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Marine Ecology Progress Series

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MEPS 409:255-266 (2010)  -  DOI:

Selection of diving strategy by Antarctic fur seals depends on where and when foraging takes place

Simon D. Goldsworthy1,*, Brad Page1, Andrew Welling2, Magaly Chambellant3,5, Corey J. A. Bradshaw1,4

1South Australian Research and Development Institute—Aquatic Sciences Centre, 2 Hamra Avenue, West Beach, South Australia 5024, Australia
2434 Van Morey Road, Margate, Tasmania 7054, Australia
3Centre d’Études Biologiques de Chizé—Centre National de Recherche Scientifique, 79360 Beauvoir-sur-Niort, France
4The Environment Institute and School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
5Present address: Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada

ABSTRACT: We investigated the spatial and temporal distribution of foraging effort by lactating Antarctic fur seals Arctocephalus gazella at Heard Island using satellite telemetry and time-depth recorders. Two principal diving types were identified: ‘deep’ dives averaging 48.6 m, and ‘shallow’ dives averaging 8.6 m. Discriminant function analyses were used to assign dives based on their depth and duration. Generalised linear mixed-effects models of night dives (>80% of all dives) indicated both spatial and temporal effects on the distribution of deep and shallow dives. Deep dives were more common in the deeper shelf waters of the Kerguelen Plateau, and these dives predominantly occurred after sunset and before sunrise. In contrast, shallow dives were more common in slope waters on the southeastern margin of the Kerguelen Plateau in the hours either side of local midnight. We suggest that these 2 distinct diving types reflect the targeting of channichthyid (deep dives) and myctophid (shallow dives) fish, and are indicative of spatial and temporal differences in the availability of these 2 important prey groups. We also identified 3 distinct behavioural dive groups (based on multidimensional scaling of 19 diving and foraging trip parameters) that also differed in their spatial distribution and in their relative importance of deep and shallow dives. The present study provides some of the first evidence that diving strategies are not only influenced by where foraging takes pace, but also when.

KEY WORDS:Diving · Arctocephalus gazelle · Spatial foraging · Southern Ocean · Temporal variability

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Cite this article as: Goldsworthy SD, Page B, Welling A, Chambellant M, Bradshaw CJA (2010) Selection of diving strategy by Antarctic fur seals depends on where and when foraging takes place. Mar Ecol Prog Ser 409:255-266.

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