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Population genetic research is a critical tool for the conservation and management of marine mammals and other species. The bowhead whale (Balaena mysticetus) is subject to aboriginal subsistence hunting in Alaska, Canada, Chukotka, and Greenland and managed by the International Whaling Commission for all those countries except Canada. Genetic studies support conservation management plans and the determination of safe hunting quotas by providing information on levels of genetic diversity, estimates of abundance and effective population size, and stock separation. Because bowhead populations are monitored in several countries, including genetic monitoring, there is a need for methods that can be consistently used in multiple labs that provide comparable data that can be publicly shared and built upon by successive studies. Here we present a new panel of single nucleotide polymorphisms (SNPs), derived from multiple bowhead populations, that meet those criteria. We describe the use of the Fluidigm SNPtype assay for analyzing 69 autosomal, 6 X-chromosome, and 1 Y-chromosome SNPs. Results indicate that the methods herein are reliable and have low error rates. Because SNPs are discrete sequence-based genetic markers, the panel of loci described here can be replicated, used in different labs, and are directly comparable, making SNPs more useful than existing microsatellite markers.

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.

In a species of baleen whale, we identify olfactory epithelium that suggests a functional sense of smell and document the ontogeny of the surrounding olfactory anatomy. Whales must surface to breathe, thereby providing an opportunity to detect airborne odorants. Although many toothed whales (odontocetes) lack olfactory anatomy, baleen whales (mysticetes) have retained theirs. Here, we investigate fetal and postnatal specimens of bowhead whales (Balaena mysticetus). Computed tomography (CT) reveals the presence of nasal passages and nasal chambers with simple ethmoturbinates through ontogeny. Additionally, we describe the dorsal nasal meatuses and olfactory bulb chambers. The cribriform plate has foramina that communicate with the nasal chambers. We show this anatomy within the context of the whole prenatal and postnatal skull. We document the tunnel for the ethmoidal nerve (ethmoid foramen) and the rostrolateral recess of the nasal chamber, which appears postnatally. Bilateral symmetry was apparent in the postnatal nasal chambers. No such symmetry was found prenatally, possibly due to tissue deformation. No nasal air sacs were found in fetal development. Olfactory epithelium, identified histologically, covers at least part of the ethmoturbinates. We identify olfactory epithelium using six explicit criteria of mammalian olfactory epithelium. Immunohistochemistry revealed the presence of olfactory marker protein (OMP), which is only found in mature olfactory sensory neurons. Although it seems that these neurons are scarce in bowhead whales compared to typical terrestrial mammals, our results suggest that bowhead whales have a functional sense of smell, which they may use to find prey.

The cetacean visual system is a product of selection pressures favoring underwater vision, yet relatively little is known about it across taxa. Previous studies report several mutations in the opsin genetic sequence in cetaceans, suggesting the evolutionary complete or partial loss of retinal cone photoreceptor function in mysticete and odontocete lineages, respectively. Despite this, limited anatomical evidence suggests cone structures are partially maintained but with absent outer and inner segments in the bowhead retina. The functional consequence and anatomical distributions associated with these unique cone morphologies remain unclear. The current study further investigates the morphology and distribution of cone photoreceptors in the bowhead whale and beluga retina and evaluates the potential functional capacity of these cells' alternative to photoreception. Refined histological and advanced microscopic techniques revealed two additional cone morphologies in the bowhead and beluga retina that have not been previously described. Two proteins involved in magnetosensation were present in these cone structures suggesting the possibility for an alternative functional role in responding to changes in geomagnetic fields. These findings highlight a revised understanding of the unique evolution of cone and gross retinal anatomy in cetaceans, and provide prefatory evidence of potential functional re-assignment of these cells. This article is protected by copyright. All rights reserved.

Aerial line transect surveys were conducted during 19 July – 20 August in each of the years 2012 – 17, with onshore – offshore transects covering a study area of approximately 110 000 km2, from 140˚ W to 157˚ W longitude and from shore to 72˚ N latitude. These data were used to estimate abundance of the eastern Chukchi Sea (ECS) stock of beluga whales. The data were stratified based on bathymetry to reflect strong large-scale gradients in beluga density. A half-normal key function was used to model detection from a dataset of 999 sightings of 2465 belugas. The detection function was found to depend significantly on sky condition and ice coverage. For the years 2012 through 2017, respectively, the estimated numbers of ECS belugas in the study area during the study period were 7355 (CV = 0.17), 6813 (CV = 0.18), 16 598 (CV = 0.21), 6456 (CV = 0.21), 6965 (CV = 0.23) and 13 305 (CV = 0.27). There is no statistically significant trend. These estimates do not correct for belugas outside the study region. Indeed, diverse data indicate that belugas venture far outside the study region and their distribution varies interannually due to prey availability and other factors. Recently reviewed tagging data suggest that correcting for whales outside the study area would approximately double our abundance estimates. These results provide no indication that the stock has substantially declined during these six years due to the impact of subsistence hunting, industrial activity or climate change, although interannual variation and estimated CVs are both large, thereby potentially masking small-scale impacts.

