Arctic | Mammals DOCTORATE ORAL PRESENTATION Variability in the presence of subarctic whales in relation to environmental conditions in the Bering Strait
Presenter: Erica Escajeda , escajeda@uw.edu, University of Washington Kate Stafford , kate.stafford@oregonstate.edu, Oregon State University Rebecca Woodgate , woodgate@apl.washington.edu, University of Washington Kristin Laidre , klaidre@uw.edu, University of Washington
Subarctic baleen whales, including humpback ( Megaptera novaeangliae ), fin ( Balaenoptera physalus ), and gray whales ( Eschrichtius robustus ) are summer visitors to the Pacific Arctic, migrating through the Bering Strait and into the southern Chukchi Sea to feed on seasonally-abundant prey. The acoustic occurrence of all three species in the Bering Strait varies from year-to-year, possibly reflecting fluctuating environmental conditions. Using acoustic recordings collected over 2009–2018 from a moored hydrophone just north of the strait, we identified whale calls during the open-water season (May–early December), examined the timing of migration, and investigated potential environmental drivers of whale presence. We hypothesized that as sea ice melts earlier and forms later in the Bering and Chukchi seas, all three species would arrive earlier to the region and leave later. We also hypothesized that concurrent conditions at the study site (including temperature, salinity, wind, and water speed) and atmospheric indices (AO, NPGO, PDO, and ENSO) affect the probability of a calling whale being present. We found interannual variability in the acoustic presence of humpback and fin whales with the highest proportion of hours with humpback whale calls in 2009, 2017, and 2018 (17% for each year compared to 4‒13% for other years), and the highest proportion of hours with fin whale calls in 2015, 2017, and 2018 (18‒20% of total recordings each year compared to 4‒14% other years). Gray whale detections gradually increased from 3‒7% of recordings for 2009‒2013, to a maximum of 27% of recordings in 2018. We did not observe a trend among the arrival dates; however, fin whales had a significant trend for later departure dates (~3 days/year, p = 0.02). Significant correlations between sea-surface (R2 ≥ 0.55, p < 0.03) and near-bottom temperatures in the fall (R2 ≥ 0.62, p < 0.01) and departure dates for fin and humpback whales suggest that warmer water temperatures are allowing both species to stay in the region for longer. Beta-binomial models for each species identified a combination of concurrent and time-lagged environmental variables, as well as ocean basin-scale atmospheric indices as significant predictors for the presence of each species during the open-water season, suggesting that conditions earlier in the year as well as elsewhere in their migration range affect the acoustic presence of subarctic whales in the Pacific Arctic.
Alaska Marine Science Symposium 2023 77
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