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Studies of the impacts of climate change on Arctic marine ecosystems have largely centered on endemic species and ecosystems, and the people who rely on them. Fewer studies have focused on the northward expansion of upper trophic level (UTL) subarctic species. We provide an overview of changes in the temporal and spatial distributions of subarctic fish, birds, and cetaceans, with a focus on the Pacific Arctic Region. Increasing water temperatures throughout the Arctic have increased “thermal habitat” for subarctic fish species, resulting in northward shifts of species including walleye pollock and pink salmon. Ecosystem changes are altering the community composition and species richness of seabirds in the Arctic, as water temperatures change the available prey field, which dictates the presence of planktivorous versus piscivorous seabird species. Finally, subarctic whales, among them killer and humpback whales, are arriving earlier, staying later, and moving consistently farther north, as evidenced by aerial survey and acoustic detections. Increasing ice-free habitat and changes in water mass distributions in the Arctic are altering the underlying prey structure, drawing UTL species northward by increasing their spatial and temporal habitat. A large-scale shuffling of subarctic and Arctic communities is reorganizing high-latitude marine ecosystems. [ABSTRACT FROM AUTHOR]

Information on factors contributing to the morbidity and mortality of the Bering–Chukchi–Beaufort seas stock of bowhead whales (Balaena mysticetus) is fundamental to its successful management and recovery. The Alaska Arctic coastline is remote and expansive, making monitoring for and gross examination of carcasses difficult. However, sighting data and imagery collected during aerial surveys in the eastern Chukchi (EC) and western Beaufort (WB) seas from 2009 through 2019 provide information on bowhead whale mortality. We present bowhead whale carcass data from the 2019 aerial surveys that add to the long series of consistent information on floating and beach-cast bowhead whale carcasses. The 2019 carcass data suggest an increased occurrence of probable killer whale (Orcinus orca) predation on bowhead whales in the WB. Eleven bowhead whale carcasses were photo-documented from July to October 2019 in the EC and WB study areas. Of the 11 carcasses documented, 7 had injuries consistent with probable killer whale predation—2 in the EC and 5 in the WB. Probable cause of death could not be assigned to four carcasses. No carcasses were associated with aboriginal subsistence hunting. Despite similar annual survey effort from 2009 to 2019, several compelling deviations in carcass numbers and locations were observed in 2019. Compared to 2009–2018, 2019 had the highest yearly number of documented carcasses and the most categorized as probable killer whale predation. Carcass locations exhibited a striking shift from the EC to the WB. Lastly, more carcasses were categorized as probable killer whale predation in the WB during 2019 than in 2009–2018 combined. [ABSTRACT FROM AUTHOR]

Examining Eastern North Pacific gray whale (Eschrichtius robustus) carcasses and tracking mortality and morbidity are essential for assessing the health of this stock. In the eastern Chukchi Sea, the expansive coastline relative to few coastal communities makes monitoring for and physical examination of gray whale carcasses difficult. The Aerial Surveys of Arctic Marine Mammals (ASAMM) project offers an unparalleled dataset of gray whale carcasses, documented and photographed from July to October 2009–2019, providing a unique opportunity to investigate imaged gray whale carcasses for possible cause of death. Surveys covered expanses of gray whale and killer whale (Orcinus orca) summer and autumn habitat. ASAMM documented a total of 59 gray whale carcasses, distributed across the eastern Chukchi Sea (67.5° N–72.0° N, 155.5° W–169.0° W). Carcass sighting rates ([CPUE] carcasses per 1000-km of effort) varied by month and year. The highest numbers of carcasses were observed in 2012 (13) and 2019 (8). August had the highest number of gray whale carcass sightings (22) and the highest carcass sighting rate (0.231 CPUE). Images were obtained for 56 gray whale carcasses. The majority (41) of imaged gray whale carcasses had injuries consistent with probable killer whale predation, and were photo-documented every year except 2010 (when no carcasses were seen) and 2011. Eight carcasses were suspect killer whale predation, and cause of death could not be determined for seven carcasses. These results will be valuable for evaluating mortality, concurrent with rapid oceanographic changes, and increases in anthropogenic activities. [ABSTRACT FROM AUTHOR]

