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Spotted seal
Spotted seal mother and pup in the Bering Sea
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Phocidae
Genus: Phoca
Species:
P. largha
Binomial name
Phoca largha
Pallas, 1811
Spotted seal distribution

The spotted seal (Phoca largha),[2] also known as the larga seal or largha seal, is an earless seal (or true seal, Phocidae). It inhabits ice floes and waters of the north Pacific Ocean and adjacent seas. It is primarily found along the continental shelf of the Beaufort, Chukchi, Bering and Okhotsk Seas[3] and south to the northern Yellow Sea and it migrates south as far as northern Huanghai and the western Sea of Japan. It is also found in Alaska from the southeastern Bristol Bay to Demarcation Point during the ice-free seasons of summer and autumn when spotted seals mate and have pups. Smaller numbers are found in the Beaufort Sea.[4] It is sometimes mistaken for the harbor seal to which it is closely related and spotted seals and harbor seals often mingle together in areas where their habitats overlap.[5]

The reduction in arctic ice floes due to global warming led to concerns that the spotted seal was threatened with extinction. Studies were conducted on its population numbers, with the conclusion, as of 15 October 2009, that the spotted seal population in Alaskan waters is not currently to be listed as endangered by NOAA.[6]

Etymology

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The scientific name originated in the Greek word for seal, phoce, and larga, the term used by the Siberian Tungus people for this seal. The English common name comes from this seal's characteristic dark, irregularly shaped spots. Alaskan Eskimo names include issuriq (Central Alaskan Yup'ik language), gazigyaq in St. Lawrence Island Yupik, and qasigiaq in Inupiaq.[4]

Description

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Spotted seal in the Bering Sea

The spotted seal is of the family, Phocidae, or "true seals". Compared to other true seals, they are intermediate in size, with mature adults of both sexes generally weighing between 82–109 kg (180–240 lb) and measuring 150–210 cm (59–83 in), roughly the same size as a harbor seal or ribbon seal. The head of a spotted seal is round, with a narrow snout resembling that of a dog.[4]

The spotted seal has a relatively small body and short flippers extending behind the body that provide thrust, while the small flippers in front act as rudders. The dense fur varies in color from silver to gray and white and is characterized by dark, irregular spots against the lighter background and covering the entire body. Males and females differ little in size or shape. In places where their habitat overlaps with that of the harbor seal, they can be confused with them, as in Bristol Bay, Alaska. Like harbor seals, spotted seals have 34 teeth.[4][7]

Distribution and habitat

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Spotted seal showing narrow snout like that of a dog[4]

Spotted seals are inhabitants of arctic or sub-arctic waters, often in the outer areas of ice floes during the breeding season. They tend not to live within dense drift ice. In the summer months they live in the open ocean or on nearby shores.[7]

Spotted seals are separated into three populations. The Bering Sea population includes approximately 100,000 in the western Bering Sea near Kamchatka, in the Gulf of Anadyr in Russia, and in the eastern Bering Sea in Alaskan waters (the only population in the US). A second population of about 100,000 seals breeds in the Sea of Japan and the Sea of Okhotsk. A third population of about 3,300 seals is to the south in Liaodong Bay, China and Peter the Great Bay, Russia.[7] There is also a smaller population of 300 spotted seals living in waters off Baekryeong Island located far north of the west coast of South Korea.

Behavior and reproduction

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Spotted seals are relatively shy and are difficult for humans to approach. They can be solitary in general but are gregarious and form large groups during pupping and molting seasons when they haul out on ice floes or, if lacking ice, on land. The numerically largest groups in Alaska are at Kasegaluk Lagoon in the Chukchi Sea, near Cape Espenburg in Kotzebue Sound, and in Kuskokwim Bay on sandbars and shoals, where several thousand may collect.[4]

Sexual maturity is attained around the age of four. January to mid-April is the breeding season. Pup births peak in mid-March. Spotted seals are believed annually monogamous, and during breeding season, they form "families" made up of a male, female, and their pup, born after a 10-month gestation period. Average birth size is 100 cm (39 in) and 12 kg (26 lb).[8] Pups are weaned six weeks later. The maximum lifespan of the spotted seal is 35 years with few living beyond 25.[7][8]

