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The Chukchi Sea environment changes considerably in physical and biological conditions, driven by the expanding volume of warm Pacific summer water. These environmental changes can affect the migration timing of baleen whales in the southern Chukchi Sea. However, few studies have been conducted in this area to determine the migration timing of bowhead whales (Balaena mysticetus), the only baleen whale species endemic to the Arctic region. In this study, we conducted a fixed passive acoustic monitoring of bowhead whales in the southern Chukchi Sea from July 2012 to October 2015 and compared the occurrence patterns of vocalizations to physical and biological environmental factors. Bowhead whale calls were detected in fall/winter and spring during the ice-freezing and retreating periods, respectively. The fall migration timing of bowhead whales through the southern Chukchi Sea was delayed in the years when the timing of sea ice formation was late, and it formed increasingly later in the years 2013, 2014, and 2012, in that sequence. Moreover, the sea surface temperature decreased before freeze-up, which affected the timing of fall migration of bowhead whales. There was no clear relationship between the occurrence of bowhead whale calls and the abundance of prey, especially in spring, suggesting that most bowhead whales use the southern Chukchi Sea as a corridor during their spring northward migrations. However, the occurrence of bowhead whales and high abundance of zooplankton in October–November present the possibility that bowhead whales expand their feeding area in the southern Chukchi Sea.

An ice-based visual survey of the Bering-Chukchi-Beaufort Seas stock of bowhead whales (Balaena mysticetus) was conducted in spring 2019 near Utqiaġvik (formerly Barrow), Alaska. A Horvitz-Thompson-type estimator is used to estimate population abundance from the resulting data, correcting for detection probabilities, whale availability within visual range, and whale passage during periods of missed effort. Analytical methods mirror those used by Givens et al. (2016) for the 2011 survey as much as possible; however, unlike 2011, no simultaneous acoustic monitoring was conducted in 2019, so the availability correction factor had to be estimated from past years. The estimated abundance was 12,505 with 95% confidence interval of (7,994, 19,560) and a CV of 0.228. This estimated abundance is markedly lower than the 2011 estimate of 16,820, but the 2019 confidence interval wholly encompasses the 2011 interval. We do not interpret this finding as evidence of a decline for many reasons including: highly unusual ice conditions, an unusual migration route that was sometimes too distant from observers to detect whales, failure to conduct watch because of closed leads during the early weeks of the migration when numerous whales likely passed, an unusually short perch, and hunters’ heavy use of powered skiffs near the observation perch which likely disturbed the whales during the survey. Furthermore, bowhead health assessment information for 2019 suggests that harvested bowheads did not exhibit obvious reductions in health condition, and aerial surveys in summer 2019 indicated high calf production (Stimmelmayr et al. 2020). Despite the challenges of the 2019 survey, the estimate is adequate for use with the International Whaling Commission’s management procedure and complies with the survey requirements of the Aboriginal Whaling Scheme.

We used satellite telemetry to examine bowhead whale movement behavior, residence times, and dive behavior in the Alaskan Beaufort Sea, 2006 – 18. We explored the timing and duration of use of three subregions (western, central, eastern) within the Alaskan Beaufort Sea and applied a two-state switching state-space model to infer bowhead whale behavior state as either transiting or lingering. Transiting whales made direct movements whereas lingering whales changed direction frequently and were presumably feeding. In spring, whales migrated across the Alaskan Beaufort Sea in 7.17 ± 0.41 days, primarily off the continental shelf over deep water. During the autumn migration, whales spent over twice as much time crossing the Alaskan Beaufort Sea than in spring, averaging 18.66 ± 2.30 days, spending 10.05 ± 1.22 days in the western subregion near Point Barrow. Most whales remained on the shelf during the autumn migration and frequently dove to the seafloor, where they spent 45% of their time regardless of behavioral state. Consistent dive behavior in autumn suggests that the whales were looking for food while migrating, and the identification of lingering locations likely reflects feeding. The lack of lingering locations in the eastern and central subregions suggests that prey densities are rarely sufficient to warrant whales pausing their migration for multiple days, unlike in the western subregion near Point Barrow, where bowhead whales regularly lingered for long periods of time.

This paper examines Neo-Inuit (ca. AD 1250 to present) responses to the decreased temperatures of the Little Ice Age (LIA) climate change episode (ca. AD 1300–1900) in the Foxe Basin region of central Nunavut, Arctic Canada. Cooler temperatures (and increased sea ice) would be expected to have reduced both bowhead whale (Balaena mysticetus) and Atlantic walrus (Odobenus rosmarus rosmarus) habitats, forcing Neo-Inuit to refocus their hunting activities on landfast-ice-dwelling small seals (e.g., Pusa hispida) during winter months. However, an analysis of faunal remains from Foxe Basin's largest-known Neo-Inuit (Thule, historic and modern Inuit) archaeological site, Pingiqqalik (NgHd-1), reveals a long-term subsistence economy based largely on multi-seasonal walrus hunting. Two interrelated factors may explain these results: (1) a system of recurring polynyas provided a degree of ecological stability for local walrus populations, and (2) the development of a distinctive walrus caching regime—a form of which continues among the region's contemporary Inuit—allowed residents to adeptly exploit an ecological niche, thereby ensuring food security. Together, these factors likely insulated northern Foxe Basin Neo-Inuit from the worst effects of the LIA.

Accounts of killer whale (Orcinus orca) predation on marine mammals in the Canadian Arctic are relatively uncommon. Although second-hand reports of killer whale predation events in the Arctic are more common in recent years, these observations are generally poorly documented and the outcome of attacks are often unknown. On 12 August 2016, a floating bowhead whale (Balaena mysticetus) carcass was found off-shore in Cumberland Sound, Nunavut — presumably predated by killer whales that were sighted in the area. Inspection of the carcass revealed injuries consistent with published accounts of killer whale predation on large whales and observations of killer whale predation on bowheads described in Inuit traditional knowledge. The bowhead was male, 6.1 m long in good nutritional condition and estimated between 14 and 16 months old. As a recently weaned yearling, this whale would have been highly vulnerable to killer whale predation. With decreasing summer sea ice making some areas of the Arctic more accessible, the incursion and presence of killer whales in the Arctic is expected to increase. A better understanding of Arctic killer whale predation pressure is needed to predict the potential impact they will have on the eastern Canada–west Greenland bowhead population as well as on other marine mammal prey.

—The bay waters of the Sea of Okhotsk near the Shantar Islands are the most important summer grazing areas for bowhead whales (Balaena mysticetus) of the Okhotsk population. A hydrobiological survey during the period from July 12–28th, 2016, demonstrated that waters around the Shantar archipelago are characterized by high concentrations of humic substance supplied by the peat-laden banks of rivers flowing into the bays. The average chlorophyll concentrations in bottom waters of Uda and Academy bays were 1.1 and 4.3 mg/m3, respectively. Uda and Academy bays are mainly considered heterotrophic and autotrophic basins, respectively. The measured zooplankton biomass in Uda Bay ranged from 9.5 to 2513 mg/m3, averaging 736 mg/m3; the corresponding characteristics in Academy Bay were 0.38 to 3620 mg/m3, averaging 458 mg/m3. In the Shantar water area, copepods of the species Calanus glacialis were the dominant contributor in terms of zooplankton biomass and species abundance. During early summer, nine bowhead whales were sighted south off Feklistov Island and lone whales were recorded in the North Strait and at the mouth of Nikolai Bay. The low density of polar whales in the Shantar water area in early summer may be due to the low zooplankton biomass after spring bloom and the last spawning.

