Spotted seal release - Photo: Dave Withrow
Spotted seal release - Photo: Dave Withrow
About the Species
The spotted seal gets its name from its coat pattern, which is usually a light-colored background with dark spots. Spotted seals are widely distributed on the continental shelf of the Beaufort, Chukchi, southeastern East Siberian, Bering, and Okhotsk Seas; south through the Sea of Japan; and into the northern Yellow Sea. From late fall through spring, spotted seal habitat use is primarily associated with seasonal sea ice. Most spotted seals spend the rest of the year making periodic foraging trips from haul-out sites onshore or on sea ice. Spotted seals are unusual among true seals in that they annually form "family" groups consisting of a female, a male, and a pup during breeding season.
Spotted seals rely on sea ice during reproduction and to some extent during molting. As such, they are sensitive to changes in the environment that affect the annual timing and extent of sea ice formation and breakup.
Spotted seals, like all marine mammals, are protected under the Marine Mammal Protection Act. There is one recognized stock of spotted seals in U.S. waters: the Alaska stock. One distinct population segment of spotted seals outside U.S. waters (the southern distinct population segment, DPS)—with breeding concentrations in the Yellow Sea and the Sea of Japan—is listed as threatened under the Endangered Species Act. Because of its listed status, this DPS is also designated as depleted under the MMPA.
Population Status
No accurate range-wide abundance estimates exist for spotted seals. Based on crude estimates available in historic literature, the worldwide population of spotted seals is estimated to be more than 500,000 individuals.
There is one recognized stock of spotted seals in U.S. waters: the Alaska stock. Abundance estimates for this stock are provided in the stock assessment report.
Historically, subsistence harvest of spotted seals has been moderately low and is not anticipated to increase significantly. While the United States does not allow the commercial harvest of marine mammals, such harvests are permitted in some other portions of the species’ range. Based on available data, these harvests are not thought to have been high enough historically to cause significant reductions in abundance and appear to be generally limited.
Protected Status
ESA Threatened - Foreign
MMPA Protected
MMPA Depleted
Appearance
Spotted seals have a round head, narrow snout, and small body, as well as narrow, short flippers. Adult spotted seals are silvery-gray to light gray with dark spots scattered densely on their body. Pups are born with a white coat that is usually shed at the time of weaning and replaced with a coat that is rather similar to adults. Spotted seals grow to average lengths of 5 feet, with weights ranging from 140 to 250 pounds. Males and females are generally similar in appearance. Spotted seals are closely related and often confused with harbor seals in areas where you can find both, such as in Bristol Bay, Alaska.
Behavior and Diet
Spotted seals prefer arctic or sub-arctic waters and are often found within the outer margins of shifting ice floes. They rarely inhabit areas of dense pack ice. During the breeding season, spotted seals primarily haul out on ice floes, whereas during the summer months they can be found in the open ocean or hauled out on shore.
Spotted seals consume a broad variety of mostly fishes and some crustaceans and cephalopods. While regional differences in the diet of spotted seals are noted among studies, some prey items are important across almost the entire range of the species. Pacific herring and crustaceans are major prey in all locations except the central Bering Sea, and walleye pollock is important in all regions except the Chukchi Sea. Overall, younger animals predominantly consume crustaceans, and older seals mainly eat fish. Spotted seals are not deep divers and feed almost exclusively over the continental shelf in waters less than 650 feet deep.
Where They Live
Spotted seals live in the waters of the North Pacific Ocean. They are widely distributed on the continental shelf of the Beaufort, Chukchi, southeastern East Siberian, Bering, and Okhotsk Seas; south through the Sea of Japan; and into the Yellow Sea.
In U.S. waters, spotted seals migrate south from the Chukchi Sea through the Bering Strait from October to November ahead of advancing sea ice. They spend the winter in the Bering Sea in the annual pack ice over the continental shelf. During spring, they migrate to coastal habitats after the sea ice retreats.
World map providing approximate representation of the Spotted seal's range
Lifespan & Reproduction
Nearly all spotted seals reach sexual maturity by the time they are 5 years of age. Spotted seal pups are born anytime from January through April, depending on their location. The pupping and nursing season occurs earliest (January through early March) in the Yellow Sea and latest (late March through May) in the Sea of Okhotsk and Bering Sea, with a peak of pup births in the Bering Sea in early to mid-April. Females mate shortly after their pups are weaned. Males are thought to be annually monogamous, and spotted seals form "family" groups consisting of a female, male, and a pup during breeding season. Gestation lasts for just over 10 months. Their maximum lifespan is 30 to 35 years.
Pups are born with a white natal coat (lanugo) which is shed around the time of weaning, and weigh 15 to 26 pounds at birth. They are nursed for 3 to 6 weeks, during which time they more than triple in weight. Pups born on the sea ice rarely enter the water until they are weaned and molted. During the first few weeks after weaning, pups remain at least partially dependent on ice while they become proficient at diving and foraging for themselves.
Threats
Climate Change
Spotted seals are primarily associated with sea ice during reproduction and molting. As such, spotted seals are sensitive to changes in the environment that affect the timing and extent of sea ice formation and breakup. In particular, loss of sea ice habitat poses a significant threat to the Southern distinct population segment (DPS) of spotted seals, which breeds in the Yellow Sea and Peter the Great Bay in the Sea of Japan.
Additional Factors of Potential Concern
The continuing decline in summer sea ice in recent years has renewed interest in using the Arctic Ocean as a potential waterway for coastal, regional, and trans-Arctic marine operations, which pose varying levels of threat to spotted seals depending on the type and intensity of the shipping activity and its degree of spatial and temporal overlap with the seals. Offshore oil and gas exploration and development could also impact spotted seals. The most significant risk posed by these activities is accidentally or illegally discharging oil or other toxic substances, which would have immediate and potentially long-term effects. Spotted seals could also be directly affected by noise and physical disturbance of habitat associated with such activities.
Scientific Classification
| Animalia |
Chordata |
Mammalia |
Carnivora |
Phocidae |
Phoca |
largha |