The external acoustic meatus (EAM) of most baleen whales accumulates cellular debris annually in the lumen as whales age, forming a lamellated ear plug. The bowhead whale ear plug is formed from annually molting lining of the EAM as the entire epithelium releases at the level of the stratum basale during the spring migration. Epithelial regeneration is mostly completed by the fall migration, remaining intact for 6-7 months before being torn off the following spring. Desmosomes are integral to cell-cell adhesion with connecting desmosomal cadherins desmoglein (dsg) and desmocollin (dsc). Paraffin sections of the oral cavity and EAM lining of spring and fall adult bowhead whales, as well as the EAM of spring-caught juvenile, were immunohistochemically examined for the presence of these cadherins. In all fall specimens, both cadherins occurred in all layers except the superficial keratinous layer of the oral cavity. In spring, three different conditions existed: (a) oral cavity of spring-caught adults had reduced cadherins, with superficial fissuring in its keratinized layer and vacuolation in the upper stratum spinosum; (b) EAM of juvenile spring-caught whales displayed fissuring with accompanying reduction of both cadherins in its superficial lining; and (c) EAM lining of spring-caught adults displayed deep fissures, reduced cadherins, and absence of dsc1 in the fissuring zone. These results suggest that shedding of skin layers in mammals, whether normal molting, pathological, or the result of injury and wound repair all revolve around desmosome function. The specific role, structure, and location of these two cadherins need to be further addressed.

The current subsistence harvest of bowhead whales (Balaena mysticetus) allows Inuit from Greenland, Canada, Alaska, and Chukotka to help fill important nutritional and cultural needs. Greenland and Canada primarily hunt from the East Canada–West Greenland stock and Alaska and Chukotka hunt from the Bering–Chukchi–Beaufort (BCB) Seas stock. There is no hunting on the Spitzbergen and Sea of Okhotsk stocks. The hunts for bowheads in Greenland, Canada, and Chukotka are small, numbering only one or two per year. The hunts on the BCB stock are considerably larger with a landed quota of 56 whales per year. The quota is established by the International Whaling Commission based on the cultural and nutritional needs of Inuit communities and on the population size and trend of bowheads. Data on harvested BCB whales have been collected since the mid-1970s. Between 1974 and 2018, hunters from 12 villages in Alaska, extending from the Bering Sea to the eastern Alaskan Beaufort Sea, harvested 1493 bowheads. Hunters at Barrow landed the most whales (n=748), while Shaktoolik only landed one and Little Diomede landed two. Some villages hunt only in the spring, some only in the autumn, while Barrow, Wainwright, and the Saint Lawrence Island villages (Gambell and Savoonga) hunt in both the spring and autumn/winter. The average size of whales differs among the villages. Gambell, Savoonga, and Wainwright harvest larger whales than do Point Hope and Barrow. It is not clear whether these differences are due to hunter selectivity, whale availability, or both. The size of landed whales changes during the migration in at least some villages. During the spring, larger whales tend to be taken more frequently near the end of the migration. The opposite is true for the autumn whereby larger whales tend to be taken early while small whales tend to be taken later. Overall, the sex ratio is equal. Generally, males and females do not appear to segregate during the spring or autumn migration. However, large females appear to comprise much of the tail end of the migration as they tend to be more common in late May in northern Chukchi Sea. The efficiency (no. of whales landed/no. of whales struck) of the hunt has increased markedly over this period. Currently, the efficiency is about 0.80. The bowhead harvests in West Greenland, Canada, Chukotka, and Alaska represent only a fraction of the estimated population size, indicating that the hunts are sustainable.

The postcranial skeleton of bowhead whales was described in detail more than 100 years ago. The musculature of bowheads has not been studied in detail but matches that of other mysticetes in general features. In this chapter, we focus on some aspects of the skeleton that differs from that of other cetaceans. First, the skeleton of bowheads changes with ontogenetic age. Some of these changes are gross-morphologically, while others are biochemical and histological. Several are related to the life history of the species. Our discussion focuses on the changes in the morphology of the cervical vertebral column, the ontogenetic variation in carpals, and the variation in the hind limb. Individuals with external hind limbs occur infrequently, but there is a great variation in the size of ox coxae, femur, and tibia.

