Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill
Upward-looking acoustic Doppler current profilers (ADCPs) (300 kHz) and echosounders (125 kHz) were deployed on moorings at South Georgia to measure abundance of Antarctic krill continuously over several months. Echoes from krill were identified using the theoretical difference in echo intensity at...
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ftunstandrewcris:oai:risweb.st-andrews.ac.uk:publications/3aee93d2-c287-4cce-bd49-a43cf32de444 2023-05-15T13:47:48+02:00 Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill Brierley, Andrew Stuart Saunders, RA Bone, DG Murphy, EJ 2006-02 https://risweb.st-andrews.ac.uk/portal/en/researchoutput/use-of-moored-acoustic-instruments-to-measure-shortterm-variability-in-abundance-of-antarctic-krill(3aee93d2-c287-4cce-bd49-a43cf32de444).html eng eng info:eu-repo/semantics/restrictedAccess Brierley , A S , Saunders , RA , Bone , DG & Murphy , EJ 2006 , ' Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill ' , Limnology and Oceanography: Methods , vol. 4 , pp. 18-29 . DOPPLER CURRENT PROFILER DIEL VERTICAL MIGRATION SOUTH GEORGIA EUPHAUSIA-SUPERBA INTERANNUAL VARIABILITY TARGET-STRENGTH SCOTIA SEA TEMPORAL VARIABILITY SEASONAL-VARIATION MARINE ECOSYSTEM article 2006 ftunstandrewcris 2021-12-26T14:14:20Z Upward-looking acoustic Doppler current profilers (ADCPs) (300 kHz) and echosounders (125 kHz) were deployed on moorings at South Georgia to measure abundance of Antarctic krill continuously over several months. Echoes from krill were identified using the theoretical difference in echo intensity at 300 and 125 kHz and scaled to krill density using target strengths appropriate for krill in the region: krill size was determined from diet samples from furseals and penguins foraging near the moorings. A method using water flow past the moorings was developed to convert time-based acoustic observations of krill to area-based abundance estimates. Flow past the stationary moorings was treated analogously to motion along-track of a research vessel through a nominally stationary body of water during a conventional survey. The moorings thus provide a Eulerian view of variation in krill abundance. This is ecologically instructive for South Georgia, where krill are generally passive drifters on currents and where temporal fluctuations in abundance have significant consequences for krill-dependent predators. Moorings were positioned on routine research vessel survey transects, and validity of the mooring method was assessed by comparison of mooring and vessel observations. Krill density estimates from the moorings were not statistically different from vessel estimates in adjacent time periods. A time series of krill density from a mooring revealed step-changes that were not seen during short-term vessel surveys. Moorings deliver data over time scales that cannot be achieved from research vessels and provide insight on environmental factors associated with variation in krill abundance at South Georgia. Mooring data may aid ecosystem-based management. Article in Journal/Newspaper Antarc* Antarctic Antarctic Krill Euphausia superba Scotia Sea University of St Andrews: Research Portal Antarctic Scotia Sea |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
DOPPLER CURRENT PROFILER DIEL VERTICAL MIGRATION SOUTH GEORGIA EUPHAUSIA-SUPERBA INTERANNUAL VARIABILITY TARGET-STRENGTH SCOTIA SEA TEMPORAL VARIABILITY SEASONAL-VARIATION MARINE ECOSYSTEM |
spellingShingle |
DOPPLER CURRENT PROFILER DIEL VERTICAL MIGRATION SOUTH GEORGIA EUPHAUSIA-SUPERBA INTERANNUAL VARIABILITY TARGET-STRENGTH SCOTIA SEA TEMPORAL VARIABILITY SEASONAL-VARIATION MARINE ECOSYSTEM Brierley, Andrew Stuart Saunders, RA Bone, DG Murphy, EJ Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill |
topic_facet |
DOPPLER CURRENT PROFILER DIEL VERTICAL MIGRATION SOUTH GEORGIA EUPHAUSIA-SUPERBA INTERANNUAL VARIABILITY TARGET-STRENGTH SCOTIA SEA TEMPORAL VARIABILITY SEASONAL-VARIATION MARINE ECOSYSTEM |
description |
Upward-looking acoustic Doppler current profilers (ADCPs) (300 kHz) and echosounders (125 kHz) were deployed on moorings at South Georgia to measure abundance of Antarctic krill continuously over several months. Echoes from krill were identified using the theoretical difference in echo intensity at 300 and 125 kHz and scaled to krill density using target strengths appropriate for krill in the region: krill size was determined from diet samples from furseals and penguins foraging near the moorings. A method using water flow past the moorings was developed to convert time-based acoustic observations of krill to area-based abundance estimates. Flow past the stationary moorings was treated analogously to motion along-track of a research vessel through a nominally stationary body of water during a conventional survey. The moorings thus provide a Eulerian view of variation in krill abundance. This is ecologically instructive for South Georgia, where krill are generally passive drifters on currents and where temporal fluctuations in abundance have significant consequences for krill-dependent predators. Moorings were positioned on routine research vessel survey transects, and validity of the mooring method was assessed by comparison of mooring and vessel observations. Krill density estimates from the moorings were not statistically different from vessel estimates in adjacent time periods. A time series of krill density from a mooring revealed step-changes that were not seen during short-term vessel surveys. Moorings deliver data over time scales that cannot be achieved from research vessels and provide insight on environmental factors associated with variation in krill abundance at South Georgia. Mooring data may aid ecosystem-based management. |
format |
Article in Journal/Newspaper |
author |
Brierley, Andrew Stuart Saunders, RA Bone, DG Murphy, EJ |
author_facet |
Brierley, Andrew Stuart Saunders, RA Bone, DG Murphy, EJ |
author_sort |
Brierley, Andrew Stuart |
title |
Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill |
title_short |
Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill |
title_full |
Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill |
title_fullStr |
Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill |
title_full_unstemmed |
Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill |
title_sort |
use of moored acoustic instruments to measure short-term variability in abundance of antarctic krill |
publishDate |
2006 |
url |
https://risweb.st-andrews.ac.uk/portal/en/researchoutput/use-of-moored-acoustic-instruments-to-measure-shortterm-variability-in-abundance-of-antarctic-krill(3aee93d2-c287-4cce-bd49-a43cf32de444).html |
geographic |
Antarctic Scotia Sea |
geographic_facet |
Antarctic Scotia Sea |
genre |
Antarc* Antarctic Antarctic Krill Euphausia superba Scotia Sea |
genre_facet |
Antarc* Antarctic Antarctic Krill Euphausia superba Scotia Sea |
op_source |
Brierley , A S , Saunders , RA , Bone , DG & Murphy , EJ 2006 , ' Use of moored acoustic instruments to measure short-term variability in abundance of Antarctic krill ' , Limnology and Oceanography: Methods , vol. 4 , pp. 18-29 . |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766247901604872192 |