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Real recordings of bowhead whale signals and numerical simulation were used to investigate the propagation of such signals in an Arctic-type shallow-water waveguide. The authors analyzed attenuation and distortion of whale signals with increasing distance in the following conditions: (1) a soft and hard bottom, (2) different whale depths, (3) surface waves, (4) additive noise, and (5) reception by a single hydrophone and a vertical array. Signal attenuation was estimated by the change in sound pressure level (SPL). Signal distortion was estimated by the change in the correlation coefficient for the spectrograms of received signals and the reference spectrograms. It is shown that, compared to signals from a single receiver, the attenuation and distortion characteristics of the array output signals are more stable and resistant to changes in whale depth, to possible, under Arctic conditions, significant variations in sound speed in the bottom along the acoustic path, and to the effects of additive noise. The results can be used for passive monitoring of bowhead whales on the Arctic shelf. [ABSTRACT FROM AUTHOR]

Significant effort has been made over the last few decades to develop automated passive acoustic monitoring (PAM) systems capable of classifying cetaceans at the species level. The utility of such systems depends on the systems' ability to operate across a wide range of ocean acoustic environments; however, anecdotal evidence suggests that site-specific propagation characteristics impact the performance of PAM systems. Variability in propagation characteristics leads to differences in how each cetacean vocalization is altered as it propagates along the source-receiver path. A propagation experiment was conducted in the Gulf of Mexico to investigate the range-dependent impacts of acoustic propagation on the performance of an automated classifier. Modified bowhead and humpback vocalizations were transmitted over ranges from 1 to 10 km. When the classifier was trained with signals collected near the sound source, it was found that the performance decreased with increasing transmission range—this appeared to be largely explained by decreasing signal-to-noise ratio (SNR). Generation of performance matrices showed that one method to develop a classifier that maintains high performance across many ranges is to include a varied assortment of ranges in the training data; however, if the training set is limited, it is best to train on relatively low SNR vocalizations. [ABSTRACT FROM AUTHOR]

The present study aims at an improved understanding of the origin and distribution of bowhead whales (Balaena mysticetus) along the Norwegian coast during Late Pleistocene/Holocene. We used ancient DNA methodology to identify the species of 52 large whale bones found along the coast of the Norwegian mainland. Nucleotide sequence variation of the mitochondrial control region (CR) was determined and subsequently screened against GenBank for species identification. Thirty-one bones (60%) yielded informative nucleotide sequences for the targeted mitochondrial CR. Of these, 24 matched with bowhead whale. Two additional bones were identified to bowhead whale based on morphology. Thus, 26 of the bones were identified to be from bowhead whales. The ages of the bowhead bones ranged from 15,084 cal years BP to present, with most bones older than 10,000 cal years BP. We suggest that our results show a change in distribution of bowhead whales from the very southern Norwegian Sea in the Heinrich Stadial 1 (19,000-14,600 years BP) to a distribution reaching 64°N in the Bølling-Allerød Interstadial (14,600-12,900 years BP), while the species probably was absent along the Norwegian coast during the cold Younger Dryas (12,900-11,700 years BP). During the Holocene, the species most likely has had only a northern distribution. The present study does not contribute new knowledge to solve the question if North Atlantic bowhead whales originated from a refugium in the southeast Atlantic during the Last Glacial Maximum or originate from the Pacific. [ABSTRACT FROM AUTHOR]

The external auditory meatus (EAM) in many species of mysticete whales is filled with a waxy ear plug. Though this lamellated structure is often used to age a whale, its formation and development remain undescribed. It is thought that growth layer groups (GLGs) are laid down annually, thereby increasing the size of this structure. Since some mysticete whales are migratory and many undergo molting, we hypothesized that the cyclical production of these GLGs may be related to these processes. The epithelia of both EAM and glove finger (a part of the tympanic membrane protruding into the EAM) of one juvenile and multiple adult bowhead whales from both fall (October: non‐molting) and spring (May: molting) seasons were dissected and examined anatomically and histologically. These tissue samples were compared with the adult oral epithelia at the same time periods. These epithelia shared a similar basic broad structure, though there were differences in thickness and presence of intraepithelial structures. All epithelia in the October specimens were rich in both glycogen and lipid. The parakeratinized epithelium of the oral cavity in the juvenile and some May specimens shed via the production of several superficial epithelial fissures. Other adult May specimens exhibited deep epithelial fissures, reminiscent of pressure ulcers, which would cause the detachment of the entire epithelium from the dermis. We propose that sloughed epithelial lining is the source of the GLGs in the ear plug. Correlating a potential molting sequence with these observations explained the presence of epidermal glycogen, deep epidermal fissures and dermal glycolipid, and to some extent calls into question the origin and structure of the ear plug itself. Further morphological characterization of ear plugs in bowheads is needed to better understand cell origin and ear plug formation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The embryology of cetaceans documents features that elucidate the interaction between form and function in modern species, as well as their evolution from extinct ones. Prenatal specimens of the dolphin Stenella attenuata demonstrate critical aspects of the embryonic and fetal development of cetaceans, the pharyngeal arches, ear ossicles, nasal opening, teeth, fore limb, hind limb, and flukes. In addition, specimens of the bowhead whale (Balaena mysticetus) illustrate the development of baleen and hair. [ABSTRACT FROM AUTHOR]