Spotted seals dive to depths up to 300 m (980 ft) while feeding on a variety of ocean prey. Juveniles eat primarily krill and small crustaceans while adults eat a variety of fish including herring, Arctic cod, Pacific cod, pollock, and capelin, as well as mollusks and crustaceans.[4][9] They do not seem to vocalize a lot, although not much is known about their vocalizations. They appear to vocalize more while in molting groups. When approached in these groups, they make various sounds such as growls, barks, moans, and roars.[4]

Based on satellite tracking conducted on Yellow Sea population, it was revealed that seals migrate more than 3,300 km (2,100 mi).[10]

Conservation status

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On 28 March 2008, the U.S. National Oceanic and Atmospheric Administration (NOAA) initiated a status review[11] under the Endangered Species Act (ESA) to determine if listing this ice seal species under the ESA was warranted. After an 18-month review of the status of the spotted seal, NOAA announced on 15 October 2009 that two of the three spotted seal populations, together numbering 200,000 seals in or adjacent to Alaska, are not in danger of becoming extinct, nor are they likely to become so in the "foreseeable future",[6] even though global warming has caused a loss in arctic ice mass. The announcement stated: "We do not predict the expected fluctuations in sea ice will affect them enough to warrant listing at this time."[12]

In China, the spotted seal was under class-II national protection in the past,[citation needed] but the protection level was raised to class-I in 2021.[13] The main threats to the species in China are global warming, marine traffic, industry noise, ocean pollution, and poaching for aquarium exhibition.[14]
In South Korea, spotted seals have been designated Natural Monument No. 331[15] and second-class endangered species.[16] An environmental activist group Green Korea United is currently working closely with local Chinese government to stop the seals from being poached by Chinese fishermen.[17]

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Spotted seal

View on Grokipedia
from Grokipedia
The spotted seal (Phoca largha) is a of true seal in the Phocidae, native to the seasonally ice-covered waters of the northern , where it relies on pack ice for breeding, molting, and resting. Adults typically measure 1.5 to 1.8 meters in length and weigh 70 to 120 kilograms, with females generally larger than males, and possess a pale gray coat adorned with irregular dark spots that provide on ice. This pagophilic species forages primarily on fish such as and , as well as crustaceans and mollusks, in coastal and pelagic zones over continental shelves. Spotted seals range across the Bering, Chukchi, , and East Siberian Seas, migrating northward in summer to follow retreating ice and retreating southward in winter, with some individuals occasionally straying to the northern or even . Breeding occurs in late winter to early spring on fast ice, where females give birth to a single pup after a period of about 11 months, including delayed implantation; pups are nursed for 2 to 4 weeks before and shedding their natal white . is reached at 3 to 5 years, and the species exhibits seasonal during reproductive aggregations on ice. The global population exceeds 500,000 individuals, though precise trends remain uncertain due to limited surveys, and the is classified as Least Concern by the , reflecting its relatively stable status despite regional declines. Primary threats include loss from diminishing linked to warming, incidental entanglement in fishing gear, and historical subsistence hunting, particularly in and , though populations appear resilient to moderate exploitation levels. In the United States, the southern distinct population segment was considered for Endangered Species Act listing but not designated as threatened overall, underscoring the ' broad adaptability amid environmental pressures.

Taxonomy and Nomenclature

Scientific Classification

The spotted seal (Phoca largha Pallas, 1811) is a true seal in the family Phocidae, distinguished taxonomically from harbor seals (Phoca vitulina) by morphological and genetic differences, including distinct spot patterns and breeding behaviors.
Taxonomic RankName
KingdomAnimalia
Phylum
ClassMammalia
Order
FamilyPhocidae
Genus
SpeciesP. largha
This classification reflects its placement among the earless seals (Phocidae), within the suborder Pinnipedia of carnivorans adapted to marine life. The is assessed as Least Concern by the , based on population estimates exceeding 400,000 individuals across its range, though regional subpopulations face threats from habitat loss.

Etymology and Common Names

The binomial name Phoca largha was first described by in 1811. The genus name originates from the phōkē (φώκη), denoting a seal. The specific epithet largha derives from the Russian vernacular "larga," which stems from the of in eastern , reflecting early regional nomenclature for the . In English, the species is most commonly called the spotted seal, a designation based on its characteristic pelage featuring a light gray or yellowish background marked by irregular dark spots and patches. Alternative English names include larga seal and largha seal, mirroring the Russian term and emphasizing its historical use in the North Pacific. Among Alaskan Native communities, indigenous names vary by , such as qasigiaq in Inupiaq, gazigyaq in St. Lawrence Island , issuriq in , and issuri in Central , highlighting localized cultural recognition of the animal.

