Pacific Walrus (Odobenus rosmarus divergens) Resource Selection in the Northern Bering Sea

The Pacific walrus is a large benthivore with an annual range extending across the continental shelves of the Bering and Chukchi Seas. We used a discrete choice model to estimate site selection by adult radio-tagged walruses relative to the availability of the caloric biomass of benthic infauna and sea ice concentration in a prominent walrus wintering area in the northern Bering Sea (St. Lawrence Island polynya) in 2006, 2008, and 2009. At least 60% of the total caloric biomass of dominant macroinfauna in the study area was composed of members of the bivalve families Nuculidae, Tellinidae, and Nuculanidae. Model estimates indicated walrus site selection was related most strongly to tellinid bivalve caloric biomass distribution and that walruses selected lower ice concentrations from the mostly high ice concentrations that were available to them (quartiles: 76%, 93%, and 99%). Areas with high average predicted walrus site selection generally coincided with areas of high organic carbon input identified in other studies. Projected decreases in sea ice in the St. Lawrence Island polynya and the potential for a concomitant decline of bivalves in the region could result in a northward shift in the wintering grounds of walruses in the northern Bering Sea.     

Migration of Walruses (Odobenus rosmarus) in the Svalbard and Franz Josef Land area

Thirty-four walruses ( Odobenus rosmarus ) were fitted with satellite transmitters (PTTs) from 1990 to 1993 in order to study the distribution of the population in the Svalbard area. Twenty-eight were caught at Svalbard and six at Franz Josef Land. All were males except one female caught at Franz Josef Land. At Svalbard, one walrus was caught on the west coast of Spitsbergen, while the others were caught at southern Edgeøya. All walruses were caught in the period from mid-July to early September. The PTTs provided information on location for periods ranging from 0 to 212 days. The results of the satellite trackings show that there is a migration of male walruses between most of the walrus areas at Svalbard and Franz Josef Land. In particular, it seems that migration of males from southern Edgeøya to Kvitøya, Viktoria Island, and Franz Josef Land is common. The walruses winter in the southern parts of Svalbard, as well as within the winter pack-ice of north-eastern Svalbard, which contains numerous open leads. The only walrus at Franz Josef Land that was followed to mid-winter stayed in the area and therefore supports the view that walruses also winter in that area. It is assumed that the majority of walruses at Svalbard are males from one common Svalbard-Franz Josef Land stock. The walrus in the Svalbard-Franz Josef Land area today belong to a recovering population. Their current distribution and behaviour may therefore differ from that found in Svalbard in former times.     

Faecal DNA amplification in Pacific walruses (Odobenus rosmarus divergens)

Dietary information is critical for assessing the population status of seals, sea lions and walruses—and is determined for most species of pinnipeds using non-invasive methods. However, diets of walruses continue to be described from the stomach contents of dead individuals. Our goal was to assess whether DNA could be extracted from the faeces of Pacific walruses (Odobenus rosmarus divergens) collected at haulout sites, and whether potential prey species or taxa could be amplified from that DNA. We extracted DNA from 70 faecal samples collected from ice pans in the Bering Sea during the spring of 2008 and 2009 (with between 4.6 and 308.9 ng/μl of DNA in every sample). We also extracted DNA from 12 potential prey species or taxa collected by bottom-grabs in 2009 to identify positive controls for primers and to test the ability of previously published taxon-specific and species-specific primers to correctly identify the prey using conventional PCR. We tested primers that successfully amplified DNA from the tissue of at least one potential prey species or taxon on all 70 walrus faecal samples. We found that two sets of primers successfully amplified many of the potential prey species or taxa using DNA from their tissue, and that one of these primer sets produced positive amplification in 4 of the 70 faecal samples. The band size that was produced for prey organisms and in the faecal samples was consistent with expectations, although prey identities were not verified with sequencing. Our pilot study demonstrates that DNA can be successfully extracted and amplified from walrus faeces, providing a stepping stone towards describing the diets of walruses from faecal DNA.     

