Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia
South Georgia is renowned for the abundance of Antarctic krill (Euphausia superba) and a range of krill predators. Variability in krill availability at a range of scales, and the consequences of this for predator-prey interactions, mean that quantifying the spatially explicit demand for krill by tho...
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University of St Andrews
2007
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ftstandrewserep:oai:research-repository.st-andrews.ac.uk:10023/335 2023-07-02T03:30:27+02:00 Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia Swarbrick, Matthew Lewis Boyd, Ian Reid, Keith Trathan, Phil N. 224 2007-05-31T08:25:01Z 7257498 bytes application/pdf http://hdl.handle.net/10023/335 en eng University of St Andrews The University of St Andrews British Antarctic Survey uk.bl.ethos.552006 http://hdl.handle.net/10023/335 South Georgia Antarctic fur seal Krill Euphausia superba Predator-prey Arctocephalus gazella Distribution Demand Macaroni penguin Eudyptes chrysolophus QH132.S644S8 Euphausia superba--Predators of--South Georgia Island Animal population density--South Georgia Island Marine ecology--South Georgia Island Euphausia superba--South Georgia Island Thesis Doctoral PhD Doctor of Philosophy 2007 ftstandrewserep 2023-06-13T18:29:43Z South Georgia is renowned for the abundance of Antarctic krill (Euphausia superba) and a range of krill predators. Variability in krill availability at a range of scales, and the consequences of this for predator-prey interactions, mean that quantifying the spatially explicit demand for krill by those predators is essential to understanding the mechanisms underlying ecosystem changes in the region. In this thesis demand within a distinct study box to the northwest of the island has been assessed. The thesis has three sections; (1) the number of predators; (2) the distribution of predators; and (3) the demand for krill by those predators. (1) Predator densities with confidence intervals were determined from appropriately designed shipboard transect survey; counts of Antarctic fur seals (Arctocephalus gazella), macaroni penguins (Eudyptes chrysolophus), gentoo penguins (Pygoscelis papua), and Antarctic prions (Pachyptila desolata) were adjusted for sea state, distance from observer and dive behaviour. Providing the first at-sea predator density estimates for the region. (2) A comparison of the distribution of female Antarctic fur seals engaged in pup-rearing (using satellite telemetry) and the whole population that were not restricted to a single part of the population (from shipboard transect survey) was undertaken. Using two general additive models based on the relationship between seal distribution (one derived from transect and the other from telemetry) and the physical environment indicated that the spatial distribution of lactating females is representative of the general population. (3) Using the derived predator density, the local krill demand estimate was 2581 tonnes krill per day, a consumption rate of 0.45% per day of the concurrently estimated krill biomass (using shipboard acoustics). Antarctic fur seals accounted for 75% of this demand. This level of demand was less than the increase in biomass resulting from krill growth. However, based on the length-specific demand, determined from concurrent ... Doctoral or Postdoctoral Thesis Antarc* Antarctic Antarctic Fur Seal Antarctic Fur Seals Antarctic Krill Arctocephalus gazella Eudyptes chrysolophus Euphausia superba Macaroni penguin Pachyptila desolata Pygoscelis papua South Georgia Island University of St Andrews: Digital Research Repository Antarctic South Georgia Island ENVELOPE(-36.750,-36.750,-54.250,-54.250) |
institution |
Open Polar |
collection |
University of St Andrews: Digital Research Repository |
op_collection_id |
ftstandrewserep |
language |
English |
topic |
South Georgia Antarctic fur seal Krill Euphausia superba Predator-prey Arctocephalus gazella Distribution Demand Macaroni penguin Eudyptes chrysolophus QH132.S644S8 Euphausia superba--Predators of--South Georgia Island Animal population density--South Georgia Island Marine ecology--South Georgia Island Euphausia superba--South Georgia Island |
spellingShingle |