Physical Characteristics

Morphology and Size

The spotted seal (Phoca largha) possesses a streamlined body typical of phocid seals, adapted for efficient swimming and in cold marine environments, featuring a thick layer beneath the skin for insulation, , and energy storage. The head is small and rounded with a narrow, cat-like , large eyes set wide apart to facilitate during dives, and no external ear pinnae; auditory openings are minute and inconspicuous. Nostrils open forward and seal tightly during submersion to prevent water ingress. Foreflippers are short, extending about halfway down the body, with five digits bearing short hair and claws primarily on the first two for gripping ice or substrate during haul-outs. Hindflippers are longer, providing primary propulsion in water via motions, with the first digit longest and clawed, and fixed rigidly backward on land; both flipper sets lack the flexibility of otariid seals. A short, hair-covered aids minor steering. Adults exhibit slight , with males larger than females. Males measure 1.5–2.1 m in length and weigh 85–150 kg, while females range from 1.4–1.7 m and 65–115 kg. Comparable data indicate adult lengths up to 1.7 m for males and 1.6 m for females, with weights of 82–123 kg. NOAA assessments report average adult lengths of approximately 1.5–1.6 m and weights of 63–113 kg, noting overall similarity in appearance between sexes despite size differences. Newborn pups are born on with a dense white coat for , measuring 77–92 cm in length and weighing 7–12 kg; this coat is shed within 2–4 weeks, revealing the spotted pelage. Juveniles grow rapidly, reaching subadult sizes by the first year through nursing on high-fat milk.

Coloration and Distinctive Features

Adult spotted seals possess a pelage characterized by a silvery-gray to light gray base color, overlaid with dense, irregular dark spots ranging from dark gray to black across the entire body. These spots, typically 1-2 cm in diameter and oval-shaped, are more concentrated on the dorsal mantle, which appears darker, while the ventral side remains lighter. The dense provides in icy environments, with variations in background tone from silver to tan observed among individuals. Newborn pups are covered in a thick, woolly lanugo for insulation, which is molted after 2-4 weeks to reveal a juvenile of gray- with emerging dark spots. Juveniles may exhibit a temporary dark dorsal stripe that fades with age. This spotted pattern distinguishes Phoca largha from congeners like the (Pusa hispida), which features light rings on a dark background, or the (Phoca vitulina), which has less uniform spotting. The pelage's irregular spots, sometimes faintly encircled, enhance against predators in variable conditions.

Geographic Distribution and Habitat

Current Range

The spotted seal (Phoca largha) occupies continental shelf habitats (<200 m depth) across the northern Pacific Ocean, primarily in the Beaufort, Chukchi, Bering, Okhotsk, and southeastern East Siberian Seas, with vagrant occurrences south to the western Sea of Japan and northern Yellow Sea. Seasonal migrations define much of their range dynamics: individuals move southward through the Bering Strait in October, overwintering along the ice edges of the Bering and Okhotsk Seas where breeding occurs on pack ice, before dispersing northward in summer to coastal haul-out sites in the Chukchi and Beaufort Seas up to approximately 69–72°N. NOAA Fisheries delineates three distinct population segments (DPSs) based on breeding areas: the Bering DPS (encompassing U.S. waters of the Bering, Chukchi, and Beaufort Seas), the Okhotsk DPS, and the Southern DPS (south of 45°N, including the Yellow Sea and Japan). Abundance estimates for the U.S. Bering Sea portion indicate approximately 461,625 individuals as of the 2012 survey, reflecting the core of the Bering DPS range.