Estimation of walrus populations on sea ice with infrared imagery and aerial photography

Population sizes of ice‐associated pinnipeds have often been estimated with visual or photographic aerial surveys, but these methods require relatively slow speeds and low altitudes, limiting the area they can cover. Recent developments in infrared imagery and its integration with digital photography could allow substantially larger areas to be surveyed and more accurate enumeration of individuals, thereby solving major problems with previous survey methods. We conducted a trial survey in April 2003 to estimate the number of Pacific walruses (Odobenus rosmarus divergens) hauled out on sea ice around St. Lawrence Island, Alaska. The survey used high altitude infrared imagery to detect groups of walruses on strip transects. Low altitude digital photography was used to determine the number of walruses in a sample of detected groups and calibrate the infrared imagery for estimating the total number of walruses. We propose a survey design incorporating this approach with satellite radio telemetry to estimate the proportion of the population in the water and additional low‐level flights to estimate the proportion of the hauled‐out population in groups too small to be detected in the infrared imagery. We believe that this approach offers the potential for obtaining reliable population estimates for walruses and other ice‐associated pinnipeds.     

The influence of ice conditions on terrestrial haulouts of the pacific walrus Odobenus rosmarus divergens Illiger, 1815 in the Gulf of Anadyr,Bering Sea

The boundaries of the area of appropriate depths for feeding by the Pacific walrus were determined. Based on the ice maps for the period of 1997–2011, the long-term dynamics of ice breakup and formation in the Gulf of Anadyr (Bering Sea) were analyzed. There was a tendency towards a reduction in the ice-cover period in the Gulf of Anadyr, especially during 2007–2011. In 2008, the number and duration of stay of walruses at terrestrial haulout sites on Meeskyn Spit Island and on Retkyn Spit continued to decrease. Walruses also used other haulouts located in the Gulf of Anadyr at Cape Gek and Cape Retkyn. The age and sex structure of the walrus herd changed: the proportions of adult males and young animals decreased, while the proportion of females with calves increased.     

Body size of male Atlantic walruses (Odobenus rosmarus rosmarus) from Svalbard

Morphometric data are given for 41 adult male Atlantic walruses ( Odobenus rosmarus rosmarus) immobilized at Svalbard. Total body weight ranged from 960 to 1450 kg. Standard body length ranged from 258 to 380 cm, while curvilinear tusk length ranged from 17 to 65 cm. Immobilized animals were selected for their large size. The sample is therefore biased towards larger animals. Based on regression equations developed for walruses caught in Greenland, the weights of Svalbard walruses were estimated from standard body length and axillary girth. Estimated weights ranged from 632 to 1883 kg. The present data suggest that Atlantic walruses at Svalbard can attain the same body size as Pacific ( O. r. divergens ) and Laptev walruses (O. r. laptevi).     

The number of walruses (Odobenus rosmarus) in Svalbard in summer

Walruses were on the verge of extinction in Svalbard prior to becoming totally protected in 1952. The present study attempts to determine the number of walruses in Svalbard in summer based on aerial, ground and boat surveys. In 1993, 741 walruses were observed, almost all of which were males. This population, which is shared with the neighbouring Russian archipelago Franz Joseph Land, is believed to consist of an equal number of females. We therefore conclude that the shared population consists of a minimum of about 1450 walruses older than 2 years and an unknown number of calves.     

Body growth in Atlantic walruses (Odobenus rosmarus rosmarus) from Greenland

Morphometric data were collected from 105 Atlantic walruses ( Odobenus rosmarus rosmarus ) in northwestern Greenland in the periods 1977–78 and 1989–91. Of these 21 walruses were subjected to a detailed study on body composition.
The asymptotic maximum standard body length of Atlantic walruses in NW Greenland was 269 cm for females and 314 cm for males. This is similar to Pacific walruses, but significantly longer than Atlantic walruses from Hudson Bay. Despite this, walruses from NW Greenland apparently do not attain the same total body mass as Pacific walruses ( O.r.divergens ).
The asymptotic maximum body weights for walruses in NW Greenland were estimated to be 720 kg for females and 1114 kg for males.
Total body surface area was proportional to the two-thirds power of total body weight.
The percentage proportion of blubber and viscera were both negatively correlated to body mass, while skin and muscles constituted a nearly fixed proportion. On average, blubber constituted 19% of total body mass of adult females, 15% of adult males and 24% of subadults of both genders. The average walrus consisted of 18% blubber, 12% skin, 12% viscera and 58% blood, muscle and skeleton. Muscles were estimated to constitute 44% of total body weight.
Allometric functions for weight of internal organs relative to body mass are presented.     