Bering–Chukchi–Beaufort Sea bowhead whales are born at about 4.2 m in length and 1000 kg, in lead systems along the NW Alaskan coast. Bowheads in the other northern stocks are also born in ice-covered seas. Maximum body lengths (standard measure) can reach 19 m. Regarding coloration: the skin is gray on neonates and young calves, and black on yearlings and adults. The size and shape of the chin patch is variable and does not change through life. After adulthood age, the specific areas of the skin lose pigment and turn white around the eye, the peduncle, genital groove, and base of the pectoral limb. Growth is rapid from birth to age 1, followed by a 3- to 4-year growth hiatus. Following the hiatus, the increase in body length is slow to sexual maturity at ~25 years and ~13.5 m in length. The Inupiat recognize several growth forms associated with age; these include aġvaaq (neonate), ingutuq (yearling), qairaliq (postyearling), along with several names for large adults. Allometry of the head is marked and likely associated with extreme development of the baleen rack. The head is very large in relation to body—perhaps the largest in Mammalia. The blubber is among the thickest of any cetacean (to ~38 cm). Body mass is similar to right whales of similar length; large bowheads can reach 100 metric tons or larger. Longevity can reach 200 or more years. The age of physical maturity is unclear, and adults may increase in length through life. Their ability to navigate ice-covered seas and break through ice to breathe is singular among baleen whales.

Recent years have seen rapid development of tools and approaches to model population consequences of disturbance in several marine mammal populations from high-amplitude, acute sound sources. Ocean noise from shipping and other maritime activities is now recognized as a chronic, habitat-level stressor. In order to understand population consequences of chronic ocean noise to whales and their populations, advances are needed in several key areas, which are explored in this review. One tractable way to predict population-level consequences of noise-mediated disruption of feeding, which can include both behavioural responses and foraging opportunities lost due to acoustic masking. Masking may be defined as both the process and the amount by which the threshold of hearing of one sound is raised by the presence of another. Parameterising any such model requires information on sensitivity and vulnerability of large whales to ocean noise, in which sensitivity is the degree to which marine features respond to a stressor (e.g., behavioural responses to noise or proportional reduction in foraging efficiency due to masking), and vulnerability is the probability that whales are exposed noise to which they are sensitive. Efforts are underway to provide much-needed information on hearing sensitivity in baleen whales, the role of acoustic cues in foraging, and deriving links between long-term variability in prey availability and whale demography. As this information becomes available, we expect rapid advancement on modelling population consequences of acoustic masking in baleen whales, because those efforts can leverage substantial investments in statistical methodological approaches to model population consequences of disturbance. Pathways of effects other than via foraging disruption (e.g., stress hormones affecting reproduction or disease) are possible, but we illustrate potential ways to proceed based on this tractable approach, namely noise-mediated impacts on foraging. This report highlights case studies of local, national, international, and inter-governmental efforts to monitor and reduce the contribution of global shipping to ocean ambient noise. The following outlines approaches that can be used to assess the risk to baleen whale recovery of existing levels of ocean noise, and consequently, predict the benefits likely to arise from reducing chronic ocean noise.

Evolutionary explanations for mammalian sociality typically center on inclusive-fitness benefits of associating and cooperating with close kin, or close maternal kin as in some whale societies, including killer and sperm whales. Their matrilineal structure has strongly influenced the thinking about social structure in less well-studied cetaceans, including beluga whales. In a cross-sectional study of group structure and kinship we found that belugas formed a limited number of distinct group types, consistently observed across populations and habitats. Certain behaviours were associated with group type, but group membership was often dynamic. MtDNA-microsatellite profiling combined with relatedness and network analysis revealed, contrary to predictions, that most social groupings were not predominantly organized around close maternal relatives. They comprised both kin and non-kin, many group members were paternal rather than maternal relatives, and unrelated adult males often traveled together. The evolutionary mechanisms that shape beluga societies are likely complex; fitness benefits may be achieved through reciprocity, mutualism and kin selection. At the largest scales these societies are communities comprising all ages and both sexes where multiple social learning pathways involving kin and non-kin can foster the emergence of cultures. We explore the implications of these findings for species management and the evolution of menopause.