Habitat Requirements and Adaptations

Spotted seals depend on seasonal sea ice in the northern for critical life stages, primarily from late fall through spring, when they haul out on ice floes for resting, whelping, nursing, breeding, and molting. Sea ice functions as a protective platform against terrestrial predators and offers a stable, dry surface essential for pup survival and adult energy conservation during fasting periods associated with reproduction and molt. They select habitats featuring broken pack ice and thin floes near the ice front or marginal ice zone, facilitating access to open water for foraging and maintenance of breathing holes while avoiding dense, compacted ice that hinders mobility. During summer and early fall, after sea ice retreats, spotted seals migrate to coastal regions and utilize terrestrial haul-out sites including mudflats, sand or gravel beaches, and rocky shores, particularly near river mouths and estuaries. This behavioral flexibility reduces their reliance on ice relative to more ice-obligate phocids, allowing persistence in ice-free periods over continental shelves with depths typically under 200 meters where prey is abundant. Key adaptations to these variable ice and open-water habitats include a thick blubber layer, averaging 4.5 to 5.1 cm in adults during peak condition, serving as the primary insulator to minimize heat loss in subzero air and cold seawater. Behaviorally, some populations in enclosed bays employ terrestrial sites for whelping, with pups entering water before weaning, and individuals can traverse up to 10 km over fast ice to access polynyas or leads. These traits enable efficient thermoregulation and habitat opportunism amid seasonal environmental shifts.

Ecology and Foraging

Diet and Prey Species

Spotted seals (Phoca largha) are opportunistic generalist predators whose diet consists predominantly of fish, supplemented by crustaceans and cephalopods, with composition varying by region, season, age, and prey availability. Fish typically comprise the majority of intake, including species from families such as Gadidae (cod-like fishes); key examples include Arctic cod (Boreogadus saida), walleye pollock (Gadus chalcogrammus), saffron cod (Eleginus gracilis), (Clupea pallasii), capelin (Mallotus villosus), and sand lance. Crustaceans such as shrimp and crabs, along with cephalopods like squid and octopus, form secondary prey, often more prominent in winter or for younger seals. Regional differences are pronounced; in the Bering and Chukchi Seas, Arctic cod and shrimp dominate, whereas walleye pollock and saffron cod prevail in other Pacific Arctic areas. In the Sea of Okhotsk, Alaska pollock, greenling (Hexagrammidae spp.), and rockfish (Sebastes spp.) are primary targets, reflecting benthic and mid-water foraging. Seasonal shifts occur, with fish consumption peaking in summer and crustaceans increasing in winter, as evidenced by stomach content analyses. Spring diets in the Bering Sea further highlight subregional variation based on examinations of over 500 seals in Soviet studies (110 with food remains) and 51 in American studies (31 with remains): sand lance predominates in Karaginskii Gulf alongside herring and octopus; Arctic cod leads in Anadyr Gulf and northern Bering Sea, with capelin secondary; pollock is major in central areas with eelpout; and capelin heads southeastern samples, followed by pollock and herring. Northern Bering Sea samples yielded 14 prey species across 12 seals, compared to 8 species in 14 southeastern seals, underscoring localized diversity. Newly weaned pups favor small crustaceans, while adults pursue larger fish and invertebrates, enabling adaptation to both pelagic and benthic habitats via dives exceeding 300 m.

Predation and Mortality Factors

Spotted seals (Phoca largha) are preyed upon by a range of marine mammals, sharks, and terrestrial carnivores, with predation pressure varying by habitat, season, and life stage. Primary predators include killer whales (Orcinus orca), (Ursus maritimus), and walruses (Odobenus rosmarus), which encounter seals on sea ice or in coastal areas. Other documented predators encompass sleeper sharks, (Eumetopias jubatus), brown bears (Ursus arctos), wolves (Canis lupus), and arctic foxes (Vulpes lagopus). Pups, which are born on fast ice or haul-out sites, face heightened risk from avian predators such as eagles (Haliaeetus spp.), ravens (Corvus corax), and gulls (Larus spp.), as well as foxes; adult seals are more frequently targeted by large-bodied marine predators like killer whales during open-water periods. Spotted seals mitigate predation by selecting relatively inaccessible breeding and haul-out sites, such as offshore rocks or stable ice edges, though shifting sea-ice dynamics may increase exposure to killer whales as reduced ice cover allows greater access to coastal foraging grounds. Non-predatory mortality factors include infectious diseases, parasitic infections, nutritional deficits, and trauma from environmental hazards. Strandings often result from undetermined causes, but documented contributors involve harmful algal blooms, vessel strikes, and non-anthropogenic injuries, with pups showing higher rates of starvation and infectious etiologies in related phocid species. Unusual mortality events, such as the deaths of nearly 300 ice seals (including ) along Alaska's coasts from June 2018 to September 2019, prompted investigations into factors like biotoxins, pathogens, and physical trauma, but no definitive cause was identified despite ruling out sonar, seismic activity, and radiation. Declining sea ice may exacerbate mortality through increased energetic costs for foraging and thermoregulation, indirectly heightening susceptibility to starvation and predation.

