Red List Category

Red List Criteria

Version

2008

Gelatt, T. & Lowry, L. (IUCN SSC Pinniped Specialist Group)

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
The EOO of Northern Fur Seals is > 20,000 km².

B2. Area of occupancy (AOO): CR
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 (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
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 or
(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 AND/OR restricted area of occupancy typically: AOO
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.