| Abstrakt: |
Subarctic baleen whales, including humpback (Megaptera novaeangliae), fin (Balaenoptera physalus), and gray whales (Eschrichtius robustus), migrate through the Bering Strait every summer to feed in the Chukchi Sea. When and where the whales are found in the region likely reflects environmental conditions. Using recordings collected between 2009 and 2018 from a hydrophone ~ 35 km north of the strait, we identified whale calls during the open-water season (May–December), examined migration timing, and investigated potential drivers of whale presence. The acoustic presence of fin and humpback whales varied across the years, while gray whales were consistently detected each year. We compared detection rates for October and November since these months had recordings each year. We observed the highest proportion of recordings with humpback whale calls for October–November in 2009, 2017, and 2018 (66–80% of recordings); the highest proportion of recordings with fin whale calls in 2015, 2017, and 2018 (75–79% of recordings); and the highest proportion of recordings with gray whale calls in 2013 and 2015 (46 and 51% of recordings, respectively). Fin and humpback whales departed the Bering Strait ~ 3 and 2 days later per year over the study period (p< 0.04). Both fin and humpback whales delayed their southward migration in years with warmer water temperatures (Pearson r≥ 0.73, p< 0.02). Generalized additive models of location, shape, and scale identified day of the year, water temperatures, and the lagged presence of a thermal front the previous month as drivers of acoustic presence for all three species during the open-water season. |
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