Behavior and Physiology

Social and Movement Patterns


Spotted seals exhibit predominantly solitary behavior outside of breeding and molting periods, though they aggregate in large groups during haul-outs on ice or land. These haul-outs occur from late fall to early summer on ice floes and shift to terrestrial sites during warmer months, with group sizes sometimes exceeding 1,000 individuals. During the breeding season, they form distinctive family triads consisting of an adult female, an adult male, and a pup, which is atypical among phocid seals. These triads facilitate pup protection and mating, with vocalizations employed underwater for territorial defense and mate attraction. Movement patterns of spotted seals are characterized by seasonal migrations tied to ice availability and foraging opportunities. In the Bering and Chukchi Seas, satellite-tagged individuals display frequent east-west foraging excursions during open-water periods, with limited north-south transitions between seas, and often rest on shorelines. Southward migrations commence in mid-October, aligning with the retreat of sea ice, while spring movements northward follow breeding in southern latitudes. Juveniles from Russian breeding sites, such as Peter the Great Bay, migrate eastward and northward along continental coasts at average daily speeds of 70 to 135 kilometers. Diving behavior emphasizes near-bottom depths, with resident movements influenced by benthic conditions in the Pacific Arctic. In western Pacific populations, such as those utilizing the Bohai Sea for winter breeding, post-breeding migrations extend southward before resuming northward foraging. Haul-out patterns vary diurnally and seasonally, peaking during molting when seals expend less energy in water to conserve heat.

Sensory and Physiological Adaptations

Spotted seals (Phoca largha) possess amphibious hearing capabilities that facilitate communication and navigation in both aerial and aquatic environments, with underwater audiograms indicating auditory sensitivity from below 100 Hz to above 70 kHz and peak sensitivity between 10 and 30 kHz. In air, their hearing spans approximately four octaves, exhibiting sensitivity profiles akin to terrestrial carnivores such as cats, which supports vocal interactions during breeding and haul-out periods. These seals produce diverse underwater vocalizations, including low-frequency drums, growls, and knocks with dominant energy below 1 kHz, enabling territorial defense and mate attraction in noisy ice-covered habitats. Tactile sensitivity is enhanced by specialized mystacial vibrissae, or whiskers, which feature a three-dimensional wavy geometry that reduces self-generated flow noise and improves detection of hydrodynamic wakes from prey, allowing precise tracking over distances of several body lengths. Vision contributes to a sensory hierarchy for under-ice navigation, prioritized after audition but ahead of vibrissal touch, with seals demonstrating proficiency in locating breathing holes under experimental conditions simulating low visibility. Olfactory cues play a supplementary role in such tasks, though empirical data on spotted seal olfaction remains limited compared to auditory and tactile modalities. Physiologically, spotted seals maintain thermal homeostasis through a thick blubber layer that minimizes conductive heat loss in sub-zero waters, complemented by peripheral vasoconstriction and countercurrent heat exchange in flippers and tail to preserve core temperatures around 37-38°C. During molting, their resting metabolic rate elevates with increasing water temperature, reflecting active behavioral strategies like reduced activity in warmer conditions to counter elevated heat production from hair regrowth, unlike conspecific Arctic seals such as where rates decline. Diving physiology aligns with phocid adaptations, including elevated myoglobin concentrations in muscles for oxygen storage and dive-induced bradycardia to extend aerobic submergence, supporting foraging bouts typically lasting 3-5 minutes at depths up to several hundred meters.

Reproduction and Life History

Mating and Breeding Behaviors

Spotted seals breed primarily on sea ice during a season spanning January to mid-April, with peak pupping occurring in mid-March across their range in the , , and other northern seas. In some coastal regions, such as Peter the Great Bay, breeding shifts to land haul-out sites on small islands, facilitated by stable substrates amid variable ice conditions. The species displays an annual monogamous mating system unique among ice-breeding phocids, where males form pairs with females approximately 10 days prior to pupping. These pairs typically consist of the female, her current mate, and the pup from the previous season's mating, with the adult male defending the group against intruders. Mating occurs underwater shortly after the female gives birth, following a postpartum estrus, and involves male courtship behaviors such as vocalizations and synchronized dive displays observed in captive studies. Females nurse pups for about one month on the ice or haul-out, during which the pair remains together until weaning, after which the female mates and the cycle repeats annually. Sexual maturity is reached by nearly all individuals by age 5, enabling participation in this breeding pattern. This system contrasts with polygynous behaviors in related species, emphasizing prolonged pair bonding for pup protection amid predation risks on breeding grounds.

