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During periods of year-round ice coverage, observations of marine mammals in the Central Arctic Ocean ecoregion have been limited to very low numbers of ringed seals and polar bears. Recent retreats of the sea ice have been accompanied by increased observations of several ice-dependent species including polar bears, narwhals (Monodon monoceros), ringed seals, and hooded seals (Cystophora cristata). Very few dedicated abundance surveys of marine mammals have been conducted in this area and precise trend information therefore does not exist.
A 2015 marine mammal survey north of Svalbard showed that most polar bears in this area are now foraging on the southern border of the Eurasian Basin. Few seals were observed, but subsequent assessments of the bears’ nutritional status suggest that a suitable prey base has been available over the last years. A rather large concentration of narwhals was also documented in this area for the first time.
Gateways and shelf areas adjacent to the ecoregion are documented feeding areas for all eleven ice-dependent Arctic marine mammal species (walruses [Odobenus rosmarus], bearded seals [Erignathus barbatus], ringed seals, harp seals [Pagophilus groenlandicus], hooded seals, ribbon seals [Histriophoca fasciata], spotted seals [Phoca largha], beluga whales [Delphinapterus leucas], narwhals, bowhead whales [Balaena mysticetus] and polar bears). In addition, other species like grey whales (Eschrichtius robustus), humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus), blue whales (Balaenoptera musculus), minke whales (Balaenoptera acutorostrata), and killer whales (Orcinus orca) are increasingly observed in the border areas of the ecoregion during summer. Of these, grey whales have been considered endemic to the Pacific since the 18th century when the Atlantic grey whale population went extinct. Over the past decade, however, at least three grey whales are known to have entered the Atlantic Ocean, most likely via the shelf and slope areas bordering the ecoregion. This illustrates the increased potential for long distance species exchange, population mixing, and pathogen transfer between Arctic marine mammal communities due to reduced ice cover in the ecoregion.
