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Marine Ecology Progress Series

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MEPS 631:209-224 (2019)  -  DOI:

Inferring foraging locations and water masses preferred by spotted seals Phoca largha and bearded seals Erignathus barbatus

R. D. Gryba1,7,*, F. K. Wiese2, B. P. Kelly3, A. L. Von Duyke4, R. S. Pickart5, D. A. Stockwell6

1Stantec, Burnaby, BC V5H 0C6, Canada
2Stantec, Anchorage, AK 99503, USA
3Study of Environmental Arctic Change, International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK 99709-3710, USA
4Department of Wildlife Management, North Slope Borough, Utqiaġvik, AK 99723, USA
5Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
6College of Fisheries and Ocean Sciences, Institute of Marine Science, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
7Present address: Statistical Ecology Research Group, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
*Corresponding author:

ABSTRACT: Spotted seals Phoca largha and bearded seals Erignathus barbatus are ice-associated seals that have overlapping range in the Beaufort, Chukchi, and Bering Seas, but have different foraging ecologies. The link between foraging behaviour and specific oceanographic variables is not well understood for these species, nor is the influence of different dive metrics when modelling their foraging behaviour. To explore the value of different dive metrics to estimate foraging behaviour, and the relationships between foraging and water bodies/oceanographic variables, we tagged 3 spotted seals and 2 bearded seals with satellite telemetry tags that recorded movement and oceanographic data. To infer foraging behaviour, we included dive metrics in Bayesian state-space switching models, and found that models that included depth-corrected dive duration were more parsimonious than models that included dive shape. The addition of vertical movements to the model enabled better determination of foraging areas (inferred from area-restricted searches) and provided insights into the probabilities of switching between foraging and transiting behaviours. The collection of oceanographic data in situ at a scale relevant to seals helped identify water masses, and how they were used, and potential oceanographic cues used by seals to identify foraging locations. Fine-scale spatiotemporal clustering analysis revealed spotted and bearded seal foraging ‘hotspots’ in the Chukchi and Bering Seas that overlap with hotspots identified for other marine mammals and marine birds.

KEY WORDS: Ice-associated seals · Foraging · Bayesian state-space models · Satellite telemetry · Oceanographic variables · Spotted seals · Bearded seals · MARES

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Cite this article as: Gryba RD, Wiese FK, Kelly BP, Von Duyke AL, Pickart RS, Stockwell DA (2019) Inferring foraging locations and water masses preferred by spotted seals Phoca largha and bearded seals Erignathus barbatus. Mar Ecol Prog Ser 631:209-224.

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