The availability of a food subsidy has the potential to influence the condition, behavior, fitness, and population dynamics of a species. Since the early 2000s, monitoring efforts along the coast of northern Alaska have indicated a higher proportion of polar bears (Ursus maritimus) of the southern Beaufort Sea (SB) subpopulation coming onshore to feed on subsistence-harvested bowhead whale (Balaena mysticetus) carcasses during the fall and early winter seasons. Concurrently, Indigenous communities annually hunt bowhead whale and deposit the unused remains at localized “bone piles,” creating the potential for human-bear interactions. Our objective was to determine the annual number of polar bears feeding at the bone pile near Kaktovik, Alaska. Using a hair snag surrounding the bone pile, we collected hair samples to identify individual bears via microsatellite genotypes during 2011 – 14. We used capture-mark-recapture data in the POPAN open-population model to estimate the number of bears visiting the bone pile. We estimated that as many as 72 (SE = 9) and 76 (SE = 10) male and female polar bears, respectively, used the bone pile located at Kaktovik, Alaska, in 2012, which represents approximately 16% of the SB polar bear subpopulation. It will be important to monitor the number of bears using the bone pile and subsequent human-bear interactions and conflicts along the northern coast of Alaska, if sea ice continues to recede.

The Distributed Biological Observatory (DBO) was established to detect environmental changes in the Pacific Arctic by regular monitoring of biophysical responses in each of 8 DBO regions. Here we examine the occurrence of bowhead and beluga whale vocalizations in the western Beaufort Sea acquired by acoustic instruments deployed from September 2008-July 2014 and September 2016-October 2018 to examine inter-annual variability of these Arctic endemic species in DBO Region 6. Acoustic data were collected on an oceanographic mooring deployed in the Beaufort shelfbreak jet at ~71.4°N, 152.0°W. Spectrograms of acoustic data files were visually examined for the presence or absence of known signals of bowhead and beluga whales. Weekly averages of whale occurrence were compared with outputs of zooplankton, temperature and sea ice from the BIOMAS model to determine if any of these variables influenced whale occurrence. In addition, the dates of acoustic whale passage in the spring and fall were compared to annual sea ice melt-out and freeze-up dates to examine changes in phenology. Neither bowhead nor beluga whale migration times changed significantly in spring, but bowhead whales migrated significantly later in fall from 2008–2018. There were no clear relationships between bowhead whales and the environmental variables, suggesting that the DBO 6 region is a migratory corridor, but not a feeding hotspot, for this species. Surprisingly, beluga whale acoustic presence was related to zooplankton biomass near the mooring, but this is unlikely to be a direct relationship: there are likely interactions of environmental drivers that result in higher occurrence of both modeled zooplankton and belugas in the DBO 6 region. The environmental triggers that drive the migratory phenology of the two Arctic endemic cetacean species likely extend from Bering Sea transport of heat, nutrients and plankton through the Chukchi and into the Beaufort Sea.

The bowhead whale is the only baleen whale endemic to the Arctic and is well adapted to this environment. Bowheads live near the polar ice edge for much of the year and although sea ice dynamics are not the only driver of their annual migratory movements, it likely plays a key role. Given the intrinsic variability of open water and ice, one might expect bowhead migratory plasticity to be high and linked to this proximate environmental factor. Here, through a network of underwater passive acoustic recorders, we document the first known occurrence of bowheads overwintering in what is normally their summer foraging grounds in the Amundsen Gulf and eastern Beaufort Sea. The underlying question is whether this is the leading edge of a phenological shift in a species' migratory behaviour in an environment undergoing dramatic shifts due to climate change.

Bowhead whales (Balaena mysticetus) in the western Beaufort Sea (west of 140°W, south of 72°N) exhibit considerable spatiotemporal variability in distribution, density, and behavior that can be largely explained by variability in feeding opportunities, both local and remote. Bowhead whale feeding opportunities are dynamic and ephemeral, dependent on interannual variability driven by biological and physical forces. These insights were made possible by multidisciplinary investigations centered around the Aerial Surveys of Arctic Marine Mammals (ASAMM, https://www.fisheries.noaa.gov/alaska/marine-mammal-protection/aerial-surveys-arctic-marine-mammals ) time series, a long-term (1979–2019) dataset of line-transect surveys in the western Beaufort and eastern Chukchi Seas conducted during summer (July–August) and autumn (September–October). Seasonal patterns of bowhead whale distribution and density in the western Beaufort Sea during two time periods, prior to 2000 and since 2000, are evident in spatially explicit models of relative density that were created using ASAMM data. These models illustrate a general transition in bowhead distribution toward shallower waters as the open-water season (July–October) progresses. Notably, however, the location and number of high-density areas and the timing of the spatial transition have shifted between the two periods. The association between bowhead whales and sea ice in the western Beaufort Sea is rather enigmatic, as exemplified by the similarities in bowhead whale distribution in autumn 2019 (when sea ice retreat was extensive) with the distribution observed when sea ice extent was heavy in the 1980s and 1990s. Anthropogenic factors also affect bowhead whale distribution and density. The effects of anthropogenic and environmental factors on bowheads may be confounded, especially lacking sufficient understanding of the underlying environmental variability inherent in the ecosystem. Variability is a defining characteristic of the Arctic, but the parameters appear to be changing, sometimes in unexpected ways. Improving our understanding and capacity to predict arctic variability is fundamentally important to sound natural resource management. It follows that sound natural resource management is founded on continued monitoring of the ecosystem so that our understanding of the ecological linkages that shape animal distributions and densities tracks the changes occurring, and expected to continue to occur, in the Arctic.

Bowheads, like other baleen whales, must find relatively high-density prey patches to feed efficiently. Bowhead whales feed primarily on small zooplankton such as copepods, euphausiids, mysids, and amphipods. Regardless of the stock, the annual migrations of bowhead whales to effective feeding areas have been the object of many research efforts. Data from satellite telemetry and/or observations from aircraft, shore, and research vessels by western scientists had been used to infer the diet and foraging ecology of the bowhead whales. Coastal bowhead whaling communities provide expert observations unavailable to western researchers, long-term indigenous knowledge, as well as make the whale accessible for examination and analyses to better understand the diet and foraging ecology of the bowhead whale during differing seasons and locations throughout the year. In this chapter we provide an overview of diet information for the bowhead stocks and provide detailed information diet and foraging insights for Bering–Chukchi–Beaufort (BCB) whales that includes historic and current knowledge of bowhead diet and foraging ecology obtained from the stomach contents, feces, and/or other tissues sampled from harvested bowheads. Insights are provided regarding emerging issues due to the ongoing and significant reduction in sea ice extent, quality, and duration and the resulting transitions to northern marine ecosystems, especially the BCB population.

Over the last 30 years, the use of telemetry, especially satellite telemetry, has improved our understanding of bowhead whale movements and behavior of the Bering-Chukchi-Beaufort (BCB) stock. Here, we summarize the findings of a collaboration between the Alaska Department of Fish and Game, the Alaska Eskimo Whaling Commission, the North Slope Borough, and Fisheries and Oceans Canada that deployed satellite tags (n=77) on bowhead whales during 2006–18. This study refined our knowledge of the distribution of BCB bowhead whales, especially outside the boundaries of aerial surveys and away from whaling communities. We found that whale movements are much more complex and wide-ranging than originally thought; for example, some whales that initially migrate to the Canadian Beaufort may return west in midsummer, sometimes traveling all the way to Russia and back to Canada prior to the autumn migration. Based upon whale behavior (i.e., the timing of movements and dive behavior) and the colocation of whales and oceanographic features that help aggregate prey, bowhead whales of the BCB stock likely feed year-round. We think the distribution of BCB bowhead whales is largely driven by food availability and that whales have spatial memory of where food was located in past years. Much of the data we collected on the distribution of BCB bowhead whales is already out of date, as environmental changes are altering the distribution of bowhead prey and sea ice.

