Abstract
We used satellite telemetry to examine bowhead whale movement behavior, residence times, and dive behavior in the Alaskan Beaufort Sea, 2006 – 18. We explored the timing and duration of use of three subregions (western, central, eastern) within the Alaskan Beaufort Sea and applied a two-state switching state-space model to infer bowhead whale behavior state as either transiting or lingering. Transiting whales made direct movements whereas lingering whales changed direction frequently and were presumably feeding. In spring, whales migrated across the Alaskan Beaufort Sea in 7.17 ± 0.41 days, primarily off the continental shelf over deep water. During the autumn migration, whales spent over twice as much time crossing the Alaskan Beaufort Sea than in spring, averaging 18.66 ± 2.30 days, spending 10.05 ± 1.22 days in the western subregion near Point Barrow. Most whales remained on the shelf during the autumn migration and frequently dove to the seafloor, where they spent 45% of their time regardless of behavioral state. Consistent dive behavior in autumn suggests that the whales were looking for food while migrating, and the identification of lingering locations likely reflects feeding. The lack of lingering locations in the eastern and central subregions suggests that prey densities are rarely sufficient to warrant whales pausing their migration for multiple days, unlike in the western subregion near Point Barrow, where bowhead whales regularly lingered for long periods of time.
Highlights
Bowhead whales (Balaena mysticetus) of the BeringChukchi-Beaufort (BCB) stock, known as the Western Arctic stock, make seasonal migrations between wintering grounds in the Bering Sea and primary summer feeding grounds in the Canadian Beaufort Sea (Moore and Reeves, 1993; Citta et al, 2012, 2015; Harwood et al, 2017)
Of the 89 tagged whales, 48 whales had enough data for our sSSM, from which 3178 location estimates were generated in the Alaskan Beaufort Sea
Whales spent an average of ~4 days in each of the eastern and central subregions, but an average of ~10 days in the western subregion (Table 1)
Summary
Bowhead whales (Balaena mysticetus) of the BeringChukchi-Beaufort (BCB) stock, known as the Western Arctic stock, make seasonal migrations between wintering grounds in the Bering Sea and primary summer feeding grounds in the Canadian Beaufort Sea (Moore and Reeves, 1993; Citta et al, 2012, 2015; Harwood et al, 2017). Of primary concern to Native whalers is that these activities may deflect bowhead whales away from important feeding areas and farther offshore where they cannot be harvested (Natural Resource Council, 2003). A recent study, suggested that bowhead whales remain in areas of seismic operations and other activities if they are feeding, but alter their surfacing and diving behavior in response to disturbance (Robertson et al, 2016). To mitigate the impact of oil and gas activities on subsistence resources, significant effort over the last five decades has been made to better understand bowhead whale movements and feeding behavior in the Alaskan Beaufort Sea (Smultea et al, 2012)
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