Abstract Vessel traffic has been increasing rapidly in the Arctic, and within the Canadian Arctic, tourist vessels are the fastest growing maritime sector. Vessel traffic can cause a variety of impacts on whales, including ship strikes and acoustic disturbance. Here, the overlap between tourist vessels (e.g., pleasure craft/yachts and passenger vessels/cruise ships) and whale concentration areas is assessed within the Inuvialuit Settlement Region of the western Canadian Arctic. Different management measures which could be used to reduce impacts on whales are also assessed. Passenger vessels have had a relatively constant overlap with whale concentration areas through time, whereas pleasure craft have had a recent and rapid increase. Passenger vessels may have a greater impact on whales, compared to pleasure craft, since they are larger and travel faster. Excluding vessels from the two marine protected areas in the region would have no impact on whales within concentration areas, since vessels would likely just be displaced to adjacent areas with similar whale concentrations. Restricting vessels to the Canadian government's proposed low-impact corridor may reduce impact slightly, but creating a corridor completely outside of the known whale area could more significantly reduce the potential impact of vessels on whales in those areas. Restricting vessel speed within whale areas would also reduce the impact of passenger vessels, but would not likely reduce the impact of pleasure craft. Overall, a combination of management measures may be the best way to reduce impacts on whales in concentration areas. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that the analysis of biogeochemical tracers along baleen can provide seasonal, annual, and longer term insights into whale movements, habitat use, diet, and ecosystem processes. We measured the mercury (Hg) concentration and stable carbon (δ13C) and nitrogen (δ15N) isotope compositions along baleen plates of bowhead whales (Balaena mysticetus) harvested between 1988 and 1996 from the Bering-Chukchi-Beaufort (BCB) and the Eastern Canada-West Greenland (EC-WG) populations. These measurements were compared among individuals and between populations to assess seasonal cycling and to determine if bowhead whales forage year-round rather than fasting in winter. Individuals from the BCB population had synchronous cycles with higher Hg concentrations and lower δ13C values in summer and lower Hg concentrations and higher δ13C values in winter. EC-WG individuals also had synchronized periodic variations with peak values in isotopic ratios during summer. These results reflect an annual cycle of seasonal migration between distinct food webs in both populations. Spring and fall feeding activity was indicated in the intra-annual Hg and δ13C cycles along the baleen plates of all whales in our study. These shorter periods, spanning about half the annual growth, have not been previously described in the baleen of these populations, and are consistent with separate foraging areas along the migration routes. The results of this study provide further support for year-round foraging in a species previously thought to fast during winter. Future monitoring of seasonal foraging patterns in baleen would help to determine whether bowhead whales alter their foraging patterns in response to shifts in zooplankton community availability, composition, and phenology. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

Abstract Each fall, bowhead whales in the Bering-Chukchi-Beaufort (BCB) population migrate westward from summering grounds in the Beaufort Sea through the Chukchi Sea to the northern coast of Chukotka, Russia. Routes whales use when crossing the Chukchi Sea vary by year; in some years, whales migrate directly to the northern coast of Chukotka while in other years, whales may pause migration and linger, presumably to feed, in the central Chukchi Sea. To investigate how whale movements may be related to oceanographic variables we examined bowhead whale habitat selection within the Chukchi Sea in autumn (September--November) at two spatial scales. First, at the landscape scale (i.e. the Chukchi Sea), we compare oceanographic variables (e.g. temperature, salinity, and current velocity) at locations within used and randomly available tracks (i.e. paths of travel) to determine how oceanographic features are associated with where whales cross the Chukchi Sea in autumn. Second, at a local scale, we examine how directed travel or lingering within a whale's track is associated with oceanographic variables (e.g. temperature, salinity, and current velocity). Whale location data for 24 bowhead whales were paired with oceanographic data from a pan-arctic coupled ice-ocean model for 2006–2009. At the landscape scale, we found that whales generally followed water of Pacific origin characterized by temperatures <0ºC and salinities between 31.5 and 34.25. Bowhead whales avoided Alaskan Coastal Water and Siberian Shelf Water, the latter of which defines the western limit of their range, likely due to lower intrinsic densities of zooplankton prey. At the local scale, within their tracks, whales were more likely to interrupt directed movements and linger in areas characterized by stronger gradients in bottom salinity. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

Abstract Aerial surveys for bowhead whales have been conducted with a relatively consistent methodology over the Alaskan Beaufort Sea since 1989. Sightings of bowhead whales in the central Alaskan Beaufort Sea in September 1997 and September 2014 were unusual in that hundreds of whales were observed within a few kilometers of local barrier islands. We compare bowhead whale sightings, river discharge data, wind records, and satellite imagery to argue that the large numbers of bowhead whales observed nearshore in September 1997 and 2014 resulted from favorable feeding conditions established by high river discharges and prior upwelling events. These results are then generalized in a simple binary-based mechanistic framework that links the relevant physics to occurrences of observed and potential feeding opportunities for bowhead whales in the central Alaskan Beaufort Sea and in other locales along the Beaufort coast. [ABSTRACT FROM AUTHOR]

