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Quantifying the trophic linkages of Antarctic marine predators

Quantifying the trophic linkages of Antarctic marine predators
Andrea Walters

Authors

A Walters
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania, Australia
Antarctic and Climate Ecosystems Cooperative Research Centre, Private Bag 80, Hobart, Tasmania, Australia

MA. Lea
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania, Australia

M Bester
Department of Zoology and Entomology, University of Pretoria, South Africa

M Goebel
NOAA South West Fisheries Science Centre, North Torrey Pines Court, La Jolla, USA

P Trathan
British Antarctic Survey, Madingley Rd, High Cross, Cambridge, UK

G Miller
Division of Pathology and Laboratory Medicine, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia

S Sokolov
CSIRO Marine and Atmospheric Research, Castray Esplanade, Hobart, Tasmania, Australia

J van den Hoff
Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania, Australia

C Oosthuizen
Department of Zoology and Entomology, University of Pretoria, South Africa

M Hindell
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania, Australia

Abstract

We assessed the trophic relationships of Antarctic fur seals (Arctocephalus gazella), southern elephant seals (Mirounga leonina)and emperor penguins (Aptenodytes forsteri)by analysing variation in stable isotope values along the length of seal whiskers and in whole blood. Whisker isotopic data, mixing models and concurrent tracking information for fur seals (2008 and 2009) and elephant seals (1995, 1999 and 2005) showed how seals, which breed on opposite sides of the Polar Front (PF), exhibit contrasting winter movement behaviour to access predictable, high food source areas during winter. In the Western Antarctica Peninsula (WAP), fur seals (n=24) migrated north to oceanic waters. Isotopic mixing models estimated the relative proportion and diversity of fish and squid prey to the diets of seals increased from areas close to the WAP in autumn (39.1%) to waters north of the Subantarctic Front (SAF) in spring (84.2%) where no Antarctic krill occurs. In contrast, fur seals in the Indian Sector (Marion Is., n=19) and elephant seals in the Pacific Sector (Macquarie Is., n=23) travelled south towards Antarctica. Some fur seals travelled to the ice edge, with model estimates indicating consumption of crustaceans, such as Antarctic krill (20.9%), in addition to mesopelagic fish and squid (49.6%) in PF and SAF waters. Stable isotope ratios for blood reflected the use of high Antarctic waters by breeding and chick rearing penguins from the Auster colony, Mawson Coast, Antarctica in 2008 (n=156). The isotopic signature of females indicated increased importance of higher trophic level prey (fish and squid) from early to mid-winter, concurrent with a shift in δ15N from 11.2 to 11.8‰. In spring, adults and chicks were segregated by their δ15N signatures indicating adults consumed crustaceans, fish and squid (10.6‰), but fed higher trophic level prey (fish and squid) to their young (11.4‰).

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  • 11th June 2013
    Registrations close
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    Conference commences
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    Conference concludes

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This page was last modified on 24 September 2013.