Haul-out and diving activity of male Atlantic walruses (Odobenus rosmarus rosmarus) in NE Greenland

During August-September 1989 and 1990, movements, haul out and dive activity of male Atlantic walruses ( Odobenus rosmarus rosmarus L.) were studied at a terrestrial haul-out site situated in an inshore foraging area in NE Greenland at 76± 30' N. Data were collected from direct observations of a group of about 50 males during August, including walruses that could be individually identified from natural markings, and from tracking of 8 adults equipped with satellite-linked radio transmitters during August-September. In both years, instrumented walruses hauled out for a total of 29.3% of the sampling time. In 1989, when ice floes were available for hauling out, the walruses spent 11% of the time on ice, whereas in 1990, when ice was absent from the study area, they only hauled out on land. Duration of haul-out periods, which did not differ between months or years, averaged 11 h (0.46 d) on ice (S.D. = 5.9, range: 1–29 h, n = 19 periods), and 38 h (1.6 d) on land (S.D. = 11.7, range: 13–64 h, n = 43). The walruses mainly hauled out during the afternoon and evening. Numbers hauling out on land during August were negatively correlated with wind direction, precipitation (rain) and wind-chill. In 1989, the duration of periods of absence from the terrestrial haul-out site (i.e. presumed foraging trips) averaged 206 h or 8.5 d (S.D. = 106.9, range: 48–412 h, n = 13), whereas, in 1990, such trips averaged only 81 h or 3.4 d (S.D. = 37.9, range: 24-156 h, n = 24), reflecting that walruses used the haul-out site more frequently when ice was absent. Direct observations of foraging walruses showed that they were submerged about 81% of the time.     

Proportion of higher trophic-level prey in the diet of Pacific walruses (Odobenus rosmarus divergens)

During nutritionally stressful situations, Pacific walruses (Odobenus rosmarus divergens) may switch from preying on benthic invertebrates to higher trophic-level prey (HTLP) (e.g., pinnipeds and/or seabirds). We applied a Bayesian mixing model to stable isotope (C and N) data from analyses of various tissues (tongue and lumbar muscle, skin, and liver) to quantify the proportional contribution of HTLP to walruses (n = 293 individuals). The mode contribution of HTLP to walrus diet was ~22 % (±10 %) based on muscle mixing models, which is consistent with results from contaminant studies of Atlantic walruses (Odobenus rosmarus rosmarus), but higher than estimates based on historical stomach content analyses of Pacific walruses. A broader range in the proportion of HTLP (0–60 %) shown by mixing models using stable isotope data from liver and skin of walruses indicated they pursue an opportunistic foraging strategy. Data from the HTLP-consuming walruses were comparable with our stable isotope data of a known “seal-eating” walrus. No significant difference was evident between the estimated contributions of HTLP to the diet of male versus female walruses (P > 0.01). This finding suggests that changes in diet base for walruses are not influenced by the sex of the predator.     

Levels of cadmium and mercury in the hair of Atlantic walruses (Odobenus rosmarus rosmarus) from Svalbard,Norway

Hair samples of 15 adult male Atlantic walruses (Odobenus rosmarus rosmarus) collected from anaesthetized individuals at Svalbard, Norway, were analysed for cadmium and total mercury. The mean level of cadmium was 0.860 ± 0.321 μg/g dry weight (median = 0.811, range = 0.349–1.51 μg/g dry weight) and the mean level of mercury was 0.235 ± 0.100 μg/g dry weight (median = 0.251, range = 0.121–0.424 μg/g dry weight). Levels of cadmium and mercury in hair of walruses from other areas are not known. Both cadmium and mercury levels in hair of walruses from Svalbard are relatively low compared to the levels found in the hair of other marine mammal species. It has been documented from a number of marine species, including marine mammals such as ringed seals and polar bears, that both cadmium and mercury levels at Svalbard are lower than in other areas. It is uncertain as to what degree levels in hair reflect levels in internal organs in walruses. In rare and highly endangered species or populations tissue samples can be difficult to collect. In walruses, it is possible to collect hair from anaesthetized individuals or at the haul-out sites during moult, to monitor heavy metal levels of the population. Accepted: 6 December 1998     

Antibodies to marine caliciviruses in the Pacific walrus (Odobenus rosmarus divergens Illiger)

