MEPS 631:209-224 (2019)  -  DOI: https://doi.org/10.3354/meps13145

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