Imagery and sighting data on bowhead whale (Balaena mysticetus) carcasses documented from 2009 to 2018 during aerial surveys in the eastern Chukchi and western Beaufort seas have provided evidence for killer whale (Orcinus orca) predation on bowhead whales of the Bering–Chukchi–Beaufort Seas stock. The Aerial Surveys of Arctic Marine Mammals (ASAMM) project provides information on distribution, behavior, and relative density of marine mammals. ASAMM surveys large areas of bowhead whale and killer whale summer and autumn habitat and offers consistent information on bowhead whale carcasses. Thirty-three bowhead whale carcasses were documented in July–October, from 2009 to 2018. Carcasses were distributed across the eastern Chukchi and western Beaufort seas from 141.6° W to 168.1° W and 68.9° N to 72.0° N. Carcass sighting rates (carcasses/1000 km) varied by month, year, and region. Statistical results suggest an alternating series of high and low annual carcass sighting rates. Eighteen bowhead whale carcasses having injuries consistent with probable killer whale predation were photo-documented: four each in 2016 and 2018, three each in 2013 and 2015, two in 2012, and one each in 2010 and 2017. Four carcasses, two in 2015 and one each in 2013 and 2018, were likely whales struck and lost during aboriginal subsistence hunting. Cause of death could not be determined for 11 carcasses. This study is the first systematic inquiry into non-harvest related mortality of bowhead whales in the U.S. Pacific Arctic and provides multi-year evidence for killer whale predation on bowhead whales in this portion of their range. [ABSTRACT FROM AUTHOR]

Collisions between vehicles and wildlife is a global conservation concern, and vessel strikes are a leading cause of serious injury and mortality for baleen whales. Yet vessel strikes have rarely been studied in the Arctic. Vessel traffic is increasing throughout the Arctic as sea ice is declining, leading to increased overlap between vessels and whales. We examined hypothetical vessel strike risk for the Bering-Chukchi-Beaufort (BCB) and Eastern Canada-West Greenland (ECWG) populations of bowhead whales during the open-water shipping season. We used satellite telemetry and aerial survey data to calculate monthly relative density of both populations, and satellite vessel tracking data to calculate monthly vessel density and speed. We estimated vessel strike risk by multiplying whale density by vessel density corrected by vessel speed. For the BCB population, the highest relative risk was near Utqiaġvik and Prudhoe Bay, Alaska, USA, and near Tuktoyaktuk, Northwest Territories, Canada. For the ECWG population, the highest risk was in the Gulf of Boothia, Cumberland Sound, and near Isabella Bay, Nunavut, Canada. Strike risk was highest in August and September, corresponding with monthly trends in vessel traffic. This study provides important information for focussed monitoring and to minimize/mitigate the threat of vessel strikes to bowhead whales. Although vessel strike risk is presently lower for these populations than for other temperate large cetacean populations, bowhead whale behaviour and projected increases in traffic elevates their risk in the Arctic. Measures to mitigate vessel strike risk to bowhead whales will likely benefit other Arctic marine mammals like beluga and narwhal. [ABSTRACT FROM AUTHOR]

Bearded seals are pan-Arctic ice-obligate phocids; for the threatened Beringia population, the majority of the population feeds in the summer in the Chukchi Sea, then migrates south to overwinter in the northern Bering Sea. Contemporary information on the impact of rapidly changing climatic conditions on bearded seal distribution is essential for effective management. To monitor for marine mammals, passive acoustic recorders were deployed throughout the eastern Chukchi and northern Bering seas (64° N to 72° N), sampling at a rate of 16 kHz on a duty cycle of either 80 or 85 min every 5 h. Data from year-long deployments at nine sites over four years (2012–2016) were manually analyzed, totaling 13,275 days (∼75,000 h). Bearded seal calling activity was present at every site in every year. Calling activity increased from September through February and reached sustained and saturated levels from March through June, at which point calling ceased abruptly regardless of ice cover. The timing of calling and its abrupt cessation correspond with the known breeding season of bearded seals. However, the timing of the cessation of calling occurred earlier each year, corresponding with an earlier sea ice retreat. The sustained calling detected overwinter at all locations suggests that this is more than just a few animals that are remaining in the Chukchi Sea. Preceding this main pulse was a smaller peak in calling that progressed southward, corresponding with the fall migration of bearded seals to the Bering Sea. These results increase our knowledge on the year-round spatio-temporal distribution and migration patterns of this pagophilic species, and the relationship between calling activity and sea ice concentration. [ABSTRACT FROM AUTHOR]