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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations
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hunting ceased in 1972 with the passage of the MMPA and ceased in 1990 in Russia. Presently, walrus hunting in Alaska is restricted to subsistence use by Alaska Natives. Harvest mortality during 20002018 for both the United States and Russian Federation averaged 3,207 SE = 194 walruses per year. This mortality estimate includes corrections for under-reported harvest and struck and lost animals. Harvests have been declining by about 3 percent per year since 2000 and were exceptionally low in the United States in 20122014.
Resource managers in Russia have concluded that the population has declined and have reduced harvest quotas in recent years accordingly Kochnev 2004; Kochnev 2005; Kochnev 2010; pers. comm.; Litovka 2015, pers.
comm. based in part on the lower abundance estimate generated from the 2006 survey. Total harvest quotas in Russia were further decreased in 2020 to 1,088 walruses Ministry of Agriculture of the Russian Federation Order of March 23, 2020. Intra-specific trauma at coastal haulouts is also a known source of injury and mortality Garlich-Miller et al. 2011. The risk of stampederelated injuries increases with the number of animals hauled out and with the duration spent on coastal haulouts, with calves and young being the most vulnerable to suffer injuries and/or mortality USFWS 2017. However, management and protection programs in both the United States and the Russian Federation have been somewhat successful in reducing disturbances and large mortality events at coastal haulouts USFWS 2015.
Climate Change Global climate change will impact the future of both Pacific walrus and polar bear populations. As atmospheric greenhouse gas concentrations increase so will global temperatures Pierrehumbert 2011; IPCC 2014 with substantial implications for the Arctic environment and its inhabitants Bellard et al. 2012, Scheffers et al. 2016, Harwood et al. 2001, Nunez et al. 2019.
The Arctic has warmed at twice the global rate IPCC 2014, and long-term data sets show that substantial reductions in both the extent and thickness of Arctic sea-ice cover have occurred over the past 40 years Meier et al. 2014, Frey et al. 2015. Stroeve et al. 2012 estimated that, since 1979, the minimum area of fall Arctic sea-ice declined by over 12 percent per decade through 2010. Record low minimum areas of fall Arctic sea-ice extent were recorded in 2002, 2005, 2007, and 2012.
Further, observations of sea-ice in the Beaufort Sea have shown a trend since
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2004 of sea-ice break-up earlier in the year, re-formation of sea-ice later in the year, and a greater proportion of firstyear ice in the ice cover Galley et al.
2016. The overall trend of decline of Arctic sea-ice is expected to continue for the foreseeable future Stroeve et al.
2007; Amstrup et al. 2008; Hunter et al.
2010; Overland and Wang 2013; 73 FR
28212, May 15, 2008; IPCC 2014.
Decline in Arctic sea ice affects Arctic species through habitat loss and altered trophic interactions. These factors may contribute to population distribution changes, population mixing, and pathogen transmission Post et al. 2013, which further impact population health.
For polar bears, sea-ice habitat loss due to climate change has been identified as the primary cause of conservation concern e.g., Stirling and Derocher 2012, Atwood et al. 2016b, USFWS 2016. A 42 percent loss of optimal summer polar bear habitat throughout the Arctic is projected for the decade of 20452054 Durner et al.
2009. A recent global assessment of the vulnerability of the 19 polar bear stocks to future climate warming ranked the SBS as one of the three most vulnerable stocks Hamilton and Derocher 2019.
The study, which examined factors such as the size of the stock, continental shelf area, ice conditions, and prey diversity, attributed the high vulnerability of the SBS stock primarily to deterioration of ice conditions. The SBS polar bear stock occurs within the Polar Basin Divergent Ecoregion PBDE, which is characterized by extensive sea-ice formation during the winters and the sea ice melting and pulling away from the coast during the summers Amstrup et al. 2008. Projections show that polar bear stocks within the PBDE may be extirpated within the next 4575 years at current rates of sea-ice declines Amstrup et al. 2007, Amstrup et al.
2008. Atwood et al. 2016 also predicted that polar bear stocks within the PBDE will be more likely to greatly decrease in abundance and distribution as early as the 20202030 decade primarily as a result of sea-ice habitat loss.
Sea-ice habitat loss affects the distribution and habitat use patterns of the SBS polar bear stock. When sea ice melts during the summer, polar bears in the PBDE may either stay on land throughout the summer or move with the sea ice as it recedes northward Durner et al. 2009. The SBS stock, and to a lesser extent the Chukchi Sea stock, are increasingly utilizing marginal habitat i.e., land and ice over less productive waters Ware et al. 2017.
Polar bear use of Beaufort Sea coastal areas has increased during the fall open-

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water period June through October.
Specifically, the percentage of radiocollared adult females from the SBS
stock utilizing terrestrial habitats has tripled over 15 years, and SBS polar bears arrive onshore earlier, stay longer, and leave to the sea ice later Atwood et al. 2016b. This change in polar bear distribution and habitat use has been correlated with diminished sea ice and the increased distance of the pack ice from the coast during the open-water period i.e., the less sea ice and the farther from shore the leading edge of the pack ice is, the more bears are observed onshore Schliebe et al. 2006;
Atwood et al. 2016b.
The current trend for sea-ice in the SBS region will result in increased distances between the ice edge and land, likely resulting in more bears coming ashore during the open-water period Schliebe et al. 2008. More polar bears on land for a longer period of time may increase both the frequency and the magnitude of polar bear exposure to human activities, including an increase in humanbear interactions Towns et al. 2009, Schliebe et al. 2008, Atwood et al. 2016b. Polar bears spending more time in terrestrial habitats also increases their risk of exposure to novel pathogens that are expanding north as a result of a warmer Arctic Atwood et al.
2016b, 2017. Heightened immune system activity and more infections indicated by elevated number of white blood cells have been reported for the SBS polar bears that summer on land when compared to those on sea ice Atwood et al. 2017; Whiteman et al.
2019. The elevation in immune system activity represents additional energetic costs that could ultimately impact stock and individual fitness Atwood et al.
2017; Whiteman et al. 2019. Prevalence of parasites such as the nematode Trichinella nativa in many Arctic species, including polar bears, pre-dates the recent global warming. However, parasite prevalence could increase as a result of changes in diet e.g., increased reliance on conspecific scavenging and feeding habits e.g., increased consumption of seal muscle associated with climate-induced reduction of hunting opportunities for polar bears Penk et al. 2020, Wilson et al. 2017.
The continued decline in sea-ice is also projected to reduce connectivity among polar bear stocks and potentially lead to the impoverishment of genetic diversity that is key to maintaining viable, resilient wildlife populations Derocher et al. 2004, Cherry et al. 2013, Kutchera et al. 2016. The circumpolar polar bear population has been divided into six genetic clusters: The Western Polar Basin which includes the SBS

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