Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity
Dual frequency (38 and 120 kHz) acoustic surveys of shelf-break regions in the vicinity of the Willis Islands, South Georgia, and Coronation Island, South Orkneys, both in the Atlantic sector of the Southern Ocean, were carried out from RRS 'James Clark Ross' during January 1994. The diffe...
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Online Access: | https://risweb.st-andrews.ac.uk/portal/en/researchoutput/acoustic-targets-at-south-georgia-and-the-south-orkney-islands-during-a-season-of-krill-scarcity(0290f518-da96-4ba8-a4e6-3fd055b0a927).html http://www.scopus.com/inward/record.url?scp=0029669567&partnerID=8YFLogxK |
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ftunstandrewcris:oai:risweb.st-andrews.ac.uk:publications/0290f518-da96-4ba8-a4e6-3fd055b0a927 2023-05-15T13:45:52+02:00 Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity Brierley, Andrew Stuart Watkins, JL 1996-07 https://risweb.st-andrews.ac.uk/portal/en/researchoutput/acoustic-targets-at-south-georgia-and-the-south-orkney-islands-during-a-season-of-krill-scarcity(0290f518-da96-4ba8-a4e6-3fd055b0a927).html http://www.scopus.com/inward/record.url?scp=0029669567&partnerID=8YFLogxK eng eng info:eu-repo/semantics/restrictedAccess Brierley , A S & Watkins , JL 1996 , ' Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity ' , Marine Ecology Progress Series , vol. 138 , no. 1-3 , pp. 51-61 . Antarctic krill Euphausia superba dual frequency acoustic survey predators penguin diet Themisto gaudichaudii target discrimination Southern Ocean EUPHAUSIA-SUPERBA DANA ANTARCTIC FUR SEALS VERTICAL MIGRATION CHINSTRAP PENGUINS SIGNY ISLAND BIRD-ISLAND SWARMS VARIABILITY AVOIDANCE BIOMASS article 1996 ftunstandrewcris 2021-12-26T14:10:56Z Dual frequency (38 and 120 kHz) acoustic surveys of shelf-break regions in the vicinity of the Willis Islands, South Georgia, and Coronation Island, South Orkneys, both in the Atlantic sector of the Southern Ocean, were carried out from RRS 'James Clark Ross' during January 1994. The difference in echo signal strength between the 2 frequencies [delta MVBS (mean volume backscattering strength) = MVBS 120 kHz - MVBS 38 kHz] was used to partition acoustic targets into 3 biological categories: Antarctic krill Euphausia superba, nekton (larger than krill) and zooplankton (smaller than krill). Krill density estimates were derived for both survey areas, and the relative contribution of each class of target to overall regional pelagic biomass determined. Krill distribution in both regions was extremely patchy, resulting in a highly skewed frequency distribution of density; for example one echo-integration interval contained 10(4) times the mean krill density. An approximate B-fold difference in mean krill abundance was detected between the 2 areas but, in comparison with previously published density estimates, krill densities in both regions were extremely low (1.7 and 10.7 gm(-2) for Willis and Coronation Islands respectively). Gross regional differences in pelagic faunal composition were apparent ent from inspection of echo charts, and were quantified by detailed analysis of acoustic signals. The water column in the vicinity of the Willis Islands was characterised by a series of diffuse but continuous scattering layers visible only at 120 kHz, and 73% by mass of acoustic targets in this region were classified as zooplankton. In marked contrast, the Coronation Island region was dominated by dense, discrete acoustic target patches which were classified as larger, nektonic, sound scatterers (fish or squid), and only 12% of targets there were classified as zooplankton. Elsewhere, data from predator diet analyses carried out at Bird Island, South Georgia, during the same season that our acoustic measurements were made, ... Article in Journal/Newspaper Antarc* Antarctic Antarctic Fur Seals Antarctic Krill Bird Island Coronation Island Euphausia superba Signy Island South Orkney Islands Southern Ocean Willis Islands University of St Andrews: Research Portal Antarctic Southern Ocean South Orkney Islands ENVELOPE(-45.500,-45.500,-60.583,-60.583) Bird Island ENVELOPE(-38.060,-38.060,-54.004,-54.004) Signy Island ENVELOPE(-45.595,-45.595,-60.708,-60.708) Willis ENVELOPE(159.450,159.450,-79.367,-79.367) Coronation Island ENVELOPE(-45.588,-45.588,-60.595,-60.595) Willis Islands ENVELOPE(-38.195,-38.195,-54.001,-54.001) |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
Antarctic krill Euphausia superba dual frequency acoustic survey predators penguin diet Themisto gaudichaudii target discrimination Southern Ocean EUPHAUSIA-SUPERBA DANA ANTARCTIC FUR SEALS VERTICAL MIGRATION CHINSTRAP PENGUINS SIGNY ISLAND BIRD-ISLAND SWARMS VARIABILITY AVOIDANCE BIOMASS |
spellingShingle |