Bowhead whales generally migrate into high Arctic waters in the summer months and move to lower latitudes in the wintertime. During the 1800s and early 1900s commercial whaling greatly reduced the numbers of bowhead whales in waters adjacent to the North Atlantic Ocean. In recent decades their numbers have been increasing. Thirteen sightings of a bowhead whale were recorded in four areas of the Gulf of Maine in 2012, 2014, and 2017 between latitudes 44°43'N and 41°36'N, far south of the normal range (54°N) for this species. Photographs obtained during these sightings were compared by experienced photo analysts and, based on scarring patterns, the sightings were confirmed to be of the same individual. The bowhead whale was observed alone, in addition to interacting in a social group and engaged in coordinated feeding with other mysticetes at times. The feeding and social behaviour of the bowhead whale was typical for the species but well south of its normal Arctic waters range and in the absence of conspecifics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Tympanic bullae and baleen plates from bowhead whales of the Western Arctic population were examined. Growth layer groups (GLGs) in the involucrum of the tympanic bone were used to estimate age of the whales, and compared to stable isotope signatures along transects of baleen plates and the involucrum. The involucrum of the tympanic bone consists of three regions that form in utero, during nursing in the first year, and during the first decades of life, respectively. Life history events, such as annual migration, are recorded in the bowhead tympanic bulla. It is likely that bone growth in the bowhead tympanic occurs during periods of high food intake, while slow or arrested growth occurs during periods of low food intake. Comparisons between numbers of GLGs in the tympanic, number of isotopic oscillations in a baleen plate, length of the baleen plate, and total whale length show correlation coefficients as high as 0.97. The tympanic GLG method is particularly useful for estimating the age of whales up to 20 yr old. [ABSTRACT FROM AUTHOR]

Bowhead whales (Balaena mysticetus) have a nearly circumpolar distribution, and occasionally occupy warmer shallow coastal areas during summertime that may facilitate molting. However, relatively little is known about the occurrence of molting and associated behaviors in bowhead whales. We opportunistically observed whales in Cumberland Sound, Nunavut, Canada with skin irregularities consistent with molting during August 2014, and collected a skin sample from a biopsied whale that revealed loose epidermis and sloughing. During August 2016, we flew a small unmanned aerial system (sUAS) over whales to take video and still images to: 1) determine unique individuals; 2) estimate the proportion of the body of unique individuals that exhibited sloughing skin; 3) determine the presence or absence of superficial lines representative of rock-rubbing behavior; and 4) measure body lengths to infer age-class. The still images revealed that all individuals (n = 81 whales) were sloughing skin, and that nearly 40% of them had mottled skin over more than two-thirds of their bodies. The video images captured bowhead whales rubbing on large rocks in shallow, coastal areas—likely to facilitate molting. Molting and rock rubbing appears to be pervasive during late summer for whales in the eastern Canadian Arctic. [ABSTRACT FROM AUTHOR]

Epidermal molting in the bowhead whales that regularly enter Ulbanskiy Bay of the Sea of Okhotsk in summer has been reported and proven by histological methods. Longitudinal delamination and detachment of thin or thick sheets of a considerable area have been established for the surface layer (stratum externum) of the whale epidermis during molting. A correlation of molting intensity to the level of proliferation and regeneration of all epidermal layers has been noted and assumed to stabilize the thickness of the skin. The phenomenon of molting is discussed from the viewpoint of adaptation of the whales to the conditions of the shallow bays of the Sea of Okhotsk that warm up thoroughly in the summer. [ABSTRACT FROM AUTHOR]

Climate change is causing physical and biological changes in the polar marine environment, which may impact higher trophic level predators such as the bowhead whale ( Balaena mysticetus) and the structure of their food webs. We used bulk stable isotope analysis and compound-specific isotope analysis (CSIA) of individual amino acids (AA) to examine bowhead whale trophic position and the biogeochemistry of one of their feeding grounds, Disko Bay, West Greenland, over a period of 7 years (2007-2013). We also examined whether environmental conditions such as sea ice concentration and sea surface temperature were causing any interannual variation in isotope data. Bulk δ N values were consistent across the 7 years of sampling and were similar between sex classes. Bulk δ C and essential-AAs δ C values displayed an overall temporal decline of 1.0 and 1.4‰, respectively. A significant positive linear relationship was found between δ C of bulk skin and essential-AAs suggesting that some of the observed isotopic variation in bowhead whales between years reflect changes in the carbon at the base of the food web. There were no correlations between the δ C and δ N values of isotopic tracers with sea ice concentrations or sea surface temperatures. The trophic level of bowhead whales remained stable over time despite large interannual variability in ice and temperature regimes. Our results indicate that the recent environmental changes in West Greenland resulted in no trophic perturbation being transferred to bowhead whales during that time period. Our study shows that the novel approach of CSIA-AA can be used effectively to study the combined temporal variation of bowhead whale food web structure and ecosystem isotopic baseline values and detect changes at the species and ecosystem levels. [ABSTRACT FROM AUTHOR]