Eumetopias jubatus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	MAMMALIA	CARNIVORA	OTARIIDAE

Scientific Name:

Eumetopias jubatus

Species Authority

(Schreber, 1776)

Common Name/s:

English

–

Steller Sea Lion, Northern Sea Lion, Northern Sealion, Steller's Sea Lion, Steller's Sealion

Assessment Information [top]

Red List Category & Criteria:

Endangered A2a ver 3.1

Year Assessed:

2008

Assessor/s

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

Evaluator/s:

Kovacs, K. & Lowry, L. (Pinniped Red List Authority)

Justification:
The eastern and western stocks of Steller Sea Lions are showing opposite trends, with slight increases in the east and renewed declines in the west. The causes of the severe decline of the western stock of Steller Sea Lions during the 1970s and 1980s remain unknown, although some causes have been eliminated as likely threats to recovery. The global population of Steller Sea Lions qualifies for Endangered (EN) status because of the overall global decline of 54% in the last three generations. It is particularly concerning that the cause of the declines has not yet been identified.

IUCN Evaluation of the Steller Sea Lions, Eumetopias jubatus
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.

Generation time in Steller Sea Lions is approximately 10 years. Steller Sea Lions have experienced a dramatic decline over the last three generations (30 years) but the causes are not clearly reversible, nor understood (global decline is, however, not > 50%). The decline has slowed and even stopped in some areas but still persists in others such as the western Aleutians.

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.

Steller Sea Lions experienced a dramatic overall decline between about 1970 and 2000 (three generations). The population has been split into two stocks with the eastern stock showing a 3% increase while the western stock declined at a rate as high as 15% annually in the 1980s and overall declined about 70% between the late 1970s and 1990. The overall reduction in abundance of the species between the mid 1970s and 2007 is estimated to be 54%. The reasons for the precipitous declines of the past two decades and the continued, slowed decline is unknown and may not be reversible. The Steller sea lion therefore meets the criterion for Endangered.

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.

The overall population of Steller Sea Lions has increased slightly since 2000 due to a continued 3% per year increase in the eastern stock and a slowing of the decline in the western stock. However, if the trend analysis includes data from prior to 2000 the predicted future trend would be negative.

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.

Steller sea lions have experienced a population reduction and this reduction could continue into the future for unknown causes

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 Steller Sea Lions is >20,000 km²

B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²

The AOO of Steller Sea Lions 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

Both segments of the Steller Sea Lion population exceed 10,000 mature individuals.

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

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 < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5

Both segments of the Steller Sea Lion population exceed 1,000 mature individuals.

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 have been many population viability analyses conducted on Steller Sea Lions. Results have been consistent and indicate that if only the western segment of the population is considered it has a high probability of declining to a low level. Even the most conservative analyses found that the probability of quasi-extinction of the western segment within 100 years was approximately 10%. However, since the eastern segment is showing an increase, it is likely that for the entire population of Steller Sea Lions, the probability of extinction is < 10% in 100 years and thus it does not qualify for listing under this criterion.

Listing recommendation — The eastern and western stocks of Steller Sea Lions are showing opposite trends, with slight increases in the east and renewed declines in the west. The causes of the severe decline of the western stock of Steller Sea Lions during the 1970s and 1980s remain unknown, although some causes have been eliminated as likely threats to recovery. The global population of Steller Sea Lions qualifies for Endangered (EN) status because of the general, overall level of decline from 1957-2007 of 54% (criterion A2a), and the continued decline, for unknown reasons in the western stock.

History:

1996	–	Endangered (Baillie and Groombridge 1996)
1994	–	Vulnerable (Groombridge 1994)

Geographic Range [top]

Range Description:	Steller Sea Lions are found from central California (formerly southern California), north along the west coast of North America to the Aleutian Islands, and west along the Aleutian chain to the Kamchatka Peninsula, and from there south along the Kuril Islands to northern Japan, the Sea of Japan, and possibly to both Koreas. Steller Sea Lions also occur in the Sea of Okhotsk, west of Kamchatka and the Kuril Islands. From the Aleutians they range north across the Bering Sea to the Bering Strait. Vagrants have been recorded in China, and at Herschel Island in the Beaufort Sea (Rice 1998).
Countries:	Native: Canada; Japan; Russian Federation; United States Vagrant: China; Korea, Democratic People's Republic of; Korea, Republic of
FAO Marine Fishing Areas:	Native: Pacific – eastern central; Pacific – northwest; Pacific – northeast
Range Map:	(click map to view full version)

Population [top]