Antarctic krill Euphausia superba dual frequency acoustic survey predators penguin diet Themisto gaudichaudii target discrimination Southern Ocean EUPHAUSIA-SUPERBA DANA ANTARCTIC FUR SEALS VERTICAL MIGRATION CHINSTRAP PENGUINS SIGNY ISLAND BIRD-ISLAND SWARMS VARIABILITY AVOIDANCE BIOMASS Brierley, Andrew Stuart Watkins, JL Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity |
topic_facet |
Antarctic krill Euphausia superba dual frequency acoustic survey predators penguin diet Themisto gaudichaudii target discrimination Southern Ocean EUPHAUSIA-SUPERBA DANA ANTARCTIC FUR SEALS VERTICAL MIGRATION CHINSTRAP PENGUINS SIGNY ISLAND BIRD-ISLAND SWARMS VARIABILITY AVOIDANCE BIOMASS |
description |
Dual frequency (38 and 120 kHz) acoustic surveys of shelf-break regions in the vicinity of the Willis Islands, South Georgia, and Coronation Island, South Orkneys, both in the Atlantic sector of the Southern Ocean, were carried out from RRS 'James Clark Ross' during January 1994. The difference in echo signal strength between the 2 frequencies [delta MVBS (mean volume backscattering strength) = MVBS 120 kHz - MVBS 38 kHz] was used to partition acoustic targets into 3 biological categories: Antarctic krill Euphausia superba, nekton (larger than krill) and zooplankton (smaller than krill). Krill density estimates were derived for both survey areas, and the relative contribution of each class of target to overall regional pelagic biomass determined. Krill distribution in both regions was extremely patchy, resulting in a highly skewed frequency distribution of density; for example one echo-integration interval contained 10(4) times the mean krill density. An approximate B-fold difference in mean krill abundance was detected between the 2 areas but, in comparison with previously published density estimates, krill densities in both regions were extremely low (1.7 and 10.7 gm(-2) for Willis and Coronation Islands respectively). Gross regional differences in pelagic faunal composition were apparent ent from inspection of echo charts, and were quantified by detailed analysis of acoustic signals. The water column in the vicinity of the Willis Islands was characterised by a series of diffuse but continuous scattering layers visible only at 120 kHz, and 73% by mass of acoustic targets in this region were classified as zooplankton. In marked contrast, the Coronation Island region was dominated by dense, discrete acoustic target patches which were classified as larger, nektonic, sound scatterers (fish or squid), and only 12% of targets there were classified as zooplankton. Elsewhere, data from predator diet analyses carried out at Bird Island, South Georgia, during the same season that our acoustic measurements were made, ... |
format |
Article in Journal/Newspaper |
author |
Brierley, Andrew Stuart Watkins, JL |
author_facet |
Brierley, Andrew Stuart Watkins, JL |
author_sort |
Brierley, Andrew Stuart |
title |
Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity |
title_short |
Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity |
title_full |
Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity |
title_fullStr |
Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity |
title_full_unstemmed |
Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity |
title_sort |
acoustic targets at south georgia and the south orkney islands during a season of krill scarcity |
publishDate |
1996 |
url |
https://risweb.st-andrews.ac.uk/portal/en/researchoutput/acoustic-targets-at-south-georgia-and-the-south-orkney-islands-during-a-season-of-krill-scarcity(0290f518-da96-4ba8-a4e6-3fd055b0a927).html http://www.scopus.com/inward/record.url?scp=0029669567&partnerID=8YFLogxK |
long_lat |
ENVELOPE(-45.500,-45.500,-60.583,-60.583) ENVELOPE(-38.060,-38.060,-54.004,-54.004) ENVELOPE(-45.595,-45.595,-60.708,-60.708) ENVELOPE(159.450,159.450,-79.367,-79.367) ENVELOPE(-45.588,-45.588,-60.595,-60.595) ENVELOPE(-38.195,-38.195,-54.001,-54.001) |
geographic |
Antarctic Southern Ocean South Orkney Islands Bird Island Signy Island Willis Coronation Island Willis Islands |
geographic_facet |
Antarctic Southern Ocean South Orkney Islands Bird Island Signy Island Willis Coronation Island Willis Islands |
genre |
Antarc* Antarctic Antarctic Fur Seals Antarctic Krill Bird Island Coronation Island Euphausia superba Signy Island South Orkney Islands Southern Ocean Willis Islands |
genre_facet |
Antarc* Antarctic Antarctic Fur Seals Antarctic Krill Bird Island Coronation Island Euphausia superba Signy Island South Orkney Islands Southern Ocean Willis Islands |
op_source |
Brierley , A S & Watkins , JL 1996 , ' Acoustic targets at South Georgia and the South Orkney Islands during a season of krill scarcity ' , Marine Ecology Progress Series , vol. 138 , no. 1-3 , pp. 51-61 . |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766231843505438720 |