Sera from 155 Pacific walruses (Odobenus rosmarus divergens Illiger), sampled in the Chukchi Sea during the summer of 1983, were tested for serum neutralizing (SN) antibodies to six marine calicivirus serotypes. Serotypes tested included San Miguel sea lion virus (SMSV) types 1, 5, 8, and 10, previously isolated from northern fur seals (Callorhinus ursinus Linné) in the Bering Sea; walrus calicivirus (WCV), previously isolated from walrus feces collected off sea ice in the Chukchi Sea; and Tillamook calicivirus (TCV), a bovine isolate from Oregon of suspected marine origin. No antibodies were found to SMSV-1, SMSV-10, or TCV. Antibodies to SMSV-5 were found in two animals (titers 1:20 and 1:160); antibodies to SMSV-8 were found in four animals (all 1:20); and antibodies to WCV were found in one animal (titer 1:40). Antibodies to WCV have been found in the Pacific walrus previously; however, this represents the first report of antibodies to any of the SMSV serotypes in this marine mammal.     

Regional walrus abundance estimate in the United States Chukchi Sea in autumn

Human activities (e.g., shipping, tourism, oil, gas development) have increased in the Chukchi Sea because of declining sea ice. The declining sea ice itself and these activities may affect Pacific walrus (Odobenus rosmarus divergens) abundance; however, previous walrus abundance estimates have been notably imprecise. When sea ice is absent from the eastern Chukchi Sea, walruses in waters of the United States usually rest together onshore at a single Alaska coastal haulout, where they can be surveyed more easily than when they rest on dispersed offshore ice floes. We estimated the number of walruses on land (herd size) at this haulout from 13 unoccupied aircraft system (UAS) surveys flown within a 10-day period in each of 2018 and 2019. We estimated population size of walruses using the haulout over the course of the surveys by combining herd size data with data from satellite-linked transmitters that indicated whether tagged walruses were in or out of water during each survey. Our estimates of the population size of walruses using the haulout during each year's survey period were similar to each other and more precise than historical walrus abundance estimates: posterior means (95% credibility intervals) were 166,000 (133,000–201,000) for 2018 and 189,000 (135,000–251,000) for 2019. Auxiliary observations support using these estimates to represent the size of the population using the eastern Chukchi Sea in autumn during the surveyed years. Our study site was the only substantial Chukchi Sea coastal haulout in the United States during the survey periods and study-specific tracking data (consistent with known distribution and movement patterns) indicated tagged walruses remained in eastern Chukchi waters during the survey periods. In addition, the imagery, telemetry, and analytical methods developed for this study advance the prospect for precise range-wide walrus population size estimates.     

Towards a Better Understanding of the Effects of UV on Atlantic Walruses,Odobenus rosmarus rosmarus: A Study Combining Histological Data with Local Ecological Knowledge

Walruses, Odobenus rosmarus, play a key role in the Arctic ecosystem, including northern Indigenous communities, which are reliant upon walruses for aspects of their diet and culture. However, walruses face varied environmental threats including rising sea-water temperatures and decreasing ice cover. An underappreciated threat may be the large amount of solar ultraviolet radiation (UV) that continues to reach the Arctic as a result of ozone loss. UV has been shown to negatively affect whales. Like whales, walrus skin is unprotected by fur, but in contrast, walruses spend long periods of time hauled-out on land. In this study, we combined the results of histological analyses of skin sections from five Atlantic walruses, Odobenus rosmarus rosmarus, collected in Nunavik (Northern Quebec, Canada) with qualitative data obtained through the interviews of 33 local walrus hunters and Inuit Elders. Histological analyses allowed us to explore UV-induced cellular lesions and interviews with experienced walrus hunters and Elders helped us to study the incidences and temporal changes of UV-induced gross lesions in walruses. At the microscopic scale, we detected a range of skin abnormalities consistent with UV damage. However, currently such UV effects do not seem to be widely observed at the whole-animal level (i.e., absence of skin blistering, erythema, eye cataract) by individuals interviewed. Although walruses may experience skin damage under normal everyday UV exposure, the long-term data from local walrus hunters and Inuit Elders did not report a relation between the increased sun radiation secondary to ozone loss and walrus health.     