The hunting of bowhead whales (Balaena mysticetus) is an integral part of Inuit culture. An up-to-date abundance estimate of the entire Eastern Canada – West Greenland (EC-WG) bowhead population is necessary to support sustainable management of this harvest. The High Arctic Cetacean Survey (HACS) was conducted in August 2013, primarily to update abundance estimates for known stocks of Baffin Bay narwhal (Monodon monoceros). As the ranges of narwhal and bowhead largely overlap, the survey area was expanded to cover the summer range of bowhead whales. Bowhead whale abundance was estimated using 3 aircraft to cover the large survey area within a short time frame. Distance sampling methods were used to estimate detection probability away from the track line. Double platform with mark-recapture methods were used to correct for the proportion of whales missed by visual observers on the track line (perception bias). Abundance in Isabella Bay, an area known for high bowhead density, was estimated using density surface modelling to account for its complex shape and uneven coverage. Estimates were corrected for availability bias (whales that were not available for detection because they were submerged when the aircraft passed overhead) using a recent analysis of satellite-linked time depth recorders transmitting information on the diving behaviour of bowhead whales in the study area in August of the same survey year. The fully corrected abundance estimate for the EC-WG bowhead whale population was 6,446 (95% CI: 3,838–10,827). Possible sources of uncertainty include incomplete coverage and the diving behaviour of bowhead whales. These results confirm earlier indications that the EC-WG stock is continuing to recover from past overexploitation.

Estimating abundance is one of the most fundamental and important aspects of population biology, with major implications on how the status of a population is perceived and thus on conservation and management efforts. Although typically based on one of two methods (distance sampling or mark-recapture), there are many individual identification methods that can be used for mark-recapture purposes. In recent years, the use of genetic data for individual identification and abundance estimation through mark-recapture analyses have increased, and in some situations such genetic identifications are more efficient than their field-based counterparts for population monitoring. One issue with mark-recapture analyses, regardless of which method of individual identification is used, is that the study area must provide adequate opportunities for “capturing” all individuals within a population. However, many populations are unevenly and widely distributed, making it unfeasible to adequately sample all necessary areas. Here we develop an analytical technique that accounts for unsampled locations, and provides a means to infer “missing” individuals from unsampled locations, and therefore obtain more accurate abundance estimates when it is not possible to sample all sites. This method is validated using simulations and is used to estimate abundance of the Eastern Canada-West Greenland (EC-WG) bowhead whale population. Based on these analyses, the estimated size of this population is 11,747 individuals during the sampling period, with a 95% highest density interval of 8,169–20,043.

The subpopulation of the bowhead whale Balaena mysticetus in the East Greenland-Svalbard-Barents Sea is endangered and until recently was believed to number in the tens. Recent studies have suggested that this subpopulation appears to be increasing. Here, we report on unusual aggregations of bowhead whales within the Fram Strait. We present opportunistic and effort-corrected observations of bowhead whales made from a small expedition vessel during cruises in June (2015-2018). Bowhead whales were sighted on 85 occasions (220-227 whales). An aggregation in 2015 (n = 84 whales) and high numbers in 2018 (n = 104-110) exceeded all previous records. The index of whale abundance was significantly higher in open water-leads (1.08-1.14 whales km-1 of survey effort) compared to areas with drift-ice (0.51-0.53 whales km-1). The highest abundance index was measured in deep waters where the bottom slope was relatively steep. Our findings highlight the temporal and spatial consistency of this species in areas with relatively loose ice cover (open water-leads) and steep slopes. It is unknown how global warming and resultant changes in ice-extent are going to affect bowhead whales within the Strait and whether they will find new feeding grounds due to an expanding open-ocean habitat. These slopes may become increasingly important to bowhead whales and Arctic top predators as a spring/early summer feeding ground. These relatively large numbers of bowhead whales are encouraging and can help direct future research monitoring programs to study the population ecology of these endangered whales.

After millennia of hunting and a population collapse, it is still challenging to understand the genetic consequences of whaling on the circumarctic bowhead whale. Here I use published modern mtDNA sequences from the Bering-Chukchi-Beaufort population and a new time calibration to show that late–glacial climate changes and whaling have been the major drivers of population change. Cultures that hunted in the Arctic Seas from as early as 5000 years ago appear to be responsible for successive declines of the population growth, bringing the effective size down to 38% of its pristine population size. The Thules and the Basques (year 1000–1730) who only hunted in the North Atlantic had a major impact on this North Pacific population, indicating that bowhead whale stocks respond to harvesting as a single population unit. Recent positive growth is inferred only after the end of commercial whaling in 1915, and for levels of harvesting that are close to the current annual quota of 67 whales. By unfolding the population history of the bowhead whale, I provide compelling evidence that mtDNA yields critical yet undervalued information for management and conservation of natural populations.

The range of the Bering-Chukchi-Beaufort (BCB) population of bowhead whales (Balaena mysticetus) extends across the seasonally ice-covered waters of the Pacific Arctic region. The majority of whales summer in the eastern Beaufort Sea and winter in the Bering Sea, migrating across the Chukchi Sea in fall and spring. As arctic sea-ice extent rapidly diminishes, the increasing length and variability of the open water season is changing bowhead habitat substantially, with many areas now regularly ice-free when whales are present. This study examines changes in the number of open water days (OWD) between 1979 and 2014 within annual bowhead whale core-use areas as defined by satellite tagging data, and within the western Beaufort Sea (140–157°W; to 72°N) sampled by fall aerial surveys. Ice cover has decreased more in the core-use areas in the northern extent of the range than in core-use areas in the southern extent. The numbers of OWD within the core-use areas near Point Barrow and along the northern Chukotka Coast during peak use have increased by 13 and 10 days/decade, respectively. The most dramatic reductions in sea-ice cover have taken place in the western Beaufort Sea where the number of OWD on the shelf and slope have increased by 20 and 25 days/decade, respectively. In contrast, sea-ice cover has not significantly changed within the winter core-use area near the Gulf of Anadyr. Using aerial survey data, we found that bowheads in the Beaufort Sea during the fall migration have a preference for being closer to shore than to the ice edge, and that their distance to shore decreases as the fraction of open water increases. This distribution may be due to increased feeding opportunities closer to shore as a result of greater upwelling along the shelf break when the ice cover is farther from shore. Furthermore, the aerial survey data also revealed a substantial shift westward toward Point Barrow in the whales’ use of the western Beaufort Sea during fall in the period 1997–2014 compared to 1982–1996. The extent and timing of sea-ice coverage has changed relatively little over time in the Bering Sea. Bowheads typically migrate north prior to spring ice melt and retreat; therefore, large changes in the timing of the spring migration are not expected. We anticipate that bowheads will spend increasingly more time within summer and fall feeding areas, delaying their arrival to wintering areas in the Bering Sea. Reduced ice coverage and thickness in the southern Chukchi Sea may make wintering there more common in the future. Summer and fall movements may be more variable as productivity and zooplankton aggregations in existing feeding areas are altered in response to sea ice thinning and retreat, and as new areas become available.

