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Marine Ecology Progress Series

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MEPS 342:291-301 (2007)  -  doi:10.3354/meps342291

Fatty acid signatures and stable isotopes as dietary indicators in North Sea seabirds

Anne Käkelä1, Robert W. Furness2, Andrew Kelly3,4, Ursula Strandberg1, Susan Waldron3,5, Reijo Käkelä1,*

1Faculty of Biosciences, University of Joensuu, PO Box 111, 80101 Joensuu, Finland
2Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow, G12 8QQ, UK
3Scottish Universities Environmental Research Centre, Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, G75 0QF, UK
4Present address: RSPCA, Stapeley Grange Wildlife Centre, London Road, Nantwich, Cheshire CW5 7JW, UK
5Present address: Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK
*Corresponding author. Email:

ABSTRACT: Fatty acid signatures (FAS) of plasma and stable isotopes of carbon (δ13C) and nitrogen (δ15N) of red blood cells were determined in northern gannets Morus bassanus, great skuas Stercorarius skua, shags Phalacrocorax aristotelis, and common guillemots Uria aalge from colonies in the North Sea (collected 2002 to 2003) in order to compare foraging ecologies, and especially to assess the extent to which birds feed on demersal or pelagic prey. The biochemical markers in great skua and gannet indicated that these species feed at a relatively high trophic level, and high variance, especially in great skua, demonstrated either a wide range of food types, individual dietary specialisation or both. The biochemical markers suggested that demersal fish are important constituents of great skua and gannet diets, and thus changes in fisheries discard rates probably influence these populations. In contrast, clear pelagic characteristics and low variance in the markers showed that the diet of common guillemots and shags is pelagic and varies little in composition. Comparison with the reference FAS data for North Sea fish confirmed the dependence of common guillemots on few shoaling pelagic species of fish, probably mainly young sandeels Ammodytes marinus.

KEY WORDS: Fatty acid signatures · Stable isotopes · Fisheries · Foraging ecology · Common murre · Seabirds · North Sea

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