Population:	The worldwide population of Steller Sea Lions declined by 64% during the period from 1960 to 1989, and is currently estimated to be between approximately 105,800-117,800 animals. The decline has been most dramatic in the large populations from the Gulf of Alaska (-54%), west throughout the Aleutian Island chain (-81%), to the moderately-sized Russian population (-74%). The most recent estimates, derived from the last complete surveys of pups (2005) and non pups (2004) in western Alaska (Fritz et al. 2005), Russia (Burkanov and Loughlin 2005), and the population known as the “Eastern Stock” which includes all Steller Sea Lions east of 144° (Pitcher et al. 2007) suggest an overall decline from the mid 1970s in excess of 50%. Several population viability analyses conducted on Steller Sea Lions (e.g. York et al. 1996, Gerber and Van Blaricom 2001, Winship and Trites 2006, NMFS Steller Sea Lion Final Draft Recovery Plan 2008). Results have been consistent and indicate that the western segment of the population has a high probability of declining to a low level. Even the most conservative of the analyses found that the probability of quasi-extinction of the western segment within 100 years was approximately 10%.
Population Trend:	Decreasing

Population:

The worldwide population of Steller Sea Lions declined by 64% during the period from 1960 to 1989, and is currently estimated to be between approximately 105,800-117,800 animals. The decline has been most dramatic in the large populations from the Gulf of Alaska (-54%), west throughout the Aleutian Island chain (-81%), to the moderately-sized Russian population (-74%). The most recent estimates, derived from the last complete surveys of pups (2005) and non pups (2004) in western Alaska (Fritz et al. 2005), Russia (Burkanov and Loughlin 2005), and the population known as the “Eastern Stock” which includes all Steller Sea Lions east of 144° (Pitcher et al. 2007) suggest an overall decline from the mid 1970s in excess of 50%.

Several population viability analyses conducted on Steller Sea Lions (e.g. York et al. 1996, Gerber and Van Blaricom 2001, Winship and Trites 2006, NMFS Steller Sea Lion Final Draft Recovery Plan 2008). Results have been consistent and indicate that the western segment of the population has a high probability of declining to a low level. Even the most conservative of the analyses found that the probability of quasi-extinction of the western segment within 100 years was approximately 10%.

Population Trend:

Decreasing

Habitat and Ecology [top]

Habitat and Ecology:	Steller Sea Lions are the largest otariids and the fourth largest pinniped. Both sexes are robust and powerfully built at all ages. They are sexually dimorphic, with adult males weighing three times as much, and growing 20-25% longer than adult females. Pups are born with a thick blackish-brown lanugo that is moulted by about 6 months of age. The maximum length of adult males is about 3.3 m and average weight is 1000 kg. The maximum length for adult females is about 2.5 m and average weight is 273 kg. Pups are born at an average of about 1 m and 18-22 kg. The age of maturity is 3-6 years for females, and 3-7 years for males (Calkins and Pitcher 1982). Males are not able to defend territories before they are 9 years old (L. Lowry pers. comm.). The annual pregnancy rate of mature females declined during the 1970’s and 1980’s and was estimated to be 55% in the 1980’s based on collections at sea (Pitcher et al. 1998). Recent age-structured modelling based on population counts from the central Gulf of Alaska indicates that the birth rate in 2004 was 36% lower than in the 1970’s (Holmes et al. 2007). Gestation lasts one year, including a delay of implantation of about 3 months. Females may live up to 30 years old and males to about 20 years (Reijnders et al 1993). Steller Sea Lions are highly polygynous and breed in the late spring and summer. Adult males arrive before females and those that are nine years or older establish themselves on territories, which they aggressively and vociferously defend. Steller sea lions have deep voices and produce powerful low-frequency rolling roars and can be heard for long distances over the noise of wind and waves. Pups are born from May through July, and females stay continuously ashore with their newborns for the first week to ten days after giving birth. Following this period of attendance, females make foraging excursions, primarily at night for periods of 18-25 hours, followed by time ashore to nurse their pup. Females come into estrous and mate about two weeks after giving birth. Weaning can occur before the next breeding season, but it is not unusual to see females nursing yearlings or older juveniles. Throughout their range, Steller Sea Lions are primarily found from the coast to the outer continental shelf and slope. However, they frequent and cross deep oceanic waters in some parts of their range. Steller Sea Lions occasionally leave haulouts in very large groups; however, sightings at sea are most often of groups of 1-12 animals. They aggregate in areas of prey abundance, including near fishing vessels, where they will feed on netted fish and by-catch. Steller sea lions are known to haulout on sea ice. They are not considered migratory; juveniles and subadults make the longest distance trips. Adults usually forage and live near their natal colonies and return to these sites to breed. The area used by adult females for foraging in winter increases dramatically over the area used in the summer and females tend to dive deeper in winter than summer. Diving is generally to depths of 200 m or less and dive duration is usually two minutes or less, with both parameters varying by season and age of the animal Diving ability of pups and juveniles increases with age, and they routinely dive to depths of around 140 m for periods of two minutes as yearlings. The diving of adult males has not been studied. Steller Sea Lions feed on many varieties of fish and invertebrates. Much of the information on diet comes from animals living in Alaska, where Steller Sea Lions feed on walleye pollock, Pacific Cod, Atka Mackerel, herring, sand lance, several varieties of flatfish, salmon and rockfish, and invertebrates such as squid, octopus, bivalves and gastropods (Sinclair and Zeppelin 2002, Trites et al. 2007). Adult females with young pups feed extensively at night, switching to foraging at any time after the breeding season. Steller sea lions are known to kill and consume young and small northern fur seals at the Pribilof Islands, and also have been reported to kill and consume Harbour and Ringed seals, and possibly Sea Otters. The primary predators of Steller Sea Lions are Killer Whales. Sleeper Sharks in Alaska have been found with Steller Sea Lion remains in their stomachs, but it is unknown whether the prey was scavenged and in any case they are not believed to be primary predators. Great White Sharks presumably take Steller pups within the areas where their range overlaps.
Systems:	Terrestrial; Marine

