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I. Background I. BACKGROUND <strong>Polar</strong> bears occur in 19 subpopulations throughout the seasonally and permanently ice-covered marine waters of the northern hemisphere (Arctic and Subarctic), in Canada, Denmark (Greenland), Norway, Russia, and the United States (Fig. 1). The United States contains portions of two subpopulations: the Chukchi Sea and the Southern Beaufort Sea. These 2 subpopulations have also been identified as “stocks” under the MMPA. <strong>Polar</strong> bear subpopulations have been further classified as occurring in one of four ecoregions (Fig. 2, Amstrup et al. 2008) based on the spatial and temporal dynamics of sea ice in the subpopulation’s range. Subpopulations classified as occurring in the Seasonal Ice Ecoregion share the characteristic that the sea ice in their range fully melts in the summer, during which time bears are forced on shore for extended periods of time until the sea ice reforms. Subpopulations occurring in the Archipelago Ecoregion are characterized as having heavy annual and multi-year sea ice that fills the channels between the Canadian Arctic Islands. <strong>Bear</strong>s in this ecoregion remain on the sea ice throughout the year. The <strong>Polar</strong> Basin Divergent Ecoregion, which includes the two United States subpopulations, is characterized by the formation of annual sea ice that is swept away from the shore as sea ice melts during the summer. The <strong>Polar</strong> Basin Convergent Ecoregion is characterized by annual sea ice that converges towards shoreline, allowing bears access to nearshore ice year-round. Although information is limited, the global genetic structure of polar bears appears to reflect the four ecoregions (Paetkau et al. 1999, Peacock et al. 2015). The most recent circumpolar population estimate by the IUCN Red List Assessment was 26,000 (95% Confidence Interval of 22,000 to 31,000) polar bears (Wiig et al. 2015). Figure 1. Map of the polar bear subpopulations (source: <strong>Polar</strong> <strong>Bear</strong> Specialist Group). The subpopulations include: Southern Beaufort Sea (SB), Chukchi Sea, Laptev Sea, Kara Sea, Barents Sea, East Greenland, Northern Beaufort (NB), Kane Basin (KB), Norwegian Bay (NW), Lancaster Sound (LS), Gulf of Boothia (GB), M’Clintock Channel (MC), Viscount Melville Sound (VM), Baffin Bay, Davis Strait, Foxe Basin, Western Hudson Bay (WH), Southern Hudson Bay and the Arctic Basin (AB). <strong>Polar</strong> <strong>Bear</strong> Conservation Management Plan 9