|Scientific Name:||Callorhinus ursinus|
|Species Authority:||(Linnaeus, 1758)|
|Red List Category & Criteria:||Vulnerable A2b ver 3.1|
|Assessor(s):||Gelatt, T. & Lowry, L. (IUCN SSC Pinniped Specialist Group)|
|Reviewer(s):||Kovacs, K. & Lowry, L. (Pinniped Red List Authority)|
The Eastern stock of Northern Fur Seals is predominantly in the Pribilof Islands. This stock has experienced a significant, steep decline in recent years and has failed to recover despite the cessation of commercial harvesting. Although the global population is still over a million animals, the current downward trend in abundance remains a mystery. The most troubling aspect of the situation is that the Pribilof population’s pup production currently matches that during a time of very strong growth in the early 1900s (1918) yet the numbers continue to drop. Because this portion of the population represents approximately one half of the world-wide population, it seems that the species should be considered in the threatened category of Vulnerable under IUCN Red List Criterion A2 (due to the fact that the causes of the reduction do not appear to have ceased, are not understood, and may not be reversible based on the unknown cause). Thus, the Northern Fur Seal should remain classified as Vulnerable.
IUCN Evaluation of the Northern Fur Seal, Callorhinus ursinus
Prepared by the Pinniped Specialist Group
A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
Male Northern Fur Seals begin competing for a territory at approximately 7-9 years of age and females begin breeding after the age of four. Generation time is unknown but since females can breed successfully into their early twenties, it is likely in excess of 12-15 years. Northern Fur Seals have shown a significant decline in recent years but the reasons for the reductions are not fully understood, have not ceased despite a ban in commercial hunting and therefore are not clearly reversible.
A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
Although other areas within the range of the species have shown slight increases and the proportion of the population on the Pribilofs has decreased, St. Paul Island remains the largest Northern Fur Seal rookery in the world with over 122,000 pups born in 2004. Accordingly, some rookeries are decreasing in size. The Eastern Pacific stock of Northern Fur Seals (Pribilof Islands and Bogoslof Island) experienced a decline of >50% between the early 1950’s and 2005. However, this decline was at least in part due to a steady harvest of fur seals that ended on St. Paul Island in 1984. However, despite the cessation of the commercial harvest, the population in the Pribilofs has continued to decline and pup production on the largest rookery at St. Paul Island declined by over 22% between 2000 and 2004 and experienced an average annual rate of decline of 6% (SE = 0.7%) between 1998-2004. Although the overall world population has not declined as dramatically as that of the Pribilofs, because the Pribilofs represent almost half of the species population, the species should still be considered to be Vulnerable.
A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1.
A population reduction of northern fur seals is suspected in the future based on current trends at the largest rookeries. The likely amount of population reduction has not been projected, but if the current trend continues on the Pribilof Islands for the next 30 years, the population will move from being Vulnerable to being Endangered.
A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²
The EOO of Northern Fur Seals is > 20,000 km².
B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²
The AOO of Northern Fur Seals is > 2,000 km².
AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.
C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000
The current global abundance of Northern Fur Seals (all age classes) is approximately one million.
AND either C1 or C2:
C1. An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
(a ii) % individuals in one subpopulation: CR = 90–100%; EN = 95–100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.
D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; V number of mature individuals < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5
The current abundance of Northern Fur Seals is approximately one million. AOO is > 20 km² and the number of locations is > 5.
E. Quantitative analysis
Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years
There has been no quantitative analysis of the probability of extinction for Northern Fur Seals.
