Abstract
Successful reproduction is essential to a species existence. Here we summarize Bering–Chukchi–Beaufort (BCB) bowhead whale (Balaena mysticetus Linnaeus, 1758) calf distribution, ratio of calf to adult sightings, and encounter rate from data collected during line–transect aerial surveys conducted from July to October 2012–2019 in the western Beaufort Sea (140°W–157°W). During 223,000 on effort km, a total of 274 calves were seen: 100 in summer (July–August) and 174 in fall (September–October), compared with nearly 3,200 non-calves. Calves were widely distributed in the study area in August and September, with distribution in July largely east of 150°W and distribution in October west of 143°W. Calf ratios and encounter rates appear to follow a 3–4 year cycle. Most calves (240/274; 88%) were seen near an adult assumed to be the maternal female, but 9% (26/274) of all calves were observed unaccompanied at the surface and 3% (8/274) were observed with large whales at the surface but not close by. Of the total calves detected, 60% (165/274) were observed after circling was initiated, highlighting the importance of closely investigating all bowhead whale sightings if identification of calves is critical to project goals. Bowhead whale calf data from the eastern Beaufort Sea and Amundsen Gulf in August 2019 are also summarized.
Highlights
A species cannot thrive if it does not successfully reproduce
While most BCB bowhead whales take advantage of productive feeding areas in Canada, some whales may remain in the western Chukchi Sea north of the Chukotka peninsula (Melnikov and Zeh 2007; Moore et al 1995), in the northeastern Chukchi
The Aerial Surveys of Arctic Marine Mammals (ASAMM) project conducted aerial surveys during fall (September-October) in the western Beaufort Sea (WBS; 140°-157°W) every year from 1982 to 2019, providing data on BCB bowhead whale distribution, behavior, and encounter rate
Summary
Increased net primary production (Frey et al 2015; Hill et al 2018) The impacts of these environmental changes on marine life endemic to the Pacific Arctic, including bowhead whales, have been the subject of several recent studies (Ashjian et al 2010; Clarke et al 2016, 2018; Druckenmiller et al 2018; George et al 2015; Moore 2016; Okkonen et al 2018). While most BCB bowhead whales take advantage of productive feeding areas in Canada, some whales may remain in the western Chukchi Sea north of the Chukotka peninsula (Melnikov and Zeh 2007; Moore et al 1995), in the northeastern Chukchi. Obtaining direct evidence of upwelling and prey aggregations is difficult, but investigations of
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