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) were disposed directly into the Saguenay River of the St. Lawrence Estuary (SLE) by local aluminum smelters (Quebec, Canada) for 50 years (1926-1976). PAHs in the river sediments are likely etiologically related to gastrointestinal epithelial cancers observed in 7% of 156 mature (>19-year old) adult beluga found dead along the shorelines. Because DNA adduct formation provides a critical link between exposure and cancer induction, and because PAH-DNA adducts are chemically stable, we hypothesized that SLE beluga intestine would contain PAH-DNA adducts. Using an antiserum specific for DNA modified with several carcinogenic PAHs, we stained sections of paraffin-embedded intestine from 51 SLE beluga (0-63 years), 4 Cook Inlet (CI) Alaska beluga (0-26 years), and 20 beluga (0-46 years) living in Arctic areas (Eastern Beaufort Sea, Eastern Chukchi Sea, Point Lay Alaska) and aquaria, all with low PAH contamination. Stained sections showed nuclear light-to-dark pink color indicating the presence of PAH-DNA adducts concentrated in intestinal crypt epithelial lining cells. Scoring of whole tissue sections revealed higher values for the 51 SLE beluga, compared with the 20 Arctic and aquarium beluga (P = 0.003). The H-scoring system, applied to coded individual photomicrographs, confirmed that SLE beluga and CI beluga had levels of intestinal PAH-DNA adducts significantly higher than Arctic and aquarium beluga (P = 0.003 and 0.02, respectively). Furthermore, high levels of intestinal PAH-DNA adducts in four SLE beluga with gastrointestinal cancers, considered as a group, support a link of causality between PAH exposure and intestinal cancer in SLE beluga. Environ. Mol. Mutagen. 60:29-41, 2019. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

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.

A small colony of nesting Lesser Snow Geese (Chen caerulescens caerulescens) was discovered on the Ikpikpuk River delta in 1992. The number of nesting pairs averaged 35 (Range = 0–60) from 1992 to 1998, then increased dramatically from 176 in 1999 to 12,373 in 2015, for a λ of 1.40 (SE = 0.138). Concomitant with this dramatic population increase, the geographic extent of the colony expanded annually from three small islands in the northwestern portion of the delta during 1992–1999 to all vegetated deltaic islands in 2001 and farther inland on the mainland from 2006 onward. When colony growth was most rapid (2001–2008), nesting success averaged 79% (Range = 48–97%). Low nesting success during 2009–2014 (< 50% in all years except one), primarily caused by brown bears (Ursus arctos), was followed in 2015 by 96.6% success. In 2015, ∼22,000 adults (in both brood-rearing and adult-only flocks) were accompanied by more than 25,000 goslings in July and August. These numbers represent a remarkable increa...

In utero, baleen whales initiate the development of several dozens of teeth in upper and lower jaws. These tooth germs reach the bell stage and are sometimes mineralized, but toward the end of prenatal life they are resorbed and no trace remains after birth. Around the time that the germs disappear, the keratinous baleen plates start to form in the upper jaw, and these form the food‐collecting mechanism. Baleen whale ancestors had two generations of teeth and never developed baleen, and the prenatal teeth of modern fetuses are usually interpreted as an evolutionary leftover. We investigated the development of teeth and baleen in bowhead whale fetuses using histological and immunohistochemical evidence. We found that upper and lower dentition initially follow similar developmental pathways. As development proceeds, upper and lower tooth germs diverge developmentally. Lower tooth germs differ along the length of the jaw, reminiscent of a heterodont dentition of cetacean ancestors, and lingual processes of the dental lamina represent initiation of tooth bud formation of replacement teeth. Upper tooth germs remain homodont and there is no evidence of a secondary dentition. After these germs disappear, the oral epithelium thickens to form the baleen plates, and the protein FGF‐4 displays a signaling pattern reminiscent of baleen plates. In laboratory mammals, FGF‐4 is not involved in the formation of hair or palatal rugae, but it is involved in tooth development. This leads us to propose that the signaling cascade that forms teeth in most mammals has been exapted to be involved in baleen plate ontogeny in mysticetes.

Migrations are often influenced by seasonal environmental gradients that are increasingly being altered by climate change. The consequences of rapid changes in Arctic sea ice have the potential to affect migrations of a number of marine species whose timing is temporally matched to seasonal sea ice cover. This topic has not been investigated for Pacific Arctic beluga whales (Delphinapterus leucas) that follow matrilineally maintained autumn migrations in the waters around Alaska and Russia. For the sympatric Eastern Chukchi Sea (‘Chukchi’) and Eastern Beaufort Sea (‘Beaufort’) beluga populations, we examined changes in autumn migration timing as related to delayed regional sea ice freeze-up since the 1990s, using two independent data sources (satellite telemetry data and passive acoustics) for both populations. We compared dates of migration between ‘early’ (1993–2002) and ‘late’ (2004–2012) tagging periods. During the late tagging period, Chukchi belugas had significantly delayed migrations (by 2 to >4 weeks, depending on location) from the Beaufort and Chukchi seas. Spatial analyses also revealed that departure from Beaufort Sea foraging regions by Chukchi whales was postponed in the late period. Chukchi beluga autumn migration timing occurred significantly later as regional sea ice freeze-up timing became later in the Beaufort, Chukchi, and Bering seas. In contrast, Beaufort belugas did not shift migration timing between periods, nor was migration timing related to freeze-up timing, other than for southward migration at the Bering Strait. Passive acoustic data from 2008 to 2014 provided independent and supplementary support for delayed migration from the Beaufort Sea (4 day yr−1) by Chukchi belugas. Here, we report the first phenological study examining beluga whale migrations within the context of their rapidly transforming Pacific Arctic ecosystem, suggesting flexible responses that may enable their persistence yet also complicate predictions of how belugas may fare in the future.

