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SC/69B/ASW/05
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Resource ID
22019
Access
Open
Document Number
SC/69B/ASW/05
Full Title
2022-2023 Health Report for the Bering-Chukchi-Beaufort Seas bowhead whales
Author
Raphaela Stimmelmayr, John J. Citta, Kayla Scheimreif, Geof H. Givens, Amelia Brower, Kathleen M. Stafford, Angela R. Szesciorka, Andrew L. Von Duyke, Brian T. Person, Todd L. Sformo, Leandra De Sousa
Authors Summary
The 5th BCB bowhead health report (SC/69b/ASW/05) summarizes general status and health information of bowhead whales during 2022 and 2023. No new information on population size or trend are available; the most recent estimates are both from 2019: 14,025 (CV=0.23) from an ice-based survey and 17,175 whales (CV = 0.24) from an aerial survey. Additional ice-based and aerial surveys are scheduled for 2025. Multiple lines of evidence (aerial surveys, satellite tagging and acoustics) suggest bowhead whales are shifting their winter range northward and expanding their summer ranges. Body condition of landed whales remains mostly stable over time, but may be lower in post-weaning whales in recent years. Length at sexual maturity has declined; compared to 1976-1990, length at sexual maturity is now ~1.5 m shorter. Pregnancy rate during 1973-2021 was 0.38 (95% CI = 0.20-0.51) with a 3-yr calving interval, consistent with prior analyses. Disease conditions other than parasitic kidney worm infection, now endemic, remain rare in bowhead whales. The percentage of landed whales with scars from ship strikes in 2022 (6%) and 2023 (8.7%) exceed the prior baseline percentage (2%); a new trend analysis of scarring data is planned. Stranding data (0 in 2022 and 5 in 2023) indicate that killer whale predation remains the main source of natural mortality (4 out of 5 strandings). In summary, bowhead whales are responding to rapid environmental change in the Arctic but population indices and general health assessment findings reiterate that the general health of whales remains good and the harvest is sustainable. Continued harvest and health monitoring of the BCB bowhead whale population remains critical to aid in our general understanding of the complex pathways and mechanisms by which climate change is influencing bowhead populations.
Publisher
IWC
Publication Year
2024
Abstract
ABSTRACT At the 2016 IWC Scientific Committee meeting, it was agreed that an annual or biannual report on the Bering-Chukchi-Beaufort Seas (BCB) bowhead whale stock would be submitted that summarizes health-related data from multiple disciplines. This summary is intended to provide ancillary but pertinent information for informing management recommendations and tracking the status of the BCB bowhead whale stock. This report is the fifth of the series and summarizes general information on population indices, whale health, and hunter observations of bowhead whales for 2022 and 2023. We provide new information on 12 indices: (1) population size and trends; (2) adult survival rate; (3) acoustic index of relative abundance of migrating whales; (4) distribution and migration; (5) calf production (aerial surveys); (6) pregnancy rates of landed adult females; (7) body condition of landed whales; (8) whale lice burden of landed whales; (9) proportion of landed whales showing evidence of feeding; (10) proportion of landed whales with injuries consistent with line entanglement, killer whale attacks and/or vessel collisions; (11) non-harvest related mortality of bowhead whales; (12) health assessment of landed whales; and (13) hunter observations. These indices suggest that the bowhead population remains robust and that the subsistence harvest is sustainable. We will continue to monitor these indices in the coming years.