Pup Development and Growth Rates

Spotted seal pups (Phoca largha) are born on seasonal pack ice in the Bering and Okhotsk Seas during late March to early April, typically weighing 6.8 to 11.8 kg (15 to 26 pounds) at birth and possessing a white natal lanugo coat for camouflage and thermoregulation. This coat is shed around the time of weaning, which occurs after a nursing period of 3 to 6 weeks. During lactation, mothers provide high-fat milk that facilitates rapid pup growth, with pups remaining on the ice and dependent on maternal care until weaning. Studies of both captive and wild pups indicate comparable growth trajectories, with mean daily mass gains supporting the development of blubber reserves essential for thermoregulation and fasting post-weaning. By early May, pups reach average standard lengths of approximately 90 to 97 cm, reflecting substantial linear growth during the initial weeks. At weaning, pups enter the water to forage independently, undergoing a period of nutritional stress as they develop swimming, diving, and hunting skills; this transition prepares them for solitary life, though initial mass loss may occur before sustained foraging success. Growth rates slow post-weaning compared to lactation, with overall pup lengths increasing to around 160 cm by the end of the first year as asymptotic adult size is approached. Empirical data from Alaska collections across decades show consistent early growth patterns, though inter-annual variations in ice conditions may influence developmental timing.

Population Dynamics

The Bering Sea stock of spotted seals (Phoca largha), encompassing the primary portion of the global population, lacks precise range-wide abundance estimates due to challenges in surveying expansive ice habitats and accounting for availability bias. A minimum population estimate of 423,237 individuals was derived from aerial surveys conducted in 2012 across the Bering and Chukchi Seas, incorporating correction factors for seals at sea or unavailable for detection. Analysis of a subsample from the U.S. sector of the Bering Sea during the same 2012 survey produced an abundance estimate of 461,625 spotted seals (95% CI not specified in primary data summaries). Crude extrapolations from historical literature place the worldwide total above 500,000 individuals, though these figures predate modern systematic surveys and do not differentiate subpopulations reliably. Reliable trend data for the Bering Sea stock remain unavailable, as no repeated large-scale surveys have enabled statistical assessment of changes over time, and historical counts were inconsistent in methodology. Localized increases have been documented, such as a doubling of combined harbor and spotted seal numbers at Bering and Medny Islands since the 1980s, attributed to reduced harvesting pressures. In contrast, subpopulations in peripheral areas like the southern Sea of Okhotsk show lower abundances, with aerial counts estimating 13,653 individuals (95% CI: 6,167–30,252) in March surveys of limited ice fields, and no evident upward trajectory. Recent syntheses of Pacific Arctic ice seals, including spotted seals, characterize populations as large and healthy as of 2024, without indicators of broad decline.

Genetic Variation and Subpopulations

The spotted seal (Phoca largha) displays moderate genetic diversity in mitochondrial DNA (mtDNA), with studies of the control region identifying up to 49 haplotypes across sampled populations, many of which are unique to individuals or restricted to specific sampling locations. Analysis of mtDNA cytochrome b sequences reveals high genetic variance within populations (97.3%), substantially exceeding variance among populations (2.7%), indicative of ongoing gene flow across breeding areas. Recent assessments in the Liaodong Gulf, China, report haplotype diversity (h) of 0.92 and nucleotide diversity (π) of 0.014, reflecting population expansion between 2005 and 2020 following conservation efforts that mitigated historical declines. In contrast, nuclear microsatellite loci exhibit low variation, with observed heterozygosity typically below 0.5 and evidence of recent bottlenecks reducing allelic richness, likely due to anthropogenic pressures such as historical harvesting and habitat loss in isolated breeding grounds. Genome-wide sequencing estimates the P. largha genome size at approximately 2.4–2.5 Gb, with preliminary assemblies identifying sex-specific features but limited insights into overall polymorphism levels pending broader sampling. These patterns align with phylogeographic signals of post-glacial recolonization from refugia, where mtDNA retains higher diversity from maternal lineages while nuclear markers reflect effective population size contractions. Population genetic structure appears weak overall, with no significant differentiation detected in mtDNA sequences from seals along the Hokkaido coast, Japan, supporting connectivity via dispersal from major breeding concentrations in the Sea of Okhotsk. However, some evidence points to subtle substructuring, including two distinct mtDNA lineages and 17 haplotypes in samples from pupping grounds in the western North Pacific, with genetic divergence (F_ST > 0.1) between groups using the same breeding sites but different haul-out areas, potentially driven by fine-scale or local to ice conditions. In the , mtDNA analyses indicate isolation in the Liaodong Bay subpopulation, with lower diversity historically but recent recovery, though ongoing from northern stocks remains plausible. Subpopulations are primarily defined by breeding distributions rather than strong genetic barriers: the stock, Okhotsk Sea concentration, and peripheral East Asian groups (e.g., Liaodong Bay and ). Genetic data do not support full , as low inter-population divergence (F_ST < 0.05 in most mtDNA surveys) implies demographic exchange via migratory routes, yet localized bottlenecks in southern extents warrant subpopulation management to preserve adaptive potential against climate-driven ice loss. Contradictory findings across studies may stem from sampling biases or marker specificity, underscoring the need for integrated genomic approaches to resolve structure.