Beluga whales ( Delphinapterus leucas ) are the most abundant cetacean in the Arctic. The Barrow Canyon region, Alaska, is a hotspot for Pacific Arctic belugas, likely because the oceanographic environment provides reliable foraging opportunities. Fronts are known to promote the concentration of planktonic prey; when Barrow-area winds are weak or from the west, a front associated with the Alaskan Coastal Current (ACC) intensifies. This front is weakened or disrupted when strong easterly winds slow or displace the ACC. To determine if winds influence the diving depth of belugas, we used generalized linear mixed models (GLMM) to examine how the dive behavior of animals instrumented with satellite-linked time-depth recorders varied with wind conditions. When projected along-canyon winds are from the WSW and the front associated with the ACC is enhanced, belugas tend to target shallower depths (10–100 m) associated with the front. In contrast, when strong winds from the ENE displaced the ACC, belugas tended to spend more time at depths >200 m where the Arctic halocline grades into relatively warmer Atlantic Water (AW). The probability of diving to >200 m, the number of dives >200 m, and the amount of time spent below 200 m were all significantly related to along-canyon wind stress ( p

Orbital glands are found in many tetrapod vertebrates, and are usually separate structures, consisting of individual glands lying in the eyelids and both canthi of the orbit. In cetaceans, however, the orbital glandular units are less distinct and have been described by numerous authors as a single, periorbital mass. There are few histochemical and immunhistochemical studies to date of these structures. In this study, we examined the orbital glandular region of both the bowhead whale (Balaena mysticetus: Mysticeti) and the beluga whale (Delphinapterus leucas: Odontoceti) using histological, histochemical, and immunohistochemical techniques. Histologically, in the bowhead, three glandular areas were noted (circumorbital, including Harderian and lacrimal poles), palpebral (midway in the lower eyelid), and rim (near the edge of the eyelid). In the beluga, there was only a large, continuous mass within the eyelid itself. Histochemical investigation suggests neither sexual dimorphism nor age-related differences, but both whales had two cell types freely intermingling with each other in all glandular masses. Large cells (cell type 1) were distended by four histochemically distinct intracellular secretory granules. Smaller cells (cell type 2) were not distended (fewer granules) and had two to three histochemically distinct intracellular secretory granules. The beluga orbital glands had additional lipid granules in cell type 1. Counterintuitively, both lipocalin and transferrin were localized to cell type 2 only. This intermingling of cell types is unusual for vertebrates in whom individual orbital glands usually have one cell type with one to two different secretory granules present. The heterogeneity of the orbital fluid produced by cetacean orbital glands implies a complex function, or series of functions, for these orbital glands and their role in producing the tear fluid.

The health implications of increasing exposure of marine mammals to environmental and anthropogenic stressors have been of major concern, warranting a better understanding of underlying physiology. This study screened gene expression profiles of ten stress and immune-related biomarkers using real-time polymerase chain reaction in both wild and aquarium belugas, reporting their reference ranges. Blood (n = 75) and skin (n = 73) samples were collected from wild belugas following live capture–release health assessments during 2008, 2012–2014 in Bristol Bay (58.86°N, 158.70°W), and subsistence hunts during 2012–2014 in Eastern Chukchi Sea (69.75°N, 163.05°W) in Alaska. Blood samples were also collected from five aquarium belugas (41.3733°N, 71.9533°W) in Mystic, Connecticut, under behavioral control. Live-captured whales showed significant (p

We report on the first beluga whale (Delphinapterus leucas), an adult female, from the Eastern Chukchi Sea (ECS) stock to be tagged with a Satellite Relay Data Logger (SRDL) that included a miniaturized Conductivity, Depth, and Temperature (CTD) sensor capable of collecting temperature (T) and salinity (S) profiles as the beluga dove. Prior work speculated that ECS belugas may target fronts and stratified regimes between water masses, because these boundaries may aggregate zooplankton, which in turn may attract fish that belugas prey upon. However, the SRDLs used in those studies were not capable of collecting CTD data necessary to identify water masses. The CTD-SRDL transmitted for 71 days, 8 July–17 September 2019, providing 492 time-depth profiles, indicating the shape and duration of beluga dives, and 255 CTD profiles, providing information on the location of water masses and ocean stratification used by the animal. We found that this beluga typically targeted fronts and stratified layers between water masses or colder water masses of Pacific origin. Of particular significance, we found that within the main summering area in Barrow Canyon, dives were co-located with the frontal zone between relatively warm and fresh Alaskan Coastal Water (derived from river discharge), and colder, saltier water of Pacific origin.