We collated available satellite telemetry data for six species of ice-associated marine mammals in the Pacific Arctic: ringed seals (Pusa hispida; n = 118), bearded seals (Erignathus barbatus, n = 51), spotted seals (Phoca largha, n = 72), Pacific walruses (Odobenus rosmarus divergens, n = 389); bowhead whales (Balaena mysticetus, n = 46), and five Arctic and sub-arctic stocks of beluga whales (Delphinapterus leucas, n = 103). We also included one seasonal resident, eastern North Pacific gray whales (Eschrichtius robustus, n = 12). This review summarized the distribution of daily locations from satellite-linked transmitters during two analysis periods, summer (May–November) and winter (December–April), and then examined the overlap among species. Six multi-species core use areas were identified during the summer period: 1) Chukotka/Bering Strait; 2) Norton Sound; 3) Kotzebue Sound; 4) the northeastern Chukchi Sea; 5) Mackenzie River Delta/Amundsen Gulf; and 6) Viscount Melville Sound. During the winter period, we identified four multi-species core use areas: 1) Anadyr Gulf/Strait; 2) central Bering Sea; 3) Nunivak Island; and 4) Bristol Bay. During the summer period, four of the six areas were centered on the greater Bering Strait region and the northwestern coast of Alaska and included most of the species we examined. The two remaining summer areas were in the western Canadian Arctic and were largely defined by the seasonal presence of Bering-Chukchi-Beaufort stock bowhead whales and Eastern Beaufort Sea stock beluga whales, whose distribution overlapped during both summer and winter periods. During the winter period, the main multi-species core use area was located near the Gulf of Anadyr and extended northwards through Anadyr and Bering Straits. This area is contained within the Bering Sea “green belt”, an area of enhanced primary and secondary productivity in the Bering Sea. We also described available telemetry data and where they can be found as of 2017. These data are important for understanding ice-associated marine mammal movements and habitat use in the Pacific Arctic and should be archived, with appropriate metadata, to ensure they are available for future retrospective analyses.

The acoustic environment of two focal Arctic species, bowhead (Balaena mysticetus) and beluga (Delphinapterus leucas) whales, varied among the three core-use regions of the Pacific Arctic examined during the months in which both species occur: (1) January-March in the St. Lawrence Island/Anadyr Strait region, (2) November-January in the Bering Strait region, and (3) August-October in the Barrow Canyon region. Biological noise (consisting of the signals of bowhead whales, walrus and bearded seals) dominated the acoustic environment for the focal species in the St. Lawrence Island/Anadyr Strait region, which was covered with ice throughout the months studied. In the Bering Strait region whales were exposed primarily to environmental noise (in the form of wind noise) during November, before the region was ice-covered in December, and biological noise (from bowhead and walrus) again was prevalent. Anthropogenic noise dominated the Barrow Canyon region for the focal species in late summer and fall (August through October); this was also the only region in which the two species did not overlap with sea ice. Under open water conditions both near Barrow Canyon and in Bering Strait, noise levels were tightly correlated with wind. However, with climate-change driven increases in open water leading to rising noise levels across multiple fronts (atmospheric, biological, anthropogenic), the relatively pristine acoustic environment of Arctic cetaceans is changing rapidly. Characterizing the acoustic habitat of these regions before they are further altered should be considered a management and conservation priority in the Arctic.

The data on sightings of the bowhead whale (Balaena mysticetus Linnaeus, 1758) in the western Sea of Okhotsk collected during eight field seasons, as well as information obtained from interviews with local residents in the study region, are presented. The major areas of concentration of the bowhead whale population in the ice-free period are determined; the whale behavior in bays is described. Data on sea surface temperature, salinity, and depth measurements at the sites of bowhead whale sightings are provided. The possible causes of whale concentrations close to the shoreline and in apical parts of mainland shallow-water bays, as well as the potential threats to the population associated, inter alia, with this pattern of distribution, are discussed.

Each spring, most Bowhead Whales (Balaena mysticetus) of the Bering-Chukchi-Beaufort (BCB) population migrate to the Canadian Beaufort Sea and Amundsen Gulf for summer feeding. Occasionally, Inuvialuit hunters and others observe beachcast (stranded) or adrift Bowhead Whale carcasses. From 1987 to 2016, 26 such occurrences were recorded. Most (65%) were found by Inuvialuit hunters travelling on the land, with the majority (54%) reported during 2000–2006. Bowhead Whale carcasses were found widely distributed throughout the region, with twice as many in Amundsen Gulf (65%) compared with the southeastern Beaufort Sea (35%). It was possible to measure or estimate standard length for 17 of 26 specimens, and all were either provisional ‘subadults’ (7–9.5 m; n = 10; 59%) or provisional ‘mature adults’ (13–16 m; n = 7; 41%). The cause(s) of mortality was not determined for any of the specimens. Whales in the ‘subadult’ group were likely 1–4 years old, while the ‘mature adult’ group were likely mostly mature animals (~25 y), including some potentially very old (>100 y). There was evidence or direct observation of Polar Bears (Ursus maritimus) and/or Grizzly Bears (U. arctos) scavenging at 60% of the carcasses for which presence or absence of bears or bear sign (scats and/or tracks) was reported. It is important to continue to record incidental observations of beachcast Bowhead Whales, as this may enable stranding rates to be evaluated.

Plasticity in the physiological and behavioural responses of animals to prolonged food shortages may determine the persistence of species under climate warming. This is particularly applicable for species that can “adaptively fast” by conserving protein to protect organ function while catabolizing endogenous tissues. Some Ursids, including polar bears (Ursus maritimus), adaptively fast during winter hibernation—and it has been suggested that polar bears also employ this strategy during summer. We captured 57 adult female polar bears in the Southern Beaufort Sea (SBS) during summer 2008 and 2009 and measured blood variables that indicate feeding, regular fasting, and adaptive fasting. We also assessed tissue δ13C and δ15N to infer diet, and body condition via mass and length. We found that bears on shore maintained lipid and protein stores by scavenging on bowhead whale (Balaena mysticetus) carcasses from human harvest, while those that followed the retreating sea ice beyond the continental shelf were food deprived. They had low ratios of blood urea to creatinine (U:C), normally associated with adaptive fasting. However, they also exhibited low albumin and glucose (indicative of protein loss) and elevated alanine aminotransferase and ghrelin (which fall during adaptive fasting). Thus, the ~ 70% of the SBS subpopulation that spends summer on the ice experiences more of a regular, rather than adaptive, fast. This fast will lengthen as summer ice declines. The resulting protein loss prior to winter could be a mechanism driving the reported correlation between summer ice and polar bear reproduction and survival in the SBS.

Since the first studies on bowhead whale singing behaviour, song variations have been consistently reported. However, there has been little discussion regarding variability in bowhead whale singing display and its ecological significance. Unlike the better studied humpback whales, bowhead whales do not appear to share songs at population level, but several studies have reported song sharing within clusters of animals. Over the winter season 2013–2014, in an unstudied wintering ground off Northeast Greenland, 13 song groups sharing similar hierarchical structure and units were identified. Unit types were assessed through multidimensional maps, showing well separated clusters corresponding to manually labelled units, and revealing the presence of unit subtypes. Units presented contrasting levels of variability over their acoustic parameters, suggesting that bowhead whales keep consistency in some units while using a continuum in values of frequency, duration and modulation parameters for other unit types. Those findings emphasise the need to account for variability in song analysis to better understand the behavioural ecology of this endangered species. Additionally, shifting from song toward units or phrase-based analysis, as it has been suggested for humpback whales, offers the opportunity to identify and track similarities in songs over temporal and geographical scales relevant to population monitoring.

