Data 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.

We examined the response of bowhead whale (Balaena mysticetus) body condition to summer sea ice conditions and upwelling-favorable winds. We used a long-term dataset collected from whales of the Bering-Chukchi-Beaufort Seas (BCB) stock to estimate various body condition indices (SCI's) for individual whales that were harvested by Alaskan Eskimos. A series of offshore regions frequented by bowhead whales in summer were delineated and used to quantify interannual summertime environmental conditions including: (a) mean open water fraction, (b) duration of melt season, (c) date of continuous freeze-up, and (d) mean upwelling-favorable wind stress. Body condition was analyzed relative to these metrics for both the preceding summer feeding season and the previous three seasons combined. Our analysis indicates a significant increase in the long-term trend in an axillary girth-based body condition index (BCIG) over the study period (1989-2011). The increase in BCIG is likely associated with the trend in overall reduction of sea ice, including increased duration of open water, changes in upwelling potential (wind stress), and possibly higher primary production in the Pacific Arctic marine ecosystem favoring water-column invertebrates. We found strong significant positive correlations between BCIG and late summer open water fraction in the Beaufort Sea and smaller nearshore areas off the Mackenzie Delta and west of Banks Island. Additionally, BCIG was positively and significantly correlated with duration of melt season, later date of freeze-up in the Beaufort Sea, and upwelling-favorable winds on the Mackenzie shelf and west of Banks Island. A strong seasonal difference in BCI's was noted for subadult bowheads, presumably associated with summer feeding; however, yearlings were found to drop in BCI over at least the first summer after weaning. Our results indicate an overall increase in bowhead whale body condition and a positive correlation with summer sea ice loss over the last 2.5 decades in the Pacific Arctic. We speculate that sea ice loss has positive effects on secondary trophic production within the BCB bowhead's summer feeding region. While not part of this study, the abundance of BCB bowheads increased markedly over the same period. (C) 2015 Elsevier Ltd. All rights reserved.

In 2008, 50 bowhead whales (Balaena mysticetus) were struck during the Alaskan subsistence hunt resulting in 38 animals landed. Total landed for 2008 was similar to the average over the past 10 years (1998-2007: mean = 40.4; SD = 7.1). The efficiency (# landed / # struck) of the hunt was 76%, which is higher than the average during 1998-2007 (mean = 65%, SD = 8%). Spring hunts are more difficult than autumn ones because of challenging sea ice, weather conditions, and struck whales diving under the shore-fast or into the broken pack ice. The efficiency of the spring hunt was 60% compared to an autumn efficiency of 92%. Of the landed whales 18 were males, 19 were females and sex was not determined for one animal. Of the 19 females of known length, 6 were presumably mature (>13.4m in length). Only one of the mature females was examined closely and she had an active follicle. Hunters reported that one mature female was pregnant with a fetus approximately ~3m in length. Most of the mature females were not closely examined as biologists were either not stationed in the villages or the whales were butchered in the water. One landed whale was a (male) calf, 7.2 m in length, which was swimming alone. Hunters thought this animal was an independent subadult.

In 2015, 48 bowhead whales (Balaena mysticetus) were struck during the Alaskan subsistence hunt resulting in 38 animals landed. Two other whales were found dead. Skin with blubber was removed from both for human consumption resulting in a total of 50 bowheads used in 2015. The total number of whales landed and struck in 2015 was a bit lower than the average for the previous 10 years (2005-2014: mean of landed = 41.8; SD =8.5; mean struck = 55.9; SD =11.9; respectively). The efficiency (# landed / # struck) of the hunt (79%) was a bit higher than the average over the past 10 years (mean of efficiency = 75.3%; SD =0.1%). Total mortality of the hunt for 2015 was estimated at 44 animals after the fate of the struck and lost whales was considered. Spring hunts are logistically more difficult than autumn hunts because of challenging environmental conditions, difficulty in accessing open water, and sea ice dynamics. Typically, hunting efficiency during spring is lower than autumn. In 2015, the efficiency of the spring hunt (67%) was considerably lower than the autumn hunt (92%). This was largely due to mechanical/technical difficulties and the presence of ice during spring. At least one of the struck whales was lost under the ice, two sank and the harpoon came out when being pulled to the surface, and at least four were lost due to equipment failures/technical difficulties. Of the harvested whales, 19 were females and 19 males. The two whales found dead included a male (15B22) and female (2015-FD). Based on total length, 12 of the 19 females were presumed mature (>13.4 m in length). Ten of the mature females were examined. Of those, two had recently given birth, 3 were pregnant with term fetuses (found during the spring hunt), and 2 were pregnant with small fetuses (found during the autumn hunt) suggesting a high pregnancy rate in 2015.