13T13:37:15Z <qd> Cox, M. J., Watkins, J. L., Reid, K., and Brierley, A. S. 2011. Spatial and temporal variability in the structure of aggregations of Antarctic krill ( Euphausia superba ) around South Georgia, 1997–1999. – ICES Journal of Marine Science, 68: . </qd>Antarctic krill are important in the South Georgia (54°S 35°W) marine ecosystem. They form aggregations that vary widely in packing density (<1 to 1000 s of individuals m−3), length (tens to thousands of metres), and height (tens of metres). Acoustic surveys are often used to estimate krill biomass and provide data that give insight into aggregation structure. Using dual-frequency (38 and 120 kHz) acoustic data collected during six surveys conducted around South Georgia during the 1997, 1998, and 1999 austral summers, we isolated 2990 aggregations by applying the Shoal Analysis and Patch Estimation System algorithm in Echoview and a krill-length-dependent acoustic identifier (Δ S v 120–38 ). Multivariate cluster (partition) analysis was applied to metrics from each of the aggregations, resulting in three aggregation types with an overall proportional split of 0.28:0.28:0.44. Types 1 and 3 had low mean densities (<2 g m−3), whereas Type 2 had a mean density of 94 g m−3. Intersurvey differences were found between the effort-corrected numbers of aggregation types ( p = 2.5e−6), and between on- and off-continental shelf areas ( p = 1.5e−7), with a greater number of Type 2 aggregations being found on-shelf. The findings suggest intersurvey variation in krill catchability, with krill being more likely to be caught on-shelf. Text Antarc* Antarctic Antarctic Krill Euphausia superba HighWire Press (Stanford University) Antarctic Austral Watkins ENVELOPE(-67.086,-67.086,-66.354,-66.354) ICES Journal of Marine Science 68 3 489 498 |
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HighWire Press (Stanford University) |
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English |
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Articles |
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Articles Cox, Martin J. Watkins, Jonathan L. Reid, Keith Brierley, Andrew S. Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999 |
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description |
<qd> Cox, M. J., Watkins, J. L., Reid, K., and Brierley, A. S. 2011. Spatial and temporal variability in the structure of aggregations of Antarctic krill ( Euphausia superba ) around South Georgia, 1997–1999. – ICES Journal of Marine Science, 68: . </qd>Antarctic krill are important in the South Georgia (54°S 35°W) marine ecosystem. They form aggregations that vary widely in packing density (<1 to 1000 s of individuals m−3), length (tens to thousands of metres), and height (tens of metres). Acoustic surveys are often used to estimate krill biomass and provide data that give insight into aggregation structure. Using dual-frequency (38 and 120 kHz) acoustic data collected during six surveys conducted around South Georgia during the 1997, 1998, and 1999 austral summers, we isolated 2990 aggregations by applying the Shoal Analysis and Patch Estimation System algorithm in Echoview and a krill-length-dependent acoustic identifier (Δ S v 120–38 ). Multivariate cluster (partition) analysis was applied to metrics from each of the aggregations, resulting in three aggregation types with an overall proportional split of 0.28:0.28:0.44. Types 1 and 3 had low mean densities (<2 g m−3), whereas Type 2 had a mean density of 94 g m−3. Intersurvey differences were found between the effort-corrected numbers of aggregation types ( p = 2.5e−6), and between on- and off-continental shelf areas ( p = 1.5e−7), with a greater number of Type 2 aggregations being found on-shelf. The findings suggest intersurvey variation in krill catchability, with krill being more likely to be caught on-shelf. |
format |
Text |
author |
Cox, Martin J. Watkins, Jonathan L. Reid, Keith Brierley, Andrew S. |
author_facet |
Cox, Martin J. Watkins, Jonathan L. Reid, Keith Brierley, Andrew S. |
author_sort |
Cox, Martin J. |
title |
Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999 |
title_short |
Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999 |
title_full |
Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999 |
title_fullStr |
Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999 |
title_full_unstemmed |
Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997-1999 |
title_sort |
spatial and temporal variability in the structure of aggregations of antarctic krill (euphausia superba) around south georgia, 1997-1999 |
publisher |
Oxford University Press |
publishDate |
2011 |
url |
http://icesjms.oxfordjournals.org/cgi/content/short/68/3/489 https://doi.org/10.1093/icesjms/fsq202 |
long_lat |
ENVELOPE(-67.086,-67.086,-66.354,-66.354) |
geographic |
Antarctic Austral Watkins |
geographic_facet |
Antarctic Austral Watkins |
genre |
Antarc* Antarctic Antarctic Krill Euphausia superba |
genre_facet |
Antarc* Antarctic Antarctic Krill Euphausia superba |
op_relation |
http://icesjms.oxfordjournals.org/cgi/content/short/68/3/489 http://dx.doi.org/10.1093/icesjms/fsq202 |
op_rights |
Copyright (C) 2011, International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer |
op_doi |
https://doi.org/10.1093/icesjms/fsq202 |
container_title |
ICES Journal of Marine Science |
container_volume |
68 |
container_issue |
3 |
container_start_page |
489 |
op_container_end_page |
498 |
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1766263579551465472 |