Ecological baselines—reference states of species' distributions and abundances—are key to the scientific arguments underpinning many conservation and management interventions, as well as to the public support to such interventions. Yet societal as well as scientific perceptions of these baselines are often based on ecosystems that have been deeply transformed by human actions. Despite increased awareness about the pervasiveness and implications of this shifting baseline syndrome, ongoing global assessments of the state of biodiversity do not take into account the long-term, cumulative, anthropogenic impacts on biodiversity. Here, we propose a new framework for documenting such impacts, by classifying populations according to the extent to which they deviate from a baseline in the absence of human actions. We apply this framework to the bowhead whale ( Balaena mysticetus ) to illustrate how it can be used to assess populations with different geographies and timelines of known or suspected impacts. Through other examples, we discuss how the framework can be applied to populations for which there is a wide diversity of existing knowledge, by making the best use of the available ecological, historical and archaeological data. Combined across multiple populations, this framework provides a standard for assessing cumulative anthropogenic impacts on biodiversity. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

Interannual variability in euphausiid (krill) abundance and population structure and associations of those measures with environmental drivers were investigated in an 11-year study conducted in late August–early September 2005–2015 in offshelf waters (bottom depth > 40 m) in Barrow Canyon and the Beaufort Sea just downstream of Distributed Biological Observatory site 5 (DBO5) near Pt. Barrow, Alaska. Statistically-significant positive correlations were observed among krill population structure (proportion of juveniles and adults), the volume of Late Season Melt Water (LMW), and late-spring Chukchi Sea sea ice extent. High proportions of juvenile and adult krill were seen in years with larger volumes of LMW and greater spring sea ice extents (2006, 2009, 2012–2014) while the converse, high proportions of furcilia, were seen in years with smaller volumes of LMW and lower spring sea ice extent (2005, 2007, 2010, 2011, 2015). These different life stage, sea ice and water mass regimes represent integrated advective responses to mean fall and/or spring Chukchi Sea winds, driven by prevailing atmospheric pressure distributions in the two sets of years. In years with high proportions of juveniles and adults, late-spring and preceding-fall winds were weak and variable while in years with high proportions of furcilia, late-spring and preceding-fall winds were strong, easterly and consistent. The interaction of krill life history with yearly differences in the northward transports of krill and water masses along with sea ice retreat determines the population structure of late-summer krill populations in the DBO5 region near Pt. Barrow. Years with higher proportions of mature krill may provide larger prey to the Pt. Barrow area bowhead whale prey hotspot. The characteristics of prey near Pt. Barrow is dependent on krill abundance and size, large-scale environmental forcing, and interannual variability in recruitment success of krill in the Bering Sea.

The distribution of the Bering-Chukchi-Beaufort Sea population of bowhead whales (Balaena mysticetus) is largely centered in the Chukchi Sea in autumn (September–November), which is also when sea ice is at minimum extent allowing for increased ship traffic and industrial activity. Prior work paired autumn movements of bowhead whales in the Chukchi Sea with simulated hydrographic information and concluded whales followed relatively cold, saline waters of Pacific origin during migration (

Polar bear (Ursus maritimus) subpopulations in several areas with seasonal sea ice regimes have shown declines in body condition, reproductive rates, or abundance as a result of declining sea ice habitat. In the Foxe Basin region of Nunavut, Canada, the size of the polar bear subpopulation has remained largely stable over the past 20 years, despite concurrent declines in sea ice habitat. We used fatty acid analysis to examine polar bear feeding habits in Foxe Basin and thus potentially identify ecological factors contributing to population stability. Adipose tissue samples were collected from 103 polar bears harvested during 2010–2012. Polar bear diet composition varied spatially within the region with ringed seal (Pusa hispida) comprising the primary prey in northern and southern Foxe Basin, whereas polar bears in Hudson Strait consumed equal proportions of ringed seal and harp seal (Pagophilus groenlandicus). Walrus (Odobenus rosmarus) consumption was highest in northern Foxe Basin, a trend driven by the ability of adult male bears to capture large‐bodied prey. Importantly, bowhead whale (Balaena mysticetus) contributed to polar bear diets in all areas and all age and sex classes. Bowhead carcasses resulting from killer whale (Orcinus orca) predation and subsistence harvest potentially provide an important supplementary food source for polar bears during the ice‐free period. Our results suggest that the increasing abundance of killer whales and bowhead whales in the region could be indirectly contributing to improved polar bear foraging success despite declining sea ice habitat. However, this indirect interaction between top predators may be temporary if continued sea ice declines eventually severely limit on‐ice feeding opportunities for polar bears.

Information about the occurrence of marine mammals near the Colville River Delta (CRD), Beaufort Sea, Alaska is limited for most species expected to occur in this region. As part of marine mammal monitoring and mitigation for a seismic acquisition program August 25–September 30, 2014, we recorded marine mammal occurrence in a ~ 30 km2 survey area between the Spy Islands and Oliktok Point near Simpson Lagoon using a combination of visual and acoustic monitoring methods. Visual effort totaled 632 h, occurring 18–20 h/day during all daylight hours by observers aboard three small survey vessels. In addition, an Inupiat observer and seal hunter from the village of Nuiqsut conducted a small-vessel survey to investigate locations of Phoca largha haul-out sites. A total of 102 individual marine mammals were recorded from five species: P. largha, Pusa hispida, Ursus maritimus, Erignathus barbatus, and Delphinapterus leucas. Over 400 h of acoustic data were recorded using second-generation Ecological Acoustic Recorders deployed on the seafloor at three locations. Calls were identified for D. leucas, Balaena mysticetus, E. barbatus, and P. hispida. Results provide valuable information on marine mammal occurrence for the Beaufort Sea CRD during summer/fall, an area proposed for potential offshore oil and gas development.

Climate change is impacting the subsistence livelihoods of many indigenous communities in the Arctic. We describe how structured decision analysis (SDA), informed by traditional ecological knowledge, can be used to understand the mechanisms of how climate change influences subsistence species and their harvest, and to build upon existing adaptive strategies and decision-making processes. In the Iñupiat community of Wainwright, Alaska, we test SDA as a potential framework by which vulnerabilities of subsistence systems can be identified and climate change adaptations can be prioritized. Over the course of five workshops, participants identified issues of concern, assessed the benefits and trade-offs of different strategies to enhance the safety of subsistence activities, identified factors influencing key subsistence species and their accessibility, and assessed the dependence of animals and their harvest on sea ice. Furthermore, we asked workshop participants to assess whether subsistence resources have increased, decreased, or remained stable over the past decade. Declining caribou populations and unsafe ice conditions for hunters were of particular concern in Wainwright. Participants identified high priority safety strategies such as a new docking facility, safety workshops, a hunter meeting place, and search and rescue boats. Because of its coastal location on a lagoon at the mouth of a river, Wainwright has a highly diverse subsistence system that may in part buffer the negative effects of climate change. Furthermore, most species or groups harvested in Wainwright were assessed as stable or increasing. Nevertheless, of the five most important subsistence species in Wainwright, one experienced recent population declines (caribou) and the harvest of three others depends on the presence of thick, reliable shorefast ice. We propose that SDA can be a useful tool to assess the vulnerability of subsistence systems to climate change, and can be used to prioritize strategies to adapt to climate change.

