Janet T. Clarke

Increased sightings of subArctic cetaceans in the eastern Chukchi Sea, 2008–2016: population recovery, response to climate change, or increased survey effort?

AbstractCetacean occurrence in the Chukchi Sea is seasonal and primarily driven by annual sea ice retreat and prey occurrence in spring through fall. Humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus), and minke whales (Balaenoptera acutorostrata), although often found in polar waters elsewhere, are not common in the eastern Chukchi Sea, and here are referred to as “subArctic” species. Increasing numbers of these subArctic cetacean species were documented during aerial surveys in the eastern Chukchi Sea (67°–72°N, 157°–169°W) in July–October 2008–2016. The majority (78%) of these sightings occurred on the continental shelf in the south-central Chukchi Sea (67°–69°N, 166°–169°W) in August and September. During similar aerial surveys in 1982–1991, there was a complete lack of sightings of subArctic species. The disparity in sightings between the two time periods could be due to increased marine mammal survey effort in recent years during the months when subArctic cetacean species would be expected to occur, population recoveries from commercial whaling, climate change, or, most likely, a combination of all three.

Presence and behavior of bowhead whales (Balaena mysticetus) in the Alaskan Beaufort Sea in July 2011

The Western Arctic bowhead whale (Balaena mysticetus) is highly adapted to sea ice and annually migrates through the Bering, Chukchi, and Beaufort seas. While the overall distribution and seasonal movements of bowhead whales are mostly understood, information about their distribution in the Alaskan Beaufort Sea in early to mid-summer has not been well documented. In July 2011, we conducted an exploratory flight in the Alaskan Beaufort Sea, north of Camden Bay (71°N 144°W), near the location of a single satellite-tagged bowhead whale. Eighteen bowhead whales were observed, and behavior consistent with feeding was documented. To our knowledge, this is the first documentation of behavior consistent with feeding north of Camden Bay in mid-July. Few studies have focused on bowhead whale distribution in the Alaskan Beaufort Sea in early to mid-summer, and no long-term, region-wide surveys have been conducted during summer. Bowhead whales are already exposed to anthropogenic disturbance in the Canadian Beaufort Sea in summer, the Alaskan Beaufort Sea in fall, and the Chukchi and Bering seas from fall through spring. The presence of bowhead whale aggregations in the Alaskan Beaufort Sea in summer should be considered when assessing the cumulative effects of human-related activities.