Human Interactions

Historical and Subsistence Use

Indigenous peoples inhabiting the Bering and Chukchi Seas, including Alaska Natives such as Yup'ik and Iñupiaq communities and Chukchi hunters in Russia, have traditionally harvested (Phoca largha) as a key subsistence resource for millennia, relying on them for food, fuel, and materials. The meat provides a primary protein source, blubber is rendered for oil used in cooking, lighting, and heating, and hides are processed into clothing items like boots, mittens, and slippers, as well as boat covers for kayaks. In the Norton Sound-Bering Strait region of Alaska, hunters target spotted seals primarily in late summer and fall using boats, with occasional spring hunts, valuing their meat for tenderness—particularly younger seals—and skins for crafts. Historical subsistence takes by Alaska Natives have been documented through sampling efforts by the Alaska Department of Fish and Game from coastal villages spanning Hooper Bay in the Bering Sea to Kaktovik in the , beginning in 1963 and continuing through 2008, with major data collection periods from 1963–1979 and 1998–2008. In the 1996–1997 hunting season across six communities in the Norton Sound-Bering Strait region (Brevig Mission, Gambell, Golovin, Savoonga, Shaktoolik, and Stebbins), an estimated 1,223 spotted seals were taken, with 1,028 harvested successfully and 195 struck but lost, peaking in September–October. Annual subsistence harvest by Alaska Natives is estimated at 5,000–6,000 individuals, remaining moderately low and stable without significant increases anticipated. Russian indigenous groups, including Chukchi marine mammal hunters, incorporate spotted seals into traditional practices alongside other pinnipeds, though specific harvest levels are less quantified; commercial Russian takes, which began in 1961 at around 2,500 annually, supplemented native subsistence but declined after 1990. These subsistence activities reflect consistent local knowledge of seal behavior and seasonal availability, with no reported major shifts in hunting patterns or locations over decades.

Commercial Exploitation and Bycatch

Commercial exploitation of the spotted seal (Phoca largha) has primarily targeted its pelt, meat, and blubber in regions outside the United States, where such harvest is prohibited under the . Large-scale commercial harvesting by Russian vessels in the Bering Sea and Sea of Okhotsk ended in 1994 following regulatory changes, though small-scale commercial takes from land-based and coastal operations persist at lower levels. In Japan, organized commercial hunts ceased decades ago, replaced by sporadic opportunistic hunting when ice conditions permit access. Historical data indicate that combined commercial and subsistence harvests across Russia and Alaska totaled fewer than 7,000 seals annually as of 1973, with Russia's contribution dominating prior to the 1990s decline. In the Sea of Okhotsk, commercial harvests of ice-associated seals, including spotted seals, remain regulated under quotas established in 1968, limiting vessel- and shore-based hunting to the May-June period; spotted seals typically comprise a minority fraction of the annual take, which has averaged under 10,000 total seals in recent decades. Subsistence harvests by Alaska Natives, while not commercial, supplement regional exploitation at levels of 5,000-6,000 seals per year, primarily for food and traditional uses. Bycatch in commercial fisheries poses a limited but persistent mortality source, with spotted seals entangled in gear such as salmon trap nets in Japan and trawls or gillnets in the North Pacific. In U.S. waters, estimated incidental mortality from commercial fisheries averaged 1.5 seals annually based on observer data through 2014, primarily in Bering Sea operations targeting pollock and other groundfish. Fishermen occasionally lethally deter seals raiding nets, exacerbating direct interactions beyond incidental capture. Overall, bycatch rates remain low relative to population size, but unquantified entanglements in international fisheries continue to contribute to cumulative mortality.

