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Antarctic fur seals foraging in the Polar Frontal Zone: inter-annual shifts in diet as shown by faecal and fatty acid analyses

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Lea, M-A and Cherel, Y and Guinet, C and Nichols, PD (2002) Antarctic fur seals foraging in the Polar Frontal Zone: inter-annual shifts in diet as shown by faecal and fatty acid analyses. Marine Ecology Progress Series, 245. pp. 281-297. ISSN Print 0171-8630 Online 1616-1599

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Abstract

We studied the dietary preferences of Antarctic fur seals Arctocephalus gazella from Cap
Noir, Îles Kerguelen, foraging in the Antarctic Polar Frontal Zone (PFZ) in February of 1998, 1999 and
2000. Scats were collected and analyzed for remaining prey hard parts in each of the 3 years, and in
1999 and 2000, the fatty acid (FA) composition of fur seal milk samples was also examined for longerterm
dietary preferences. Scat analyses revealed that seals foraged primarily on fish and some squid in
all 3 years with 25 species of fish being taken during the study. Myctophid fish accounted for an average
of 94% by number of all fish consumed with 3 species, Gymnoscopelus nicholsi, G. piabilis and
Electrona subaspera, forming the core diet. Inter-annual differences in dietary species composition
were apparent, however, with the presence of the mackerel icefish Champsocephalus gunnari in 1998
and the myctophid Protomyctophum tenisoni in 1999 accounting primarily for the differences observed
between years. While reconstituted prey biomass per scat was similar between years, scats
from 1998 represented less energy per gram than those from 1999 and 2000. This study highlights the
usefulness of using FA signature analysis to confirm longer-term shifts in dietary intake of fur seals using
milk samples. Polyunsaturated fatty acids (PUFAs) were significantly more prevalent in the 1999
milk samples, which were also lower in overall lipid content (43% vs 53%). G. nicholsi, a particularly
oily fish, occurred in higher proportions in the diet in 2000, perhaps explaining the higher incidence of
monounsaturated fatty acids (MUFAs) in this year and the generally higher lipid levels present in milk
samples. The inter-annual variation in the diet of Antarctic fur seals confirmed by these 2 techniques
lends support to the hypothesis that previously identified variations in oceanographic conditions
surrounding Îles Kerguelen in 1998, 1999 and 2000 affect the availability of fur seal prey resources.

Item Type: Article
Keywords: Myctophid · Fatty acid · Kerguelen · Lipids · Fish · Squid ·Arctocephalus gazella
Journal or Publication Title: Marine Ecology Progress Series
Page Range: pp. 281-297
ISSN: Print 0171-8630 Online 1616-1599
Identification Number - DOI: 10.3354/meps245281
Date Deposited: 22 Sep 2009 04:33
Last Modified: 18 Nov 2014 04:06
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