The effects of climate change constitute a major concern in Arctic waters due to the rapid decline of sea ice, which may strongly alter the movements and habitat availability of Arctic marine mammals. We tracked 98 bowhead whales by satellite over an 11-year period (2001–2011) in Baffin Bay - West Greenland to investigate the environmental drivers (specifically sea surface temperature and sea ice) involved in bowhead whale’s movements. Movement patterns differed according to season, with aggregations of whales found at higher latitudes during spring and summer likely in response to sea-ice retreat and increasing sea temperature (SST) facilitated by the warm West Greenland Current. In contrast, the whales moved further south in response to sea temperature decrease during autumn and winter. Statistical models indicated that the whales targeted a narrow range of SSTs from −0.5 to 2 °C. Sea surface temperatures are predicted to undergo a marked increase in the Arctic, which could expose bowhead whales to both thermal stress and altered stratification and vertical transport of water masses. With such profound changes, bowhead whales may face extensive habitat loss. Our results highlight the need for closer investigation and monitoring in order to predict the extent of future distribution changes.

We analyzed data from line-transect aerial surveys for marine mammals conducted in the western Beaufort Sea (shore to 72˚ N, 140˚–157˚ W) from July to October of 2009–16 to investigate the distribution, behaviors, sighting rates, and habitat use preferences of bowhead and beluga whales. The habitat use data allowed for direct comparison with data collected in the same area from 1982 to 1991. Both species are ice-adapted, migrating through leads in sea ice in spring, and are seasonal inhabitants of the western Beaufort Sea during summer and fall. From 2009 to 2016, bowheads were seen in all survey months, with the highest overall sighting rate (whales per km) in August. Bowhead sighting rates were highest in the whales’ preferred habitats: outer shelf habitat (51–200 m depth) in July and inner shelf-shallow habitat (≤ 20 m depth) in August, September, and October. Beluga whales were also seen in all survey months, with highest overall sighting rate in July. Beluga whales were overwhelmingly associated with continental slope habitat (201–2000 m depth) in all months. Bowhead distribution and depth preferences in summer months of 2009–16 differed from those observed in 1982–91, when bowheads were not seen during limited survey effort in July and preferred outer continental shelf habitat in August. These differences indicate that bowhead whale preference for shallow shelf habitat now occurs earlier in summer than it used to. Beluga distribution and depth preference remained similar between 1982–91 and 2009–16, with strong preference for continental slope during both periods. Differences in sea ice cover habitat association for both species are likely due more to the relative lack of sea ice in recent years compared to the earlier period than to shifts in habitat preference. Habitat partitioning between bowhead and beluga whales in the western Beaufort Sea remained evident except in July, when both species used continental slope habitat. In July – October 2009–16, the distribution, sighting rates, and behavior of both bowheads and belugas in the western Beaufort showed considerable interannual variation, which underscores the importance of annual sampling to accurate records of the complex western Beaufort Sea ecosystem.

Reduction of summer sea ice extent has led some polar bear (Ursus maritimus) populations to increase their use of land during the summer/autumn open-water period. While terrestrial food resources are generally not sufficient to compensate for lost hunting opportunities on the sea ice, marine mammal carcasses, where available, could help reduce the energetic cost of longer periods of land use. Subsistence-harvested bowhead whale (Balaena mysticetus) remains are available annually near local communities along the Alaskan portion of the Beaufort Sea coast to bears that come to shore. Relatively large numbers of polar bears and some grizzly bears (U. arctos) use these resources, creating a competitive environment among species and social classes. We documented competitive interactions among polar bears and between polar and grizzly bears for bowhead whale remains adjacent to a small community in northeastern Alaska in September 2005–2007. We observed temporal partitioning of the resource by bears, with lone a...

Bowhead whales, Balaena mysticetus, in the Bering–Chukchi–Beaufort (BCB) population, experience a variable acoustic environment among the regions they inhabit throughout the year. A total of 41,698 h of acoustic data were recorded from 1 August 2009 through 4 October 2010 at 20 sites spread along a 2300 km transect from the Bering Sea to the southeast Beaufort Sea. These data represent the combined output from six research teams using four recorder types. Recorders sampled areas in which bowheads occur and in which there are natural and anthropogenic sources producing varying amounts of underwater noise. We describe and quantify the occurrence of bowheads throughout their range in the Bering, Chukchi, and Beaufort seas over a 14-month period by aggregating our acoustic detections of bowhead whale sounds. We also describe the spatial–temporal variability in the bowhead acoustic environment using sound level measurements within a frequency band in which their sounds occur, by dividing a year into three, 4-month seasons (Summer–Fall 2009, August–November 2009: Winter 2009–2010, December 2009–March 2010: and Spring–Summer 2010, April–July 2010) and their home range into five zones. Statistical analyses revealed no significant relationship between acoustic occurrence, distance offshore, and water depth during Summer–Fall 2009, but there was a significant relationship during Spring–Summer 2010. A continuous period with elevated broadband sound levels lasting ca. 38 days occurred in the Bering Sea during the Winter 2009–2010 season as a result of singing bowheads, while a second period of elevated levels lasting at least 30 days occurred during the early spring–summer season as a result of singing bearded seals. The lowest noise levels occurred in the Chukchi Sea from the latter part of November into May. In late summer 2009 very faint sounds from a seismic airgun survey approximately 700 km away in the eastern Beaufort Sea were detected on Chukchi recorders. Throughout the year, but most obviously during the November into May period, clusters of intermittent, nearly synchronized, high-level events were evident on multiple recorders hundreds of miles apart. In some cases, these clusters occurred over 2–5 day periods and appear to be associated with high wind conditions.

We examined the response of bowhead whale (Balaena mysticetus) body condition to summer sea ice conditions and upwelling-favorable winds. We used a long-term dataset collected from whales of the Bering–Chukchi–Beaufort Seas (BCB) stock to estimate various body condition indices (BCI’s) for individual whales that were harvested by Alaskan Eskimos. A series of offshore regions frequented by bowhead whales in summer were delineated and used to quantify interannual summertime environmental conditions including: (a) mean open water fraction, (b) duration of melt season, (c) date of continuous freeze-up, and (d) mean upwelling-favorable wind stress. Body condition was analyzed relative to these metrics for both the preceding summer feeding season and the previous three seasons combined. Our analysis indicates a significant increase in the long-term trend in an axillary girth-based body condition index (BCIG) over the study period (1989–2011). The increase in BCIG is likely associated with the trend in overall reduction of sea ice, including increased duration of open water, changes in upwelling potential (wind stress), and possibly higher primary production in the Pacific Arctic marine ecosystem favoring water-column invertebrates. We found strong significant positive correlations between BCIG and late summer open water fraction in the Beaufort Sea and smaller nearshore areas off the Mackenzie Delta and west of Banks Island. Additionally, BCIG was positively and significantly correlated with duration of melt season, later date of freeze-up in the Beaufort Sea, and upwelling-favorable winds on the Mackenzie shelf and west of Banks Island. A strong seasonal difference in BCI’s was noted for subadult bowheads, presumably associated with summer feeding; however, yearlings were found to drop in BCI over at least the first summer after weaning. Our results indicate an overall increase in bowhead whale body condition and a positive correlation with summer sea ice loss over the last 2.5 decades in the Pacific Arctic. We speculate that sea ice loss has positive effects on secondary trophic production within the BCB bowhead’s summer feeding region. While not part of this study, the abundance of BCB bowheads increased markedly over the same period.

