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Northern Fur Seal (Callorhinus ursinus)

Status | Taxonomy | Species Description | Habitat | Distribution |
Population Trends | Threats | Conservation Efforts | Regulatory Overview |
Key Documents | More Info
 


Northern fur seal
Northern Fur Seal
(Callorhinus ursinus)
Photo: NMFS National Marine Mammal Laboratory


Northern fur seal range map
Northern Fur Seal Range Map
(click for larger view PDF)

 

 

 
  what marine mammals eat- video screenshot
Video: What do Northern fur seals eat? And, how do we find out what they eat?
Credit: Alaska Fisheries Science Center, NOAA Ocean Media Center


Status
MMPA Depleted - Pribilof Island/ Eastern Pacific stock
(All other stocks are still protected under the MMPA, but not considered depleted.)

Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Otariidae
Genus: Callorhinus
Species: ursinus

Species Description
Weight: up to 130-600 pounds (60-270 kg), with males being much heavier than females
Length: up to 5-7 feet (1.5-2 m), with males being larger than females
Appearance:  stocky body, small head, and a very short snout htat is brown, gray, or black in color
Lifespan: 10-27 years, with females living longer than males
Diet: fish and squid
Behavior: Males establish territories early in the breeding season (in May)

Northern fur seals are members of the "eared seal" family (Otariidae). They have a stocky body, small head, and a very short snout. Their flippers are the longest in the Orariidae family--their hind flippers can measure up to one-fourth of their total body length.

Adult males are much heavier and longer, with much larger necks, shoulders, and chests, than females. Males can grow to 7 feet (2 m) and weigh up to 600 pounds (270 kg) while females can grow to 5 feet (1.5 m) and weigh up to 130 lb (60 kg). Northern fur seals have very dense coats that end at the wrist line of their flippers. Pups are uniformly black until they molt when they are around 3 months old. Adult males are dark brown to black, and adult females are dark gray or brown on their backs and light gray, silver, or cream on their throat, chest, and stomach.

The lifespan of fur seals is approximately 10 years for males and 27 years for females.

Males establish territories early in the breeding season in May. Females arrive around mid-June to early July and give birth to one pup. The peak of pupping is usually in early July. During the breeding season, females alternate between feeding at sea, where they forage for fish and squid, and nursing on shore. While females are foraging, pups play and sleep in groups with other pups (often called "puppy pods"). Adult males present on breeding beaches do not forage while maintaining territories. Upon returning, mothers identify their pups from vocalizations and, when closer, scent. Pups are weaned at 4-5 months (late October-early November). When the breeding season ends, animals travel south and remain "pelagic" for the winter migration period (from October-November to May-June). Females travel farthest south, and pups scatter in all directions on their first migration, but eventually make their way south.

Habitat
Northern fur seals primarily use two types of habitat:

  • open ocean for foraging
  • rocky beaches for reproduction

Adult fur seals spend more than 300 days per year (about 80% of their time) foraging at sea. In the open ocean, concentrations of fur seals may occur around major oceanographic features such as seamounts, canyons, valleys, and along the continental shelf break because of the availability of prey in those places. The North Pacific Transition Zone is an important productive region. Breeding seals tend to haul-out on rocky beaches, but colonies can use broad sandy beaches as well.

  Northern fur seal range map
Northern Fur Seal Range Map
(click for larger view PDF)


Distribution
Northern fur seals breed at six locations in the North Pacific and Bering Sea. Three of these locations--Pribilof Islands, Bogoslof Island and San Miguel Island--are in the United States. The other three--Commander Islands, Kuril Island, and Robben Islands--are in Russia.

The Pribilof Islands support the largest breeding rookery of northern fur seas (about half of the world's fur seal population).

In the winter, the southern boundary of the northern fur seal range extends across the Pacific Ocean, between southern California and the Okhotsk Sea and Honshu Island, Japan. In the spring, most fur seals migrate north to breeding colonies in the Bering Sea. Male northern fur seals leave the breeding colony in September, and spend most of their time in the Bering Sea and North Pacific Ocean along the Aleutian Islands. Females return to sea by late October, and generally travel to either the central North Pacific or south along the California coast to feed. Some fur seals may spend all year around San Miguel Island.

northern fur seal breeding colonies
Northern Fur Seal Breeding Colonies and Extent of their Winter Range
(map from Conservation Plan [pdf])

Population Trends
The Pribilof Island population was designated as "depleted" under the Marine Mammal Protection Act (MMPA) in 1988 because it had declined by more than 50% since the 1950s. Recent trends show that northern fur seal populations on the Pribilof Islands have continued to decline.