Habitat and Ecology:

Steller Sea Lions are the largest otariids and the fourth largest pinniped. Both sexes are robust and powerfully built at all ages. They are sexually dimorphic, with adult males weighing three times as much, and growing 20-25% longer than adult females. Pups are born with a thick blackish-brown lanugo that is moulted by about 6 months of age. The maximum length of adult males is about 3.3 m and average weight is 1000 kg. The maximum length for adult females is about 2.5 m and average weight is 273 kg. Pups are born at an average of about 1 m and 18-22 kg.

The age of maturity is 3-6 years for females, and 3-7 years for males (Calkins and Pitcher 1982). Males are not able to defend territories before they are 9 years old (L. Lowry pers. comm.). The annual pregnancy rate of mature females declined during the 1970’s and 1980’s and was estimated to be 55% in the 1980’s based on collections at sea (Pitcher et al. 1998). Recent age-structured modelling based on population counts from the central Gulf of Alaska indicates that the birth rate in 2004 was 36% lower than in the 1970’s (Holmes et al. 2007). Gestation lasts one year, including a delay of implantation of about 3 months. Females may live up to 30 years old and males to about 20 years (Reijnders et al 1993).

Steller Sea Lions are highly polygynous and breed in the late spring and summer. Adult males arrive before females and those that are nine years or older establish themselves on territories, which they aggressively and vociferously defend. Steller sea lions have deep voices and produce powerful low-frequency rolling roars and can be heard for long distances over the noise of wind and waves.

Pups are born from May through July, and females stay continuously ashore with their newborns for the first week to ten days after giving birth. Following this period of attendance, females make foraging excursions, primarily at night for periods of 18-25 hours, followed by time ashore to nurse their pup. Females come into estrous and mate about two weeks after giving birth. Weaning can occur before the next breeding season, but it is not unusual to see females nursing yearlings or older juveniles.

Throughout their range, Steller Sea Lions are primarily found from the coast to the outer continental shelf and slope. However, they frequent and cross deep oceanic waters in some parts of their range. Steller Sea Lions occasionally leave haulouts in very large groups; however, sightings at sea are most often of groups of 1-12 animals. They aggregate in areas of prey abundance, including near fishing vessels, where they will feed on netted fish and by-catch. Steller sea lions are known to haulout on sea ice.

They are not considered migratory; juveniles and subadults make the longest distance trips. Adults usually forage and live near their natal colonies and return to these sites to breed. The area used by adult females for foraging in winter increases dramatically over the area used in the summer and females tend to dive deeper in winter than summer. Diving is generally to depths of 200 m or less and dive duration is usually two minutes or less, with both parameters varying by season and age of the animal Diving ability of pups and juveniles increases with age, and they routinely dive to depths of around 140 m for periods of two minutes as yearlings. The diving of adult males has not been studied.

Steller Sea Lions feed on many varieties of fish and invertebrates. Much of the information on diet comes from animals living in Alaska, where Steller Sea Lions feed on walleye pollock, Pacific Cod, Atka Mackerel, herring, sand lance, several varieties of flatfish, salmon and rockfish, and invertebrates such as squid, octopus, bivalves and gastropods (Sinclair and Zeppelin 2002, Trites et al. 2007). Adult females with young pups feed extensively at night, switching to foraging at any time after the breeding season. Steller sea lions are known to kill and consume young and small northern fur seals at the Pribilof Islands, and also have been reported to kill and consume Harbour and Ringed seals, and possibly Sea Otters.

The primary predators of Steller Sea Lions are Killer Whales. Sleeper Sharks in Alaska have been found with Steller Sea Lion remains in their stomachs, but it is unknown whether the prey was scavenged and in any case they are not believed to be primary predators. Great White Sharks presumably take Steller pups within the areas where their range overlaps.