An analysis of the stable isotopes of oxygen (δ18O) and hydrogen (δD) was used to examine the linkage between sea ice concentration and the migration of western arctic bowhead whales (Balaena mysticetus; WABW). We compared δ18O and δD variability along the length of WABW baleen with isotopic values of zooplankton prey from different WABW habitat, with published δ13C and δ15N data, and with historical sea ice records. Zooplankton signatures varied widely (δ18O = −13‰–56‰; δD = −220‰ to −75‰), with regional separation between winter (Bering Sea) and summer (eastern Beaufort Sea) habitats of WABW observable in δD. The δ18O and δD of WABW varied significantly along the length of baleen (δ18O = 8–18‰; δD = −180 to −80‰), confirming seasonal migration and reflecting distinct regional dietary variation in isotopes. WABW migration appears to have varied concomitant with temporal sea ice concentration (SIC) changes; in years with high SIC, the difference in δD of WABW baleen between seasonal habitats was significantly greater than low SIC periods. This work shows that SIC is not only a determinant of habitat accessibility for WABW, but baleen may also be a record of historical SIC and Arctic climate.

The critically endangered Spitsbergen stock of bowhead whale (Balaena mysticetus) seems to be increasing. However, research effort has also been increasing confounding a firm conclusion. A systematic aerial survey for walrus (Odobaenus rosmarus), applying distance sampling methodology in part of the Northeast Water Polynya (NEW), revealed a ‘bycatch’ of several observations of bowhead whales, which resulted in an estimated abundance of 102 (95 % CI 32–329) individuals. This is the largest abundance of bowhead whales reported from the Greenland Sea since the days of whaling in the sixteenth to seventeenth centuries. The NEW was inaccessible to vessels during the whaling period because of heavy pack ice, and it is only recently that researchers have visited this area; thus only a few sightings of bowhead whales within the NEW exist prior to the survey in 2009. The NEW may nevertheless be one of the most important summering grounds for the Spitsbergen stock, and the whales may benefit from advection of calanoid copepods from the productive deep basins along the coast of Svalbard east of the NEW. This discovery provides renewed hope for the Spitsbergen stock of bowhead whales that until now has shown only inconclusive signs of recovery despite more than 100 years of protection from whaling.

Almost all mammals communicate using sound, but few species produce complex songs. Two baleen whales sing complex songs that change annually, though only the humpback whale ( Megaptera novaeangliae ) has received much research attention. This study focuses on the other baleen whale singer, the bowhead whale ( Balaena mysticetus ). Members of the Spitsbergen bowhead whale population produced 184 different song types over a 3-year period, based on duty-cycled recordings from a site in Fram Strait in the northeast Atlantic. Distinct song types were recorded over short periods, lasting at most some months. This song diversity could be the result of population expansion, or immigration of animals from other populations that are no longer isolated from each other by heavy sea ice. However, this explanation does not account for the within season and annual shifting of song types. Other possible explanations for the extraordinary diversity in songs could be that it results either from weak selection pressure for interspecific identification or for maintenance of song characteristics or, alternatively, from strong pressure for novelty in a small population.

Polar bear (Ursus maritimus) diet may become more variable in some Arctic regions due to climate warming and altered sea ice habitat. We surveyed carbon and nitrogen stable isotope profiles of five polar bear tissues sampled from adult females in the Southern Beaufort Sea of Alaska in order to assess inter-tissue isotopic variability and to determine whether any dietary shifts are occurring in this population. We did not detect any significant shifts from historical means in population-level tissue stable isotope values. A number of sectioned hair samples, however, were significantly depleted in 15N relative to the mean. We hypothesized that lower hair δ15N values were due to the consumption of bowhead whale (Balaena mysticetus) tissue. Telemetry data showed that polar bears with 15N-depleted hair sections were located on multiple dates near known subsistence-harvested bowhead whale bone piles and had spent 90 % of the prior year within 50 km of the shore. Bears with hair section δ15N values at or above the mean spent no time near bowhead whale bone piles and less than half of the year nearshore. An isotopic mixing model estimation of diet proportions determined that bowhead whale comprised approximately 50–70 % of fall diet for bears with lower hair δ15N values. We conclude that these results offer emergent evidence of an alternative foraging strategy within this population: ‘coastal’ bears, which remain near to shore for much of the year and use bowhead whale bone piles when they are present. In contrast, ‘pelagic’ bears follow a more typical strategy and forage widely on sea ice for seals.

In the Arctic, warming and concomitant reductions in sea ice will affect the underwater soundscape, with the greatest changes likely being linked to anthropogenic activities. In this study, an acoustic recorder deployed on an oceanographic mooring in western Fram Strait documented the soundscape of this area, which is important habitat for the Critically Endangered Spitsbergen bowhead whale population. The soundscape was quasi-pristine much of the year, with low numbers of ships traversing the area. However, during summer/autumn, signals from airgun surveys were detected >12h/day. Mean received peak-to-peak SPLs for loud airgun pulses reached 160.46±0.48dB 1μPa when seismic-survey ships were close (at ~57km). Bowhead whales were present almost daily October-April in all years, with singing occurring in almost every hour November-March. Currently, loud anthropogenic sound sources do not temporally overlap the peak period of bowhead singing. This study provides important baseline data for future monitoring.

During summer 2012 Shell performed exploratory drilling at Sivulliq, a lease holding located in the autumn migration corridor of bowhead whales (Balaena mysticetus), northwest of Camden Bay in the Beaufort Sea. The drilling operation involved a number of vessels performing various activities, such as towing the drill rig, anchor handling, and drilling. Acoustic data were collected with six arrays of directional recorders (DASARs) deployed on the seafloor over ~7 weeks in Aug-Oct. Whale calls produced within 2 km of each DASAR were identified and localized using triangulation. A "tone index" was defined to quantify the presence and amplitude of tonal sounds from industrial machinery. The presence of airgun pulses originating from distant seismic operations was also quantified. For each 10-min period at each of the 40 recorders, the number of whale calls localized was matched with the "dose" of industrial sound received, and the relationship between calling rates and industrial sound was modeled using negative binomial regression. The analysis showed that with increasing tone levels, bowhead whale calling rates initially increased, peaked, and then decreased. This dual behavioral response is similar to that described for bowhead whales and airgun pulses in earlier work. Increasing call repetition rates can be a viable strategy for combating decreased detectability of signals arising from moderate increases in background noise. Meanwhile, as noise increases, the benefits of calling may decrease because information transfer becomes increasingly error-prone, and at some point calling may no longer be worth the effort.

As a precautionary measure to protect the culturally-significant bowhead whale ( Balaena mysticetus ) from vessel strike, this paper explores the potential for having the International Maritime Organization endorse ships׳ routeing measures in the Bering Strait region. The confined nature of the Bering Strait forces both vessel traffic and the migrating Bering–Chukchi–Beaufort stock of bowhead whales to occupy the same narrow space, thus putting individual animals at risk of vessel strike. The potential for vessel strike may become exacerbated as the reduction of Arctic sea ice makes the Arctic increasingly accessible, allowing vessels to transit through the Strait in greater densities. In drawing from lessons learned in the successful reduction of vessel strike to the North Atlantic right whale ( Eubalaena glacialis ), the author provides broad recommendations for implementing ships׳ routeing measures in the Bering Strait region based on findings by Citta et al. (2012). It is recommended that both the western side of Big Diomede Island and the western side of St. Lawrence Island be designated as seasonal Areas To Be Avoided (ATBA) during fall months when bowheads are known to inhabit the area. Alternatively, it is proposed that Traffic Separation Schemes (TSSs) be implemented so that vessels must keep to the eastern side of both Big Diomede Island and St. Lawrence Island during this time. Both measures would reduce the amount of overlap between migrating bowhead whales and transiting vessel traffic, effectively reducing the potential for vessel strike.