The Eastern Pacific stock is currently estimated at about 600,000 animals from a historical high of 2.1 million in the late 1940s to early 1950s. On the Pribilof Islands of St. Paul and St. George, the estimated pup production has declined 5.2% per year since 1998. Conversely, fur seal abundance on Bogoslof Island increased through the 1990s (58% per year from 1988 to 1997) and continues to increase. NMFS currently allows a subsistence harvest by Alaskan natives based on need. This is not thought to be a cause of continued population decline. The number of fur seals taken for subsistence purposes ranges from about 1,800 seals on St. Paul Island and about 400 on St. George Island.

The first fur seals to populate San Miguel Island likely migrated from the Pribilof Islands. The population grew steadily in the 1950s and early 1960s (46%), but experienced declines from major El Niño events. The population began to recover in 1999, and recent estimates of San Miguel Island are over 9,000. A small population has developed on South Farallon Island (off the California coast), presumably immigrants from San Miguel Island.

The Commander Islands, Kuril Islands, and Robben Islands in Asia experienced a severe decline of northern fur seals in the early 1900s from commercial sealing. The number of seals declined on all three islands between the late 1960s and the late 1980s. The Robben Island population now appears to be recovering.

Threats
Historical declines were caused by

  • commercial harvest
    • After unregulated "pelagic" harvests were stopped in 1911, the fur seal population recovered, and by the 1950s was thought to be at pre-harvest levels. The most recent decline began soon after an experimental female harvest was implemented in 1956 to increase the productivity of the herd. Although the consequences of this program were recognized within a few years and the female harvest ended in 1968, the northern fur seal population on the Pribilof Islands continued to decline.
    • Regulated commercial harvests ended on St. George Island in 1976 and on St. Paul Island in 1984.

Today, northern fur seals face a variety of threats including:

  • predation
  • changes in the availability of prey
  • bycatch in fishing gear
  • habitat change
  • entanglement in marine debris
  • disturbance from vessels and humans
  • climate change
  • environmental pollutants

The factors affecting northern fur seal survival are poorly understood, particularly while the animals range outside the Bering Sea. Studies of Steller sea lions, which have experienced similar population declines, suggest that factors limiting recovery include changes in quantity and quality of prey and possible increased predation by killer whales.

Reduced survival rates of northern fur seal adult females and juveniles may also limit recovery.

Conservation Efforts
International agreements to conserve declining fur seals were made with Great Britain (for Canada), Japan, Russia, and the United States in 1911 and again in 1957. In 1984, the U.S. ended commercial harvest of northern fur seals within U.S. waters.

Under the MMPA, extensive monitoring and research has focused on the Pribilof Island and San Miguel Island populations. NMFS' conservation plan [pdf] is focused on identifying and lessening impacts from human related threats such as marine debris and incidental take in commercial fishing gear.

Co-management agreements of northern fur seals with the tribal governments of St. Paul and St. George (Pribilof Islands), especially regarding subsistence harvest, are another aspect of NMFS' conservation plan. Through this arrangement, the U.S. and tribal governments are implementing programs that promote full utilization of edible and inedible parts of northern fur seals, promote community outreach and education efforts, monitor shorelines and rookeries through the Island Sentinel Program, and monitor and remove marine debris. The tribal governments of St. Paul and St. George also maintain and repair research infrastructure on fur seal rookeries.

Regulatory Overview
Northern fur seals were afforded protection in U.S. waters under The Fur Seal Treaty of 1911 [pdf].

The Pribilof Island/ Eastern Pacific population of the northern fur seal was designated as "depleted" under the Marine Mammal Protection Act in 1986.

NMFS issued a Conservation Plan for the Eastern Pacific Stock of Northern Fur Seals in 2007.

Key Documents
(All documents are in PDF format.)

Title Federal Register Date

Annual harvest estimates for 2014-2016 subsistence taking on Pribilof Islands, AK

  • Proposed Harvest Estimates
79 FR 45728


79 FR 27550
08/06/2014


05/14/2014
Notice of a Petition to Revise Regulations on Subsistence "Taking" of Northern Fur Seals
75 FR 21243 04/23/2010
Conservation Plan for Eastern Pacific Stock 72 FR 73766 12/28/2007
71 FR 32306 06/05/2006
Conservation Plan for the Eastern Pacific Stock of Northern Fur Seals   1997
MMPA Depleted Designation 53 FR 17888 05/18/1988
Stock Assessment Reports n/a various

More Information

Updated: October 8, 2014

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