Listing recommendation— The Eastern stock of Northern Fur Seals is predominantly located in the Pribilof Island; this stock has experienced a significant, steep decline since the 1950’s that stabilized and then began dropping again recently. The reasons for the current downward trend remain a mystery. The most troubling aspect of this decline is that the Pribilof population currently has a pup production level similar to that in 1918, a time of strong growth, yet the numbers continue to drop. Because the Pribilof population represents approximately one half of the world-wide population the species should be considered in the threatened category of Vulnerable, based on A2b due to the fact that the causes of the reduction do not appear to have ceased, are not understood, and may not be reversible.
|Previously published Red List assessments:||
|Range Description:||Northern Fur Seals are a widely-distributed pelagic species in the waters of the North Pacific Ocean and the adjacent Bering Sea, Sea of Okhotsk and Sea of Japan. They range from Northern Baja California, Mexico north and offshore across the North Pacific to Northern Honshu, Japan. The southern limit of their distribution at sea is approximately 35° N. Vagrants reach the Yellow Sea in the west and eastern Beaufort Sea in the Arctic. The vast majority of the population breeds on the Pribilof Islands, with substantial numbers on the Commander Islands as well. Still other sites are used, including San Miguel Island in California, Bogoslof Island in the Bering Sea, and Robben Island off Sakhalin Island in Russia. Many animals, especially juveniles, migrate from the Bering Sea south to southern California or the waters off Japan, to spend the winter feeding.|
Native:Canada; Japan; Korea, Democratic People's Republic of; Korea, Republic of; Mexico; Russian Federation; United States
Vagrant:China; Taiwan, Province of China
|FAO Marine Fishing Areas:||
Pacific – eastern central; Pacific – northeast; Pacific – northwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The current global population was estimated to be approximately 1.1 million in 2004-2005. Abundance is declining. The overall decline is not proportional with the regions where the greatest decreases are occurring - in the Pribilof Islands – in fact, the small populations in the Kuril Islands and on Bogoslof Island in the Aleutians have increased. Approximate individual site population sizes are estimated as follows: Pribilof Islands: 688,028: Commander Islands: 225,000-230,000; Robben Island: 88,000; Kuril Islands: 45,000-50,000; San Miguel Island: 7,784 (Reijnders et al 1993). The Pribilof Islands population declined at 6.2% annually on St. Paul Island and 4.5% annually on St. George Island between 1998 – 2004 (Towell et al. 2006). Pup production on St. Paul again dropped, by 10.5% between 2004 and 2006. Once containing approximately 75% of the world population of northern fur seals, the Pribilofs currently have approximately 50%. Estimated pup production on St. Paul Island in 2004 was at a level equal to that observed in 1918, which was a time when the population was growing at a rate of 8% annually following cessation of the pelagic harvests (Towell et al. 2006), so the current declines are quite perplexing.|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Northern Fur Seals exhibit extreme sexual dimorphism, with males being 30-40% longer and more than 4.5 times heavier than adult females. Males can be as large as 2.1 m and 270 kg. Females can be up to 1.5 m and 50 kg or more. Newborns weigh 5.4-6 kg, and are 60-65 cm long. Pups are blackish at birth, with variable oval areas of buff on the sides, in the axillary area and on the chin and sides of the muzzle. After 3-4 months, pups moult to the colour of adult females and subadults. Northern Fur Seals become sexually mature at 3-5 years old, at which time females usually produce one pup a year for most of the rest of their lives. Gestation lasts 51 weeks, which includes a delay of implantation of 3.5 to 4 months. Longevity of this species is 25 years (Reijnders et al 1993). Males do not become physically mature, and large enough to compete for a territory that will be used by females, until they are 8-9 years old. The generation time for females is approximately 12-15 years depending on the determination methods used.
Breeding on the Pribilof Islands occurs from mid-June through August, with a peak in early July (the median date in southern California is approximately 2 weeks earlier than at the Pribilofs). This is a highly polygynous species. Males arrive at the rookeries up to one month before females and vocalize, display and fight to establish and maintain territories.
Northern Fur Seals usually give birth a day after arrival at the rookery. Mean time from birth to oestrous is 5.3 days, followed by a departure for a mean of 8.3 days for the first feeding trip. Females breeding at the Pribilof Islands are located relatively far from the foraging areas, which are concentrated at the edge of the continental shelf and hence females in this population consistently make longer foraging trips than most other female otariids, with a mean trip length of 6.9 days. Once foraging begins the mean depth of dives is 68 m and average duration is 2.2 minutes with maximum depth recorded of 207 m and maximum duration of 7.6 minutes. Pups are visited 8-12 times over the lactation period and attended for a mean of 2.1 days during each visit, before being abruptly weaned at 4 months old.