Results and evaluation of a survey to estimate Pacific walrus population size, 20061

In spring 2006, we conducted a collaborative U.S.–Russia survey to estimate abundance of the Pacific walrus (Odobenus rosmarus divergens). The Bering Sea was partitioned into survey blocks, and a systematic random sample of transects within a subset of the blocks was surveyed with airborne thermal scanners using standard strip‐transect methodology. Counts of walruses in photographed groups were used to model the relation between thermal signatures and the number of walruses in groups, which was used to estimate the number of walruses in groups that were detected by the scanner but not photographed. We also modeled the probability of thermally detecting various‐sized walrus groups to estimate the number of walruses in groups undetected by the scanner. We used data from radio‐tagged walruses to adjust on‐ice estimates to account for walruses in the water during the survey. The estimated area of available habitat averaged 668,000 km² and the area of surveyed blocks was 318,204 km². The number of Pacific walruses within the surveyed area was estimated at 129,000 with 95% confidence limits of 55,000–507,000 individuals. Poor weather conditions precluded surveying in other areas; therefore, this value represents the number of Pacific walruses within about half of potential walrus habitat.     

Use of skin biopsies for assessing levels of organochlorines in walruses (Odobenus rosmarus)

Skin and blubber samples of ten adult male Pacific walruses (Odobenus rosmarus divergens) from Alaska were used to investigate the relationship between organochlorine (OC) levels in skin and blubber of individuals. For analyses we selected 11 components that were quantified in the blubber of all individuals: hexachlorocyclohexanes (αHCH and βHCH), the DDT (dichlorodiphenyltrichloroethane) metabolite p,p′DDE, oxychlordane, and 7 individual PCB congeners, 28, 99, 105, 118, 138, 153 and 180. The correlation between the levels in the two types of tissues was significant and the relation was isometric for all components. The regression coefficient between levels in blubber (dependent variable) and levels in skin (independent variable) was different from 1 for only four of the components. The mean levels in the two types of tissues were significantly different for 3 of the 11 chemical components (βHCH, oxychlordane, and PCB28). Although this analysis is based on only ten individuals, we propose that skin samples taken by biopsy darts can be used to monitor OC levels in walruses. In August 1993 skin biopsies were collected from 25 adult male Atlantic walruses (O. r. rosmarus) at haul-out sites in southeastern Svalbard in the Norwegian Arctic and from 28 walruses of different sex and age at haul-out sites at Franz Josef Land in the Russian Arctic. The mean levels of OCs were 2–10 times higher at Svalbard than at Franz Josef Land. The dominant OC component was PCB153 in both areas. A principal component analysis detected differences between areas in OC levels but not in patterns. Since the Franz Josef Land samples were mainly taken from females and young individuals and the Svalbard samples were taken largely from adult males, we believe the differences in tissue OC levels observed from these areas can be explained by differences in sex and age of the walrus sampled. Comparable organochlorine levels in skin samples from walruses from other areas are not available. However, compared to the corresponding OC levels found in walrus blubber in other areas, the OC levels from Svalbard and Franz Josef Land are higher. The high levels of OCs in walruses from Svalbard and Franz Josef Land may be a combined effect of high pollution level in the environment and seal-eating habits. In the present study we show that it is possible to use skin biopsies taken by a non-destructive method to assess OC levels in walruses. Accepted: 24 October 1999     

Population structure and gene flow of the Atlantic walrus (Odobenus rosmarus rosmarus) in the eastern Atlantic Arctic based on mitochondrial DNA and microsatellite variation

The population structure of the Atlantic walrus, Odobenus rosmarus rosmarus , was studied using 11 polymorphic microsatellites and restriction fragment length polymorphism detected in the NADH-dehydrogenase ND1, ND2 and ND3/4 segments in mtDNA. A total of 105 walrus samples were analysed from northwest (NW) Greenland, east (E) Greenland, Svalbard and Franz Joseph Land. Two of the 10 haplotypes detected in the four samples were diagnostic for the NW Greenland sample, which implied that the group of walruses in this area is evolutionary distinct from walruses in the other three areas. One individual sampled in E Greenland exhibited a Pacific haplotype, which proved a connection between the Pacific walrus and walruses in eastern Greenland. The Franz Joseph Land, Svalbard and E Greenland samples shared the most common haplotype, indicating very little differentiation at the mtDNA level. Gene flow ( Nm ) estimates among the four areas indicated a very restricted exchange of female genes between NW Greenland and the more eastern Atlantic Arctic samples, and a closer relationship between the three samples composing the eastern Atlantic Arctic. The genetic variation at 11 polymorphic microsatellite loci grouped individuals into three populations, NW Greenland, E Greenland and a common Franz Joseph Land–Svalbard population, which were connected by moderate gene flow.     