Threats and Conservation

Anthropogenic and Natural Threats

The primary anthropogenic threat to spotted seals is the reduction in sea ice due to climate change, which disrupts essential life history stages including whelping, nursing, molting, and resting, as these seals rely on stable pack ice in the Bering and Okhotsk Seas. This habitat loss is projected to intensify, with models indicating significant declines in suitable ice conditions by mid-century, particularly affecting the southern distinct population segment (DPS) in the Yellow and Bohai Seas, which was listed as threatened under the U.S. Endangered Species Act in 2010 due to vulnerability from accelerated ice melt. Additional pressures include ocean pollution, industrial noise from shipping and oil/gas exploration, and increased vessel traffic, which can disturb foraging and haul-out behaviors; in the Bohai-Yellow Sea region, anthropogenic activities exacerbate habitat fragmentation and elevate collision risks. Poaching for aquariums and direct human disturbance remain localized concerns, especially in Asian range areas. Natural threats to spotted seals encompass predation and disease. Predators such as killer whales (Orcinus orca), sharks, polar bears (Ursus maritimus), and walruses (Odobenus rosmarus) occasionally target pups and adults, with risks heightened when ice loss forces seals onto terrestrial sites lacking natural cover. Disease outbreaks, including brucellosis caused by Brucella spp., pose risks to reproductive success through placental infections and abortions, as documented in Alaskan populations where seroprevalence has been detected. While overall population trends remain stable in northern ranges, these natural factors can compound anthropogenic stressors during periods of environmental instability.

Conservation Measures and Research

The spotted seal (Phoca largha) is classified as Least Concern on the IUCN Red List, indicating that the species does not face a high risk of extinction in the wild due to its relatively large and widespread populations across the North Pacific. This assessment, last evaluated in 2016, accounts for an estimated global population exceeding 400,000 individuals, though data deficiencies persist for some regional subpopulations. In the United States, the Southern Distinct Population Segment (DPS)—encompassing seals in the southern Bering Sea and Sea of Okhotsk—was listed as threatened under the Endangered Species Act in December 2020, primarily due to projected habitat loss from declining sea ice associated with climate change. This listing triggers federal requirements for conservation actions, including minimization of incidental take during fisheries operations and development of recovery plans, though no critical habitat has been designated as the DPS occurs largely outside U.S. jurisdiction. Nationwide, spotted seals receive protection under the Marine Mammal Protection Act of 1972, which prohibits harassment, hunting, or capture except for limited subsistence harvest by Alaska Native communities. Internationally, measures vary: in China, the species is nationally listed as endangered with efforts focused on habitat protection in the Yellow Sea and Bohai Gulf, including artificial breeding programs and population monitoring to address local declines. In Russia, quotas regulate commercial harvests, though enforcement challenges persist in shared Bering Sea stocks. Research on spotted seals emphasizes population monitoring, use, and impacts, with NOAA Fisheries conducting periodic stock assessments through aerial surveys and photographic counts in the Bering and Chukchi Seas; for instance, the Bering Sea stock was estimated at around 141,000 individuals in 2012, with trends showing stability but vulnerability to ice loss. Recent advancements include haul-out behavior studies to refine abundance estimates, incorporating drone imagery and statistical modeling to correct for underwater individuals, as detailed in a 2024 NOAA project enhancing data for ice seals including spotted seals. The Alaska Department of Fish and Game collects biological samples from subsistence harvests to assess health metrics such as body condition, reproduction rates, and contaminant levels, providing indices of population status. Satellite telemetry has revealed movement patterns, with a 2023 study tracking individuals around Baengnyeongdo Island in South Korea to map preferences and foraging ranges. Genetic analyses indicate low differentiation across large distances (>1,000 km), supporting panmictic management in core areas but highlighting isolated southern groups. Modeling efforts project future distribution shifts under scenarios, estimating potential 30-50% reduction by 2050 in ice-dependent breeding grounds. Ongoing international collaborations, such as those under the North Pacific Marine Science Organization, integrate local indigenous knowledge with for comprehensive monitoring.

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