Northern Fur Seals are one of the most pelagic pinnipeds. They spend most of the year at sea, rarely (if ever) returning to land between one breeding season and the next. Thus, males spend an average of only 45 days ashore a year and females only 35 days a year. Once weaned, juveniles go to sea and do not haul-out until they return, usually to the island of their birth, 2-3 years later. At sea, Northern Fur Seals are most likely to be encountered alone or in pairs, with groups of 3 or more being uncommon. They forage relatively far from shore, over the edge of the continental shelf and slope. Diving is concentrated around dawn and dusk. Northern fur seals spend quite a bit of time rafting at the surface, either asleep or grooming. They employ a wide variety of resting postures, including raising one or more flippers into the air, and draping one of their fore flippers over both of the rear flippers to form a posture known as the "jug handle" position.
Many animals, especially juveniles, migrate from the Bering Sea south to California or the waters off Japan, to spend the winter feeding.
The diet varies by location and season and includes many varieties of epipelagic and vertically-migrating mesopelagic schooling and non-schooling fish and squid. Prey species of importance in the waters off California and Washington include anchovy, hake, saury, several species of squid and rockfish, and salmon. In Alaskan waters, Walleye Pollock, Capelin, Sand Lance, Herring, Atka Mackerel, and several species of squid are important prey.
Predators include Killer Whales, sharks, and Steller Sea Lions.
Northern Fur Seals have one of the longest and most complex histories of commercial harvesting, which began when the main breeding colonies were discovered in the late 18th century; exploitation continued through until 1984. Numerous international treaties and agreements were put in force over time in efforts to manage this species. There were many periods of decline and recovery over this long period. It is estimated that the population numbered up to 2.5 million animals in the 1950s. They may have been considerably more numerous than this level back when there were many more active rookeries, before the onset of exploitation by Europeans and Americans.
Northern Fur Seals compete for Walleye Pollock with one of the largest commercial fisheries world. Measurable annual mortality, especially for juveniles and subadults, is caused by entanglements in derelict and discarded fishing gear, marine debris and direct interactions with commercial fisheries. This mortality was highest during the period of active high seas drift net fishing in the North Pacific in the 1980s. But, entanglement in debris is an ongoing problem. Long-term ecosystem regime change in the North Pacific and possible changes in the foraging patterns of a key predator (the Killer Whale), may be working synergistically with the fisheries related issues to cause the current population decline.
Like all fur seals, Northern Fur Seals are vulnerable to oil spills because of their dependence on their thick pelage for thermoregulation. The small colonies at San Miguel Island in the California Channel Islands and on the Farallon Island may be at greatest risk due to proximity to major harbours, shipping lanes and offshore oil extraction facilities.
The effect of global climate change on this species is uncertain. However, any further negative disruption of the ecosystem of the northern fur seal should be considered a threat.
Small numbers of Northern Fur Seals are taken annually by Alaska Natives in a subsistence harvest on the Pribilof Islands. For the period 1999-2003, the average annual harvest was 869 animals; all animals taken were juvenile and sub-adult males. Subsistence harvest has declined in recent years to the level of 478 taken in 2007 on both Pribilof Islands (Lestenkoff and Zavadil 2007, Malavansky 2007).
|Conservation Actions:||Following the termination of the Interim Convention on the Conservation of the North Pacific Fur Seal in 1984, the Northern Fur Seal is now managed on land independently by the Commonwealth of Independent States and the United States. The eastern north Pacific stock of the Northern Fur Seal was listed as depleted under the U.S. Marine Mammal Protection Act in 1988, and a final conservation plan was completed in December 2007.|
|Citation:||Gelatt, T. & Lowry, L. (IUCN SSC Pinniped Specialist Group). 2008. Callorhinus ursinus. The IUCN Red List of Threatened Species 2008: e.T3590A9963699. http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T3590A9963699.en . Downloaded on 04 October 2015.|
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