Bowhead whale calf detections in the western Beaufort sea during the open water season, 2012–2019

• Published in: Arctic Science
• Main Authors: J.T. Clarke, M.C. Ferguson, S.R. Okkonen, A.A. Brower, A.L. Willoughby
• Format: Article in Journal/Newspaper
• Language: English; French
• Published: Canadian Science Publishing 2022
• Subjects: bowhead whale; Bering–Chukchi–Beaufort seas; calf ratio; seasonality; Pacific Arctic; aerial survey; envir; geo; Arctic; Pacific; Amundsen Gulf; Balaena mysticetus; Beaufort Sea; Chukchi
• Online Access: https://doi.org/10.1139/as-2021-0020; https://doaj.org/article/09df679dbe9c49e5ab4556bc4c4cfff0

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.