Little is known about the postnatal development of the physiological characteristics that support breath-hold in cetaceans, despite their need to swim and dive at birth. Arctic species have the additional demand of avoiding entrapment while navigating under sea ice, where breathing holes are patchily distributed and ephemeral. This is the first investigation of the ontogeny of the biochemistry of the locomotor muscle in a year-round Arctic-dwelling cetacean (beluga whale, Delphinapterus leucas). Compared with what we know about other cetaceans, belugas are born with high myoglobin content (1.56±0.02 g 100 g−1 wet muscle mass, N=2) that matures rapidly. Myoglobin increased by 452% during the first year after birth and achieved adult levels (6.91±0.35 g 100 g−1 wet muscle mass, N=9) by 14 months postpartum. Buffering capacity was 48.88±0.69 slykes (N=2) at birth; adult levels (84.31±1.38 slykes, N=9) were also achieved by 14 months postpartum. As the oxygen stores matured, calculated aerobic dive limit more than doubled over the first year of life, undoubtedly facilitating the movements of calves under sea ice. Nonetheless, small body size theoretically continues to constrain the diving ability of newly weaned 2 year olds, as they only had 74% and 69% of the aerobic breath-hold capacity of larger adult female and male counterparts. These assessments enhance our knowledge of the biology of cetaceans and provide insight into age-specific flexibility to alter underwater behaviors, as may be required with the ongoing alterations in the Arctic marine ecosystem associated with climate change and increased anthropogenic activities.

At least five populations (stocks) of beluga whales (Delphinapterus leucas) are thought to winter in the Being Sea, including the Bristol Bay, Eastern Bering Sea (Norton Sound), Anadyr, Eastern Chukchi Sea, and Eastern Beaufort Sea (Mackenzie) populations. Belugas from each population have been tagged with satellite-linked transmitters, allowing us to describe their winter (January–March) distribution. The objectives of this paper were to determine: (1) If each population winters in the Bering Sea, and if so, where? (2) Do populations return to the same area each year (i.e., are wintering areas traditional)? (3) To what extent do the winter ranges of different populations overlap? Tagged belugas from all five populations either remained in, or moved into, the Bering Sea and spent the winter there. Each population wintered in a different part of the Bering Sea and populations with multiple years of data (four of five) returned to the same regions in multiple years. When data were available from two populations that overlapped in the same year, they did not occupy the shared area at the same time. Although our sample sizes were small, the evidence suggests belugas from different populations have traditional winter ranges that are mostly exclusive to each population.

The objective of this paper is to report on the demography and pathology of 131 Pacific walruses (Odobenus rosmarus divergens), primarily calves, found dead on the northwest coast of Alaska in September 2009. The walrus carcasses extended over approximately 120 km, but most were found where walruses had hauled out for several days on the beach at Icy Cape. The remote location and severe weather made access to the site difficult and limited the number and extent of necropsies. A total of 71 carcasses were examined: nine were necropsied, and 62 were classified externally for age, gender, blubber depth, and other parameters. The most likely causes of death were crushing trauma, particularly of the upper thorax, neck and head, or asphyxiation due to being trampled by larger animals.

This work was supported in part by a contract between BP Exploration (Alaska) Inc. and the University of California, Santa Barbara (E.F.), and by the North Slope Borough. Potential responses of marine mammals to anthropogenic underwater sound are usually assessed by researchers and regulators on the basis of exposure to a single, relatively loud sound source. However, marine mammals typically receive sounds from multiple, dynamic sources. We developed a method to aggregate modeled sounds from multiple sources and estimate the sound levels received by individuals. To illustrate the method, we modeled the sound fields of 9 sources associated with oil development and estimated the sound received over 47 d by a population of 10 000 simulated bowhead whales Balaena mysticetus on their annual migration through the Alaskan Beaufort Sea. Empirical data were sufficient to parameterize simulations of the distribution of individual whales over time and their range of movement patterns. We ran 2 simulations to estimate the sound exposure history and distances traveled by bowhead whales: one in which they could change their movement paths (avert) in response to set levels of sound and one in which they could not avert. When animals could not avert, about 2% of the simulated population was exposed to root mean square (rms) sound pressure levels (SPL) ≥ 180 dB re 1 mu Pa, a level that regulators in the U.S. often associate with injury. When animals could avert from sound levels that regulators often associate with behavioral disturbance (rms SPL > 160 dB re 1 μPa)

