MEPS 615:205-220 (2019)  -  DOI: https://doi.org/10.3354/meps12917

ABSTRACT: Interspecific interactions are changing in response to climate change-induced alterations to the physical environment, with consequences for ecosystems. Baseline data on current interactions are needed to improve predictions regarding future changes associated with global warming. Ringed seals Pusa hispida and bearded seals Erignathus barbatus are Arctic species that co-occur across much of this region. In this study, both species were equipped with GPS Argos CTD satellite relay data loggers in Svalbard, Norway, to investigate spatial overlap and species-specific behaviour (2011-2013). Ringed seals spent most of their time near tidal glacial fronts, whereas bearded seals were distributed in shallow, coastal areas; surfacing locations and haul-out events of ringed seals occurred closer to tidal glacier fronts. Thus, spatial overlap was limited between these species, occurring principally in shallow areas near tidal glacier fronts. Ringed seals generally had smaller home ranges, spent less time diving, had shorter dive durations, shorter surface durations between dives, spent a smaller proportion of their dive time in the bottom phase of dives and used different depths for foraging (deeper in autumn and shallower in spring) than bearded seals. Bearded seals dived into Transformed Atlantic Water in the winter, whereas ringed seals occupied Arctic Water masses during this time. Interspecific competition between these species is likely low currently, as they forage in different areas. Future changes in the Arctic may lead to changes in abundance, distribution and diet of these 2 Arctic pinnipeds, with potential consequences for the level of spatial overlap and competition between them.

KEY WORDS: Bearded seals · Erignathus barbatus · Ringed seals · Pusa hispida · Biotic interactions · Competition · Marine mammals · Svalbard