Affiliation:
1. Department of Wildlife Management North Slope Borough Alaska
2. Givens Statistical Solutions, Santa Cruz, California; and Department of Statistics University of California at Santa Cruz California
3. College of Fisheries and Ocean Sciences, University of Alaska Fairbanks Alaska
4. Alaska Sea Grant, Marine Advisory Program University of Alaska Fairbanks Alaska
5. Department of Veterinary Integrative Biosciences College of Veterinary Medicine and Biomedical Sciences, Texas A&M University Texas
Abstract
AbstractData from Bering‐Chukchi‐Beaufort Seas bowhead whales (Balaena mysticetus), harvested during 1973–2021 by aboriginal subsistence hunters, were used to estimate reproductive parameters: length at sexual maturity (LSM), age at sexual maturity (ASM), pregnancy rate (PR), and calving interval. Sexual maturity (N = 187 females) was determined from the presence/absence of corpora in the ovaries, or a fetus. Using sampling bias‐corrected logistic regression, LSM was estimated at 13.5 m, 95% CI [13.0, 13.8]. There was a downward trend in LSM over time, statistically significant with one method but marginal with another. A growth model translated this estimate to an ASM estimate of 23.5 years, 95% CI [20.4, 26.7]. Pregnancy rate was determined from mature females (N = 125), and from a subset limited to certain autumn‐caught whales (n = 37) to reduce bias. The PR was estimated at 0.46 globally, 95% CI [0.36, 0.55] and 0.38 for the autumn sample, 95% CI [0.20, 0.51]. Both estimated PRs are consistent with a 3‐year calving interval, because the larger estimate includes two cohorts of pregnant whales harvested in spring, and bowhead whale gestation is longer than 12 months. These analyses represent the most conclusive empirical estimates of ASM, LSM, and PR for this bowhead whale stock from the largest available data sets to date.
Funder
National Oceanic and Atmospheric Administration
U.S. Department of the Interior
U.S. Fish and Wildlife Service
Subject
Aquatic Science,Ecology, Evolution, Behavior and Systematics
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