Gross morphology and morphometry of the bowhead whale ovary, including ovulatory corpora, were investigated in 50 whales from the Chukchi and Beaufort seas off the coast of Alaska. Using the presence of ovarian corpora to define sexual maturity, 23 sexually immature whales (7.6-14.2 m total body length) and 27 sexually mature whales (14.2-17.7 m total body length) were identified. Ovary pair weights ranged from 0.38 to 2.45 kg and 2.92 to 12.02 kg for sexually immature and sexually mature whales, respectively. In sexually mature whales, corpora lutea (CLs) and/or large corpora albicantia (CAs) projected beyond ovary surfaces. CAs became increasingly less interruptive of the surface contour as they regressed, while remaining identifiable within transverse sections of the ovarian cortex. CLs formed large globular bodies, often with a central lumen, featuring golden parenchymas enfolded within radiating fibrous cords. CAs, sometimes vesicular, featured a dense fibrous core with outward fibrous projections through the former luteal tissue. CLs (never more than one per ovary pair) ranged from 6.7 to 15.0 cm in diameter in 13 whales. Fetuses were confirmed in nine of the 13 whales, with the associated CLs ranging from 8.3 to 15.0 cm in diameter. CLs from four whales where a fetus was not detected ranged from 6.7 to 10.6 cm in diameter. CA totals ranged from 0 to 22 for any single ovary, and from 1 to 41 for an ovary pair. CAs measured from 0.3 to 6.3 cm in diameter, and smaller corpora were more numerous, suggesting an accumulating record of ovulation. Neither the left nor the right ovary dominated in the production of corpora. Anat Rec, 299:769-797, 2016. © 2016 Wiley Periodicals, Inc.

A Horvitz–Thompson-type estimator is introduced to estimate total abundance of the Bering–Chukchi–Beaufort Seas population of bowhead whales using combined visual and acoustic location data. The estimator divides sightings counts by three correction factors that are themselves estimated from various portions of the data. The first correction models how detection probabilities depend on covariates like offshore distance and visibility. The second correction adjusts for availability using the acoustic location data to estimate a time-varying smooth function of the probability that animals pass within visual range of the observation stations. The third correction accounts for whales passing during periods when one or both sighting stations were temporarily closed down. We derive an asymptotically unbiased estimator of abundance incorporating all these components and a corresponding variance estimate. Correcting the count of 4011 observed whales yields a 2011 abundance estimate of 16,820 with a 95% confidence interval of (15,176, 18,643) and an estimated annual rate of population increase of 3.7% (2.9%, 4.6%). These results are indicative of very low conservation risk for this population under the current low levels of aboriginal hunting permitted by the International Whaling Commission. Although few other capture–recapture surveys will confront exactly the same set of challenges addressed here, many studies face one or more issues that could be resolved by adapting portions of our approach or relevant underlying concepts thereof. Moreover, the generic estimator we derive represents an improved way to handle random correction factors rather than assuming fixed values. Copyright © 2016 John Wiley & Sons, Ltd.

Two populations of beluga whales Delphinapterus leucas in the Pacific Arctic make seasonal migrations to regions characterized by diverse bathymetry and hydrography, yet there is limited information contrasting behavior and foraging across regions. We used satellite-linked timedepth recorders attached to 30 belugas from 1997 to 2012 to infer the depths at which belu- gas forage seasonally and regionally. We also examined the correspondence between patterns of beluga diving and the vertical distribution of a primary prey species, Arctic cod Boreogadus saida, within the western Beaufort Sea. A suite of regional diving metrics revealed that beluga dive behavior varied among regions and sometimes between populations. Estimates of occupancy time at depth, in addition to maximum and modal dive depths for 6 h periods, suggested that Eastern Chukchi Sea and Beaufort Sea belugas were regularly diving to the seafloor in shallow shelf regions. Along slope margins and in the deep Canada Basin (>3000 m), specific portions of the water column were more frequently targeted. The greatest maximum daily dive depths were >900 m in the Canada Basin. Arctic cod were most abundant at 200�300 m in the western Beaufort Sea, and beluga dives within the survey area also most frequently targeted these depths. These results are consistent with a hypothesis that Arctic cod are a primary prey item for Pacific Arctic belugas and suggest that foraging belugas dive to depths that maximize prey encounters. In the context of a rapidly transforming Arctic ecosystem increasingly exposed to anthropogenic activi- ties, our results quantify the ecological importance of key regions for these 2 populations.