We contrast two methods for estimating the trends of bowhead whales (Balaena mysticetus) in West Greenland: (1) double platform visual aerial survey, corrected for missed sightings and the time the whales are available at the surface; and (2) a genetic capture-recapture approach based on a 14-yr-long biopsy sampling program in Disko Bay. The aerial survey covered 39,000 km2 and resulted in 58 sightings, yielding an abundance estimate of 744 whales (CV = 0.34, 95% CI: 357–1,461). The genetic method relied on determining sex, mitochondrial haplotypes and genotypes of nine microsatellite markers. Based on samples from a total of 427 individuals, with 11 recaptures from previous years in 2013, this resulted in an estimate of 1,538 whales (CV = 0.24, 95% CI: 827–2,249). While the aerial survey is considered a snapshot of the local spring aggregation in Disko Bay, the genetic approach estimates the abundance of the source of this aggregation. As the whales in Disko Bay primarily are adult females that do not visit the bay annually, the genetic method would presumably yield higher estimates. The studies indicate that an increase in abundance observed between 1998 and 2006 has leveled off.

Radiocarbon-dated marine mammal remains from emergent Arctic coastlines have frequently been used to reconstruct Holocene sea-ice histories. The use of such reconstructions has hitherto been complicated by uncertain marine reservoir corrections precluding meaningful intercomparisons with data reported in calibrated or sidereal years. Based on an exhaustive compilation of previously published marine mammal radiocarbon dates (both live-harvested materials and subfossils) from the Canadian Arctic Archipelago (CAA), new, statistically-derived δ13C and ΔR values are provided. Average δ13C values are: −16.1 ± 1.1‰ (bone collagen; n = 193) for bowhead (Balaena mysticetus); −14.4 ± 0.5‰ (n = 44; dentine) for beluga (Delphinapterus leucas); −14.8 ± 1.9‰ (teeth and tusks; n = 18) and −18.0 ± 4.7‰ (n = 9; bone collagen) for walrus (Odobenus rosmarus). ΔR values are 170 ± 95 14C years for bowhead (n = 23) and 240 ± 60 14C years for beluga (n = 12). Scarce data preclude calculation of meaningful, statistically robust walrus ΔR. Using the new ΔR values, an expanded and revised database of calibrated bowhead dates (651 dates; many used in previous CAA sea-ice reconstructions) shows pronounced late Quaternary spatio-temporal fluctuations in bone abundance. Though broadly resembling earlier bowhead subfossil frequency data, analysis of the new expanded database suggests early- and mid-Holocene increases in whale abundance to be of longer duration and lower amplitude than previously considered. A more even and persistent spread of infrequent low-abundance remains during “whale free” intervals is also seen. The dominance of three eastern regions (Prince Regent Inlet & Gulf of Boothia; Admiralty Inlet; Berlinguet Inlet/Bernier Bay) in the CAA data, collectively contributing up to 88% of all subfossil remains in the mid-Holocene, is notable. An analysis of calibrated regional sea-level index points suggests that severance of the Admiralty Inlet-Gulf of Boothia marine channel due to isostatically-driven regression may have played a significant role in enhanced whale mortality during this interval. Comparisons between the newly calibrated bowhead data and other regional sea-ice proxy data further highlight spatial and temporal discrepancies, potentially due to regional asynchronicities and variable sensitivities in proxy response to climate and oceanographic forcing. However, the limited number of deglacial–postglacial marine records continues to hamper extensive intercomparisons between marine mammal and other proxy datasets. Nevertheless, an examination of assumptions inherent in linking bowhead subfossil frequencies, population densities, and sea-ice thickness and distribution, shows that such relationships are highly complex. Factors such as broad sea-ice preferences, variable mortality rates and causes, long distance carcass transport, variable coastline and basin/channel geometries, and changing emergence rates all complicate the correlation of whale bone abundance to sea-ice histories.

Estimation of Arctic marine mammal presence and acoustic density from passive acoustic monitoring is complicated by effects of the environment and noise levels on sound propagation and the detection of calls. We used acoustic modeling and detection simulations to estimate site-specific transmission loss for sounds produced by bowhead whales in the northeast Chukchi Sea at two sites, outer shelf and continental slope, with and without sea ice cover at various ocean noise levels. A time series of hourly acoustic detection probability was produced for the two recording sites between 2012 and 2013 from modeled transmission loss for daily sea ice state and hourly average noise levels. We applied the detection probability to recorded bowhead whale call detections to correct for effects of ice cover and noise level. Corrected acoustic presence suggests a decrease in detectable calls within a 40 km radius of the recording sites with arrival of open water while the uncorrected detections increase or change little. When sea ice state is constant, substantial variability in acoustic presence tracks closely with changing noise levels. These results highlight the importance of incorporating effects of the environment and changing noise levels when interpreting results of passive acoustic monitoring.

Biophysical changes in marine ecosystems of the Arctic and subarctic sectors of the Atlantic and Pacific are now evident, driven primarily by sea ice loss, ocean warming and increases in primary productivity. As upper trophic species, baleen whales can serve as sentinels of ecosystem reorganization in response to these biophysical alterations, via changes in their ecology and physiological condition. This paper is the first to review baleen whale ecology in high-latitude marine ecosystems of both the north Atlantic and north Pacific. Oceanographically, these sectors offer four contrasting habitats to baleen whales: (i) a broad-deep-strait and deep-shelf inflow system in the Northeast Atlantic (NEA), (ii) a combination of inflow and outflow systems north of Iceland in the central North Atlantic (CNA), (iii) an outflow shelf and basin in the Northwest Atlantic (NWA), and (iv) a narrow-shallow-strait inflow shelf system in the Pacific sector. Information on baleen whale ecology from visual and passive acoustic surveys, combined with available telemetry and diet studies, show contrasting patterns of baleen whale occurrence among sectors. In brief, arctic and subarctic waters in the Atlantic sector support a far greater number of seasonally-migrant baleen whales than the Pacific sector. Thousands of humpback, fin and common minke whales occupy the diverse habitats of the Atlantic sector. These species all exhibit flexible diets, focused primarily on euphausiids (krill) and forage fishes (e.g., capelin, herring, sand lance), which are now responding to ecosystems altered by climate change. Conversely, the Pacific sector supports a far greater number of arctic-endemic bowhead whales than the Atlantic sector, as well as a large population of seasonally-migrant gray whales. Currently, differences in migratory timing and, to a lesser extent, foraging behaviors, serves to restrict prey competition between the arctic-endemic bowhead whale and seasonally migrant baleen whale species in both sectors. Regional aspects of changes in prey type and availability will likely impact future migratory timing, habitat selection, body condition and diet of baleen whales. Tracking variability in these attributes can provide valuable input to ecosystem models and thereby contribute the sentinel capability of baleen whales to forecasts of future states of high latitude marine ecosystems.