AERIAL CENSUS OF PACIFIC WALRUSES IN THE CHUKCHI SEA, 1985

The U.S. Fish and Wildlife Service conducted a survey of the walruses in the pack ice of the Chukchi Sea between 16 September and 2 October 1985, as part of a joint effort with the Soviet Union to estimate the size of the Pacific walrus population. American observers conducted censuses from two aircraft along randomly selected north–south lines over the pack ice. The observers counted walruses within a constant viewing angle that corresponded to a total strip width of 1.38 km at an altitude of 152 m.
In nine days of flying, 15,312 walruses were observed, of which 10,140 were on 5,764 km² of census strips. Few walruses were observed east of 161°W longitude or west of 170°W longitude, hence the census effort was stratified. Walrus concentrations between 161° and 170° shifted slightly westward during the 2-wk duration of the censuses. The differences among days in observed walrus density were due to changes in the numbers of walruses on the ice within 37 km of the ice edge. The number of observable walruses in pack ice of the eastern Chukchi Sea was estimated to be 62,177 (SD = 19,480), based on censuses conducted on 29 and 30 September and 1 October. At that time there were also at least 15,238 in Bristol Bay, Bering Sea. The Soviets counted 39,572 on the shores of the western Chukchi and Bering seas and estimated 115,531 in pack ice of the western Chukchi Sea. Summing U.S. and Soviet estimates, the total population of Pacific walruses in 1985 was 232,518. This number was comparable with earlier estimates from censuses conducted jointly by the U.S. and the Soviets. However, information on fraction hauled out, segregation, and movements is needed for more precise estimates.     

Estimating Age Ratios and Size of Pacific Walrus Herds on Coastal Haulouts using Video Imaging

During Arctic summers, sea ice provides resting habitat for Pacific walruses as it drifts over foraging areas in the eastern Chukchi Sea. Climate-driven reductions in sea ice have recently created ice-free conditions in the Chukchi Sea by late summer causing walruses to rest at coastal haulouts along the Chukotka and Alaska coasts, which provides an opportunity to study walruses at relatively accessible locations. Walrus age can be determined from the ratio of tusk length to snout dimensions. We evaluated use of images obtained from a gyro-stabilized video system mounted on a helicopter flying at high altitudes (to avoid disturbance) to classify the sex and age of walruses hauled out on Alaska beaches in 2010–2011. We were able to classify 95% of randomly selected individuals to either an 8- or 3-category age class, and we found measurement-based age classifications were more repeatable than visual classifications when using images presenting the correct head profile. Herd density at coastal haulouts averaged 0.88 walruses/m² (std. err. = 0.02), herd size ranged from 8,300 to 19,400 (CV 0.03–0.06) and we documented ∼30,000 animals along ∼1 km of beach in 2011. Within the herds, dependent walruses (0–2 yr-olds) tended to be located closer to water, and this tendency became more pronounced as the herd spent more time on the beach. Therefore, unbiased estimation of herd age-ratios will require a sampling design that allows for spatial and temporal structuring. In addition, randomly sampling walruses available at the edge of the herd for other purposes (e.g., tagging, biopsying) will not sample walruses with an age structure representative of the herd. Sea ice losses are projected to continue, and population age structure data collected with aerial videography at coastal haulouts may provide demographic information vital to ongoing efforts to understand effects of climate change on this species.     

Subtidal populations of the blue mussel <Emphasis Type="Italic">Mytilus edulis</Emphasis> as key determinants of waterfowl flocks in the southeastern Barents Sea

Ornithological surveys conducted over the Pechora Sea (the southeastern part of the Barents Sea) in the 1990 s revealed huge non-nesting flocks of marine ducks, the largest in the European North. Especially dense waterfowl aggregations are constantly observed at the shallows near Dolgij Island during molting period and migration to wintering places. All the marine ducks flocking there are specialized benthos feeders predominantly consuming mussels Mytilus edulis. At the same time, numerous previous benthic studies in the Pechora Sea did not reveal mussels near Dolgij Island where benthic biomass was somewhat lower than in the adjacent areas (Denisenko in Mar Ecol Prog Ser 258:109–123. 2003) which left the food source for these abundant bird flocks enigmatic. In the course of an expedition in summer 2007 we found subtidal populations of M. edulis in shallows to the southwest of Dolgij Island. These populations were confined to a coastal zone and were characterized by a highly disjunct distribution with the biomass reaching up to 4 kg m⁻². We describe these subtidal populations as well as an intertidal mussel population on the western shore of Dolgij Island.