Blubber and muscle were collected from male bowhead whales (n = 71) landed near Utqiaġvik (Barrow), Alaska, between 2006 and 2015 and analyzed for lipid content and concentrations of persistent organic pollutants (POPs) in order to determine levels and trends over the collection period. Collection year was a significant predictor of blubber concentrations for most classes of POPs, while for a few classes, animal length (proxy for age) was also a significant predictor. This is the first report on levels of PBDEs in bowhead whales; concentrations of these compounds are low (≤55 ng/g wet weight). Blubber concentrations were lower than those reported in samples collected between 1992 and 2000, and many POP classes in blubber declined significantly between 2006 and 2015. Concentrations of POPs in bowhead whale tissues, which are subsistence foods for Native Alaskan communities, appear to be declining at rates comparable with previously reported temporal trends in Arctic biota.

ECG was supported by a National Research Council-National Academy of Sciences Postdoctoral Fellowship. The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from aerial surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An aerial survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the aerial survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey. Postprint

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) were disposed directly into the Saguenay River of the St. Lawrence Estuary (SLE) by local aluminum smelters (Quebec, Canada) for 50 years (1926-1976). PAHs in the river sediments are likely etiologically related to gastrointestinal epithelial cancers observed in 7% of 156 mature (19-year old) adult beluga found dead along the shorelines. Because DNA adduct formation provides a critical link between exposure and cancer induction, and because PAH-DNA adducts are chemically stable, we hypothesized that SLE beluga intestine would contain PAH-DNA adducts. Using an antiserum specific for DNA modified with several carcinogenic PAHs, we stained sections of paraffin-embedded intestine from 51 SLE beluga (0-63 years), 4 Cook Inlet (CI) Alaska beluga (0-26 years), and 20 beluga (0-46 years) living in Arctic areas (Eastern Beaufort Sea, Eastern Chukchi Sea, Point Lay Alaska) and aquaria, all with low PAH contamination. Stained sections showed nuclear light-to-dark pink color indicating the presence of PAH-DNA adducts concentrated in intestinal crypt epithelial lining cells. Scoring of whole tissue sections revealed higher values for the 51 SLE beluga, compared with the 20 Arctic and aquarium beluga (P = 0.003). The H-scoring system, applied to coded individual photomicrographs, confirmed that SLE beluga and CI beluga had levels of intestinal PAH-DNA adducts significantly higher than Arctic and aquarium beluga (P = 0.003 and 0.02, respectively). Furthermore, high levels of intestinal PAH-DNA adducts in four SLE beluga with gastrointestinal cancers, considered as a group, support a link of causality between PAH exposure and intestinal cancer in SLE beluga. Environ. Mol. Mutagen. 60:29-41, 2019. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

With the increase of human activity and corresponding increase in anthropogenic sounds in marine waters of the Arctic, it is necessary to understand its effect on the hearing of marine wildlife. We have conducted a baseline study on the spiral ganglion and Rosenthal's canal of the cochlea in beluga whales (Delphinapterus leucas) as an initial assessment of auditory anatomy and health. We present morphometric data on the length of the cochlea, number of whorls, neuron densities along its length, Rosenthal's canal length, and cross-sectional area, and show some histological results. In belugas, Rosenthal's canal is not a cylinder of equal cross-sectional area, but its cross-section is greatest near the apex of the basal whorl. We found systematic variation in the numbers of neurons along the length of the spiral ganglion, indicating that neurons are not dispersed evenly in Rosenthal's canal. These results provide data on functionally important structural parameters of the beluga ear. We observed no signs of acoustic trauma in our sample of beluga whales.

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.

Mammals vary dramatically in lifespan, by at least two-orders of magnitude, but the molecular basis for this difference remains largely unknown. The bowhead whale Balaena mysticetus is the longest-lived mammal known, with an estimated maximal lifespan in excess of two hundred years. It is also one of the two largest animals and the most cold-adapted baleen whale species. Here, we report the first genome-wide gene expression analyses of the bowhead whale, based on the de novo assembly of its transcriptome. Bowhead whale or cetacean-specific changes in gene expression were identified in the liver, kidney and heart, and complemented with analyses of positively selected genes. Changes associated with altered insulin signaling and other gene expression patterns could help explain the remarkable longevity of bowhead whales as well as their adaptation to a lipid-rich diet. The data also reveal parallels in candidate longevity adaptations of the bowhead whale, naked mole rat and Brandt's bat. The bowhead whale transcriptome is a valuable resource for the study of this remarkable animal, including the evolution of longevity and its important correlates such as resistance to cancer and other diseases.