Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density
Upward-looking acoustic Doppler current profilers (300 kHz) and echo sounders (125 kHz) were deployed on moorings on- and off-shelf to the northwest of South Georgia between 14 October 2002 and 29 December 2005 to measure density of Antarctic krill and environmental parameters continuously. A distin...
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ftnerc:oai:nora.nerc.ac.uk:11933 2023-05-15T13:45:10+02:00 Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density Saunders, R.A. Brierley, A.S. Watkins, Jonathan L. Reid, Keith Murphy, Eugene J. Enderlein, Peter Bone, D.G. 2007 http://nora.nerc.ac.uk/id/eprint/11933/ https://www.ccamlr.org/en/publications/science_journal/ccamlr-science-volume-14/ccamlr-science-volume-1427-41 unknown CCAMLR Saunders, R.A.; Brierley, A.S.; Watkins, Jonathan L.; Reid, Keith; Murphy, Eugene J. orcid:0000-0002-7369-9196 Enderlein, Peter; Bone, D.G. 2007 Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density. CCAMLR Science, 14. 27-41. Marine Sciences Zoology Ecology and Environment Publication - Article PeerReviewed 2007 ftnerc 2023-02-04T19:27:39Z Upward-looking acoustic Doppler current profilers (300 kHz) and echo sounders (125 kHz) were deployed on moorings on- and off-shelf to the northwest of South Georgia between 14 October 2002 and 29 December 2005 to measure density of Antarctic krill and environmental parameters continuously. A distinct seasonal pattern in krill density, recurring consistently over all three years, was detected. Krill densities in winter were predominantly low (mean = 18.7 g m(-2), SD = 24.3), but had risen substantially by summer in each year (mean = 89.5 g m(-2), SD = 64.2). A sinusoidal regression model (period = 52 weeks) with time as the independent variable explained 64% of the observed week-to-week variation. Estimates of krill density from moored instruments were not statistically different (P > 0.05) from estimates derived from standard ship-based krill surveys in adjacent time periods, suggesting that the point estimates from moored instruments were representative of krill density in a wider spatial context (ship surveys cover c. 100 x 100 km). Data from moored instruments were used to explore whether high-frequency temporal variation (i.e. within-year) could have led to the perceived between-year variation in krill density arising from previous summer surveys in the South Georgia western core box region between 1990 and 2005. Comparison of these 'snap-shot' ship survey estimates with the observed pattern of within-year variability showed that some of the apparent 'year-to-year' variation could simply be attributed to sampling on different dates of the year (e.g. November cf. February). However, there were some survey estimates that were significantly different (P < 0.01) from the regression-predicted within-year variation. Years that stand out for markedly low krill density (i.e. densities below the range expected due to intra-annual variation) were 1993/94, 1998/99 and 1999/2000. Moored instruments provide valuable data that could be important for ecosystem-based management at South Georgia because, for example, ... Article in Journal/Newspaper Antarc* Antarctic Antarctic Krill Euphausia superba Natural Environment Research Council: NERC Open Research Archive Antarctic |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
unknown |
topic |
Marine Sciences Zoology Ecology and Environment |
spellingShingle |
Marine Sciences Zoology Ecology and Environment Saunders, R.A. Brierley, A.S. Watkins, Jonathan L. Reid, Keith Murphy, Eugene J. Enderlein, Peter Bone, D.G. Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density |
topic_facet |
Marine Sciences Zoology Ecology and Environment |
description |
Upward-looking acoustic Doppler current profilers (300 kHz) and echo sounders (125 kHz) were deployed on moorings on- and off-shelf to the northwest of South Georgia between 14 October 2002 and 29 December 2005 to measure density of Antarctic krill and environmental parameters continuously. A distinct seasonal pattern in krill density, recurring consistently over all three years, was detected. Krill densities in winter were predominantly low (mean = 18.7 g m(-2), SD = 24.3), but had risen substantially by summer in each year (mean = 89.5 g m(-2), SD = 64.2). A sinusoidal regression model (period = 52 weeks) with time as the independent variable explained 64% of the observed week-to-week variation. Estimates of krill density from moored instruments were not statistically different (P > 0.05) from estimates derived from standard ship-based krill surveys in adjacent time periods, suggesting that the point estimates from moored instruments were representative of krill density in a wider spatial context (ship surveys cover c. 100 x 100 km). Data from moored instruments were used to explore whether high-frequency temporal variation (i.e. within-year) could have led to the perceived between-year variation in krill density arising from previous summer surveys in the South Georgia western core box region between 1990 and 2005. Comparison of these 'snap-shot' ship survey estimates with the observed pattern of within-year variability showed that some of the apparent 'year-to-year' variation could simply be attributed to sampling on different dates of the year (e.g. November cf. February). However, there were some survey estimates that were significantly different (P < 0.01) from the regression-predicted within-year variation. Years that stand out for markedly low krill density (i.e. densities below the range expected due to intra-annual variation) were 1993/94, 1998/99 and 1999/2000. Moored instruments provide valuable data that could be important for ecosystem-based management at South Georgia because, for example, ... |
format |
Article in Journal/Newspaper |
author |
Saunders, R.A. Brierley, A.S. Watkins, Jonathan L. Reid, Keith Murphy, Eugene J. Enderlein, Peter Bone, D.G. |
author_facet |
Saunders, R.A. Brierley, A.S. Watkins, Jonathan L. Reid, Keith Murphy, Eugene J. Enderlein, Peter Bone, D.G. |
author_sort |
Saunders, R.A. |
title |
Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density |
title_short |
Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density |
title_full |
Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density |
title_fullStr |
Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density |
title_full_unstemmed |
Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density |
title_sort |
intra-annual variability in the density of antarctic krill (euphausia superba) at south georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density |
publisher |
CCAMLR |
publishDate |
2007 |
url |
http://nora.nerc.ac.uk/id/eprint/11933/ https://www.ccamlr.org/en/publications/science_journal/ccamlr-science-volume-14/ccamlr-science-volume-1427-41 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic Antarctic Krill Euphausia superba |
genre_facet |
Antarc* Antarctic Antarctic Krill Euphausia superba |
op_relation |
Saunders, R.A.; Brierley, A.S.; Watkins, Jonathan L.; Reid, Keith; Murphy, Eugene J. orcid:0000-0002-7369-9196 Enderlein, Peter; Bone, D.G. 2007 Intra-annual variability in the density of Antarctic krill (Euphausia superba) at South Georgia, 2002-2005: within-year variation provides a new framework for interpreting previous 'annual' estimates of krill density. CCAMLR Science, 14. 27-41. |
_version_ |
1766214816989446144 |