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Marine Ecology Progress Series

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MEPS 380:271-286 (2009)  -  DOI:

Milk fatty acids predict the foraging locations of the New Zealand fur seal: continental shelf versus oceanic waters

Alastair M. M. Baylis1,2,5*, Peter D. Nichols3,4

1School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
2South Australian Research and Development Institute (Aquatic Sciences), PO Box 120, Henley Beach, Adelaide, South Australia 5022, Australia
3CSIRO Marine and Atmospheric Research, Food Futures Flagship, GPO Box 1538, Hobart, Tasmania 7001, Australia
4Antarctic and Climate Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Tasmania 7001, Australia
5Present address: Falkland Islands Government, Fisheries Department, PO Box 598, Stanley, Falkland Islands

ABSTRACT: Lactating New Zealand fur seals Arctocephalus forsteri utilise 2 ecological regions: continental shelf habitats and oceanic habitats associated with the Subtropical Front. Using milk fatty acids (FA) obtained from 29 satellite-tracked fur seals, we characterised the FA composition of seals that foraged on the continental shelf, and those that foraged in oceanic waters. Seals that foraged within oceanic waters were characterised by milk being comparatively high in monounsaturated fatty acids (MUFA; 47.4 ± 4.4%, mean ± SD), and lower in polyunsaturated fatty acids (PUFA; 23.8 ± 4.0%) when compared to seals that foraged in continental shelf waters (MUFA 36.7 ± 5.4 and PUFA 31.4 ± 5.5%). Based on FA compositions, we predicted the likelihood that milk samples collected at random (n = 131) represented individual seals having foraged either on the continental shelf or in distant oceanic waters. Results indicated that 74% (n = 97) of seals were likely to have foraged in oceanic waters, with 26% (n = 34) likely to have foraged within continental shelf waters. These results were supported by the small sub-sample of 29 satellite-tracked seals, which indicated that 62% of seals had foraged in oceanic waters. FA analysis and satellite-tracking results contrasted with scat analyses, from which only 7% of scats contained prey remains from oceanic waters. The results suggest scats were biased toward females foraging on the continental shelf. To further understand the diet of New Zealand fur seals, additional information on potential prey species that inhabit waters associated with the Subtropical Front south of Australia is required, as well as the continued development and application of alternative dietary techniques.

KEY WORDS: Milk fatty acids · New Zealand fur seal · Subtropical Front · Continental shelf

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Cite this article as: Baylis AMM, Nichols PD (2009) Milk fatty acids predict the foraging locations of the New Zealand fur seal: continental shelf versus oceanic waters. Mar Ecol Prog Ser 380:271-286.

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