South Georgia Antarctic fur seal Krill Euphausia superba Predator-prey Arctocephalus gazella Distribution Demand Macaroni penguin Eudyptes chrysolophus QH132.S644S8 Euphausia superba--Predators of--South Georgia Island Animal population density--South Georgia Island Marine ecology--South Georgia Island Euphausia superba--South Georgia Island Swarbrick, Matthew Lewis Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia |
topic_facet |
South Georgia Antarctic fur seal Krill Euphausia superba Predator-prey Arctocephalus gazella Distribution Demand Macaroni penguin Eudyptes chrysolophus QH132.S644S8 Euphausia superba--Predators of--South Georgia Island Animal population density--South Georgia Island Marine ecology--South Georgia Island Euphausia superba--South Georgia Island |
description |
South Georgia is renowned for the abundance of Antarctic krill (Euphausia superba) and a range of krill predators. Variability in krill availability at a range of scales, and the consequences of this for predator-prey interactions, mean that quantifying the spatially explicit demand for krill by those predators is essential to understanding the mechanisms underlying ecosystem changes in the region. In this thesis demand within a distinct study box to the northwest of the island has been assessed. The thesis has three sections; (1) the number of predators; (2) the distribution of predators; and (3) the demand for krill by those predators. (1) Predator densities with confidence intervals were determined from appropriately designed shipboard transect survey; counts of Antarctic fur seals (Arctocephalus gazella), macaroni penguins (Eudyptes chrysolophus), gentoo penguins (Pygoscelis papua), and Antarctic prions (Pachyptila desolata) were adjusted for sea state, distance from observer and dive behaviour. Providing the first at-sea predator density estimates for the region. (2) A comparison of the distribution of female Antarctic fur seals engaged in pup-rearing (using satellite telemetry) and the whole population that were not restricted to a single part of the population (from shipboard transect survey) was undertaken. Using two general additive models based on the relationship between seal distribution (one derived from transect and the other from telemetry) and the physical environment indicated that the spatial distribution of lactating females is representative of the general population. (3) Using the derived predator density, the local krill demand estimate was 2581 tonnes krill per day, a consumption rate of 0.45% per day of the concurrently estimated krill biomass (using shipboard acoustics). Antarctic fur seals accounted for 75% of this demand. This level of demand was less than the increase in biomass resulting from krill growth. However, based on the length-specific demand, determined from concurrent ... |
author2 |
Boyd, Ian Reid, Keith Trathan, Phil N. |
format |
Doctoral or Postdoctoral Thesis |
author |
Swarbrick, Matthew Lewis |
author_facet |
Swarbrick, Matthew Lewis |
author_sort |
Swarbrick, Matthew Lewis |
title |
Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia |
title_short |
Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia |
title_full |
Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia |
title_fullStr |
Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia |
title_full_unstemmed |
Estimating the distribution of demand for Antarctic krill (Euphauisa superba) from land-based predators at South Georgia |
title_sort |
estimating the distribution of demand for antarctic krill (euphauisa superba) from land-based predators at south georgia |
publisher |
University of St Andrews |
publishDate |
2007 |
url |
http://hdl.handle.net/10023/335 |
op_coverage |
224 |
long_lat |
ENVELOPE(-36.750,-36.750,-54.250,-54.250) |
geographic |
Antarctic South Georgia Island |
geographic_facet |
Antarctic South Georgia Island |
genre |
Antarc* Antarctic Antarctic Fur Seal Antarctic Fur Seals Antarctic Krill Arctocephalus gazella Eudyptes chrysolophus Euphausia superba Macaroni penguin Pachyptila desolata Pygoscelis papua South Georgia Island |
genre_facet |
Antarc* Antarctic Antarctic Fur Seal Antarctic Fur Seals Antarctic Krill Arctocephalus gazella Eudyptes chrysolophus Euphausia superba Macaroni penguin Pachyptila desolata Pygoscelis papua South Georgia Island |
op_relation |
uk.bl.ethos.552006 http://hdl.handle.net/10023/335 |
_version_ |
1770274645849669632 |