Adult male Northern Fur Seals are much larger than females, attaining a length of 1.9m (6 ft) and weight of 200 kg (450 lbs) compared to 1.3 m (4 ft) and 35 kg (80 lbs) for females. Pups weigh 4.5-5.5 kg (10 – 12 lbs) at birth and are nursed for 4 months, during which time they increase 2 – 3 fold in weight. Females can live to about 25 years wheras males rarely live longer than 15 years. The pelage of both sexes is greyish brown and includes a dense layer of underfur.
The Northern Fur Seal has been hunted commercially for its fur since the late 1700's. Most seals were taken on rookeries, although many were also taken at sea during the late 1800's and early 1900's. Victoria was an important port for these pelagic sealing operations. For most of this century only young males, aged 3 – 5 years, have been harvested on the rookeries. Under the terms of the Interim Convention on Conservation of North Pacific Fur Seals, Canada received 15 per cent of the skins from harvests of the Pribilof Islands and Asian rookeries. However, the Convention expired in 1984 and only subsistence sealing is now permitted on the Pribilof Islands.
As part of Canadas obligation under the Interim Convention, the reproductive biology, diet and food requirements of this species were studied extensively at the Pacifc Biological Station during 1958-80. Northern Fur Seals feed mainly on small schooling fishes. In waters off B.C., 20% of the diet is salmon and 43% herring. The amount of food consumed varies with season, but adult females typical eat about 2.5 kg (5.5 lbs) of prey daily. However, the total amount of fish consumed off B.C. cannot be precisely determined because of the difficulty in estimating the numbers of seals wintering off our coast. Few fishers in B.C. consider Northern Fur Seals to be a serious problem.
Behaviour and Biology
Fur seals inhabiting the eastern North Pacific congregate on the Pribilof Islands in the Bering Sea during June to October to give birth and mate. When animals leave the rookeries in November they disperse widely throughout the eastern North Pacific, but tend to be most concentrated over the continental shelf. Most adult females and a few juveniles migrate to California and pass wouith through B.C. waters in early winter and north in late spring. Some individuals remain off the B.C. coast during winter and spring, but few come closer than 10 miles to shore. Most adult males remain in the Gulf of Alaska during the non-breeding season.
The Northern Fur Seal is found in off-shore waters throughout the North Pacific Ocean from the latitudes of southern California and southern Japan into the Bering and Okhotsk Seas. The eastern North Pacific stock numbers about 900,000 seals. This stock has declined in recent years, for reasons which are not clear. One likely cause is increased mortality of juveniles, many of which drown each year from entanglement in plastic debris, such as discarded nets and packing bands. Two other stocks, with a combined population size of about 400,000 seals, are found off the Asian coast.
Based on recent status report work (DFO 2007), “Northern Fur Seals inhabit the North Pacific and comprise a single population. During the pelagic migration, about 375,000 (30% of the population) winter along the west coast of North America (California to SE Alaska), with about one-third of those inhabiting Canadian waters during their peak abundance in May”. DFO (2007) also indicates that “the abundance of northern fur seals has declined from 1.7 million to 1.2 million over the last 30 years (3 generations). The decrease occurred at the largest breeding area on the Pribilof Islands; abundance at other breeding areas has not changed or has increased....The cause of the fur seal decline on the Pribilof Islands is unknown, but does not appear to be due to direct human-induced mortality".
This species is considered Threatened in Canada by COSEWIC (COSEWIC 2006), a recommendation "made on the basis of a 54% decline in pup production during 1974-2004 at the Pribilof Islands". "The population that breeds on the Pribilof Islands in the Bering Sea feeds in, and migrates through, British Columbia waters" (COSEWIC 2006).
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2021-05-12 5:44:07 PM]
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