Systems:

Terrestrial; Marine

Threats [top]

Major Threat(s):	Steller Sea Lions have been important to the subsistence cultures of people living near them for long periods. Native Alaskans currently take about 300 a year for food and other products. The reasons for the large declines in the population, which were especially acute in some portions of the range during the period 1960 to 1989 are unclear, but are the subject of intensive ongoing investigations. Factors hypothesized include: the direct and indirect effects of large-scale commercial fisheries on key Steller sea lion prey species, long-term ecosystem shifts, and changes in behaviour by a primary predator, the killer whale. Steller Sea Lions are killed in nets in fisheries off Alaska. An unknown number may be shot during commercial fishing operations. Tissue contaminant levels are generally low in most parts of their range. Deliberate killing by fishermen, disease, incidental take by fisheries, and reduced food supply have been suggested as factors which may have contributed to the current decline (Lowry et al. 1989, Reijnders et al. 1993, Loughlin and York 2000). The Steller Sea Lion Recovery Team identified and ranked threats to recovery of the western stock and used a weight of evidence approach to assess the relative impact. The team recognized three threats as “potentially high”: environmental variability, competition with commercial fisheries and killer whale predation. Similarly, Atkinson et al. (2008) recently reviewed the suspected anthropogenic sources of mortality for the same stock of Steller Sea Lions and concluded that competition with fisheries and the potential impacts of contaminants could not be excluded as continuing threats to recovery.

Major Threat(s):

Steller Sea Lions have been important to the subsistence cultures of people living near them for long periods. Native Alaskans currently take about 300 a year for food and other products. The reasons for the large declines in the population, which were especially acute in some portions of the range during the period 1960 to 1989 are unclear, but are the subject of intensive ongoing investigations. Factors hypothesized include: the direct and indirect effects of large-scale commercial fisheries on key Steller sea lion prey species, long-term ecosystem shifts, and changes in behaviour by a primary predator, the killer whale.

Steller Sea Lions are killed in nets in fisheries off Alaska. An unknown number may be shot during commercial fishing operations. Tissue contaminant levels are generally low in most parts of their range. Deliberate killing by fishermen, disease, incidental take by fisheries, and reduced food supply have been suggested as factors which may have contributed to the current decline (Lowry et al. 1989, Reijnders et al. 1993, Loughlin and York 2000). The Steller Sea Lion Recovery Team identified and ranked threats to recovery of the western stock and used a weight of evidence approach to assess the relative impact. The team recognized three threats as “potentially high”: environmental variability, competition with commercial fisheries and killer whale predation. Similarly, Atkinson et al. (2008) recently reviewed the suspected anthropogenic sources of mortality for the same stock of Steller Sea Lions and concluded that competition with fisheries and the potential impacts of contaminants could not be excluded as continuing threats to recovery.

Conservation Actions [top]

Conservation Actions:	The Steller Sea Lion is protected in the United States and Canada, and the Commonwealth of Independent States (Russia) is proposing to add it to their “red” species list. In the United States the Steller Sea Lion is listed as Depleted under the U.S. Marine Mammal Protection Act. The species was listed as Threatened in 1990 with the Western Population moved to Endangered in 1997 under the U.S. Endangered Species Act. A draft recovery plan for Steller Sea Lions was prepared in 1992, and a new assessment team was initiated in 2001. A draft and publication are planned for spring 2008. Critical habitat was designated in 1993, including no entry zones near rookeries and management of fisheries activity in the vicinity of rookeries. A groundfish management that strategically disperses fisheries over areas and time was put in force in 2003. Extensive funding has been applied to Steller Sea Lion research to develop information on ecology, behaviour, genetics, population dynamics, and movements to assist in the development of management activities, to attempt to understand the reasons for the decline and to promote recovery of the species.

Conservation Actions:

The Steller Sea Lion is protected in the United States and Canada, and the Commonwealth of Independent States (Russia) is proposing to add it to their “red” species list. In the United States the Steller Sea Lion is listed as Depleted under the U.S. Marine Mammal Protection Act. The species was listed as Threatened in 1990 with the Western Population moved to Endangered in 1997 under the U.S. Endangered Species Act. A draft recovery plan for Steller Sea Lions was prepared in 1992, and a new assessment team was initiated in 2001. A draft and publication are planned for spring 2008. Critical habitat was designated in 1993, including no entry zones near rookeries and management of fisheries activity in the vicinity of rookeries. A groundfish management that strategically disperses fisheries over areas and time was put in force in 2003. Extensive funding has been applied to Steller Sea Lion research to develop information on ecology, behaviour, genetics, population dynamics, and movements to assist in the development of management activities, to attempt to understand the reasons for the decline and to promote recovery of the species.

Citation:	Gelatt, T. & Lowry, L. 2008. Eumetopias jubatus. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 23 November 2008.
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