Arctic | Mammals
Oceanographic influences on spotted seal foraging in the Pacific Arctic Presenter: Justin Olnes , justin.olnes@alaska.gov, Alaska Department of Fish and Game Justin Crawford , justin.crawford@alaska.gov, Alaska Department of Fish and Game - Arctic Marine Mammal Program Stephen Okkonen , srokkonen@alaska.edu, University of Alaska Fairbanks John Citta , john.citta@north-slope.org, North Slope Borough Lori Quakenbush , lori.quakenbush@alaska.gov, Alaska Department of Fish and Game - Arctic Marine Mammal Program Andrew Von Duyke , Andrew.VonDuyke@north-slope.org, North Slope Borough Department of Wildlife Management Wieslaw Maslowski , maslowsk@nps.edu, Naval Postgraduate School Robert Osinski , rosinki@nps.edu, Institute of Oceanology, Polish Academy of Sciences Matthew Druckenmiller , druckenmiller@colorado.edu, National Snow and Ice Data Center, University of Colorado Boulder Spotted seals ( Phoca largha ) are one of four species of sea ice-associated seals that occur in the Bering, Chukchi, and Beaufort (BCB) seas of the Pacific Arctic. Between 2016 and 2020, 23 spotted seals were equipped with Satellite Relay Data Loggers with miniaturized Conductivity, Temperature, and Depth sensors capable of collecting temperature and salinity profiles as the seals dove through the water column. These instruments (referred to as CTD-SRDLs) provided animal movement and oceanographic data that we used to explore relationships between spotted seal foraging behavior, distinct water masses, hydrographic fronts, and other stratified features that may contain or aggregate prey. We first mapped the oceanographic characteristics where seals traveled and dove using data from the CTD-SRDLs, and then modeled seal behavioral state as a function of sea ice and oceanographic conditions extracted from the interpolated oceanographic space. Because CTD-SRDL data can only provide information along a seal’s track, we also used modeled oceanographic variables from the Regional Arctic System Model (RASM) to examine habitat characteristics surrounding each seal track. Spotted seals mostly foraged closer to land (< 50 km) in water with a relatively fresh signature indicative of coastal waters influenced by river discharge. Seals also traveled farther offshore to forage where the water column was more stratified, surface waters were more saline relative to nearshore surface waters, and bottom temperatures were colder. These latter conditions are indicative of waters originating in the western Bering Sea that move northward via currents that are typically offshore. Data from RASM indicates that seals use the hydrographic fronts between the relatively fresh and warm coastal water and relatively saline and cold water originating from the western Bering Sea. Interestingly, sea ice conditions were not strong predictors of spotted seal foraging behavior. Stomach contents data from subsistence-harvested seals suggest seals are targeting saffron cod and rainbow smelt in the nearshore environment, and Pacific herring, Arctic cod, and capelin when foraging farther offshore. This combination of satellite telemetry, oceanographic modeling, and biological sampling is expanding our understanding of spotted seal foraging habitat, prey species, and behavior in the BCB, and how they may be responding to changing sea ice and oceanographic conditions across the region.
Alaska Marine Science Symposium 2023 80
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