|Scientific Name:||Eumetopias jubatus|
|Species Authority:||(Schreber, 1776)|
|Infra-specific Taxa Assessed:|
Phoca jubata Schreber, 1776
|Taxonomic Notes:||In previous IUCN evaluations, Steller Sea Lions have been treated as a single species. The species was listed as two separate stocks (officially called “distinct population segments”) under the US Endangered Species Act (ESA) in 1997 based on the phylogeographic method (Loughlin 1997). Although the strongest evidence for stock separation at the time was the distribution of mtDNA haplotypes across the range, a divergence in population trend was also apparent. Phillips et al. (2009) published a manuscript that argued for subspecies designation for the two stocks based on morphological and genetic studies. The Society for Marine Mammalogy Committee on Taxonomy subsequently recognized two subspecies of Eumetopias jubatus; E. j. jubatus commonly known as the Western Steller Sea Lion, and E. j. monteriensis, commonly known as Loughlin’s Steller Sea Lion (Committee on Taxonomy 2014). The Pinniped Specialists Group has assessed the two subspecies independently. This assessment combines the assessments for the subspecies and reports the status of the entire species.|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor(s):||Gelatt, T. & Sweeney, K.|
|Contributor(s):||Fritz, L. & Burkanov, V.|
|Facilitator/Compiler(s):||Lowry, L., Ahonen, H., Pollock, C.M., Chiozza, F. and Battistoni, A.|
The Steller Sea Lion includes two recognized subspecies, the Western Steller Sea Lion and the Loughlin’s Steller Sea Lion. Western Steller Sea Lions experienced a dramatic and unexplained population decline of about 70% between the late 1970s and 1990. The population reached its low point in approximately 2000, and through 2015 has shown an overall annual increase of 1.8% per year in the USA. However, in the western Aleutian Islands Sea Lion numbers have continued to decline. Overall, the western subspecies had experienced a population reduction of approximately 50% during the last three generations and continues to meet IUCN criteria for Endangered. The Loughlin’s Steller Sea Lion population has increased steadily since 1979, and is projected to be 243% larger in 2015 than in 1985. That subspecies does not meet any of the criteria for IUCN threatened categories.
When the two subspecies are considered together, the large increase displayed by Loughlin’s Steller Sea Lion is enough to compensate for much of the decline elsewhere, such that the overall abundance of the species has declined by approximately 13% over the last three generations. This does not meet any of the criteria for IUCN threatened categories. However, because of the slower recovery of Western Steller Sea Lions and a continuing decline in a portion of their range, it is recommended that as a species, Steller Sea Lions should continue to be listed as Near Threatened as they almost qualify for a threatened listing under criterion A2a.
|Previously published Red List assessments:|
|Range Description:||Steller Sea Lions normally occur from central California north along the west coast of North America, westward through the Gulf of Alaska and the Aleutian Islands to the Kamchatka Peninsula, and from there south along the Kuril Islands to northern Japan and the Sea of Japan (Loughlin 2009). They also occur in the Sea of Okhotsk and the Bering Sea north to Bering Strait. Vagrants have been recorded in China, and at Herschel Island in the Canadian Beaufort Sea (Rice 1998). The western subspecies primarily occupies the area west of 144° W longitude. The eastern subspecies occurs from east of 144° W longitude south along the North American coast to central California.|
Native:Canada (British Columbia); Japan; Russian Federation (Kamchatka, Kuril Is.); United States (Alaska, Aleutian Is., California, Oregon, Washington)
Vagrant:China; Korea, Democratic People's Republic of; Korea, Republic of
|FAO Marine Fishing Areas:|
Pacific – northwest; Pacific – eastern central; Pacific – northeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The US National Marine Fisheries Service (NMFS) uses a Bayesian approach (agTrend; Johnson and Fritz 2014) to model all Steller Sea Lion survey data in the US range and to estimate the population trends presented here. Counts in the Alaska portion of the range are made from aircraft using standardized photographic methods. Counts in the Russian portion of the range are collected from shore or from small boats only.|
Counts of Western Steller Sea Lions declined by approximately 69% between 1977 and 2007 (NMFS 2008). Using historical counts (NMFS 2008 and unpublished data; Burkanov and Loughlin 2005, Burkanov unpublished data) and the most recent data from counts made in 2015 (NMFS unpublished data, Burkanov et al. in press, Burkanov, unpublished data) the decline for 1985-2015 (three generations) is estimated to be approximately 62% in the USA and 50% for the entire population, including Russia. However, despite continued declines in the western Aleutian Islands, overall abundance has increased in both the USA (1.8% per year) and in Russia since the early 1990s (86% total increase between early 1990s to 2013/2015). Total abundance of the Western population is estimated to be approximately 79,929 in 2015 with 55,791 in the USA and 24,138 in Russia. The Loughlin’s Steller Sea Lion population has increased at an average rate of more than 3% per year since 1979. Total abundance of this subspecies in 2015 is estimated from regional data up to 2010, 2013, and 2015 is approximately 80,938 (NMFS unpublished data). When the two subspecies are combined, the global abundance of Steller Sea Lions is estimated to be approximately 160,867 in 2015, which is a reduction of 13% since 1985.
Population viability analyses have been conducted for the Western and Loughlin’s Steller Sea Lion subspecies but not for the species as a whole. However, given that abundance of both subspecies is currently increasing the probability of extinction is certainly less than 10% in 100 years.
|Current Population Trend:||Increasing|
|Habitat and Ecology:||Steller Sea Lions are the largest otariids and the fourth largest pinniped. Both sexes are robust and powerfully built. They are sexually dimorphic, with adult males weighing three times as much as, and growing 20–25% longer than, adult females. Pups are born with a thick blackish-brown lanugo that is molted by about six months of age. The maximum length of adult males is about 3.3 m and average weight is 1,000 kg. The maximum length for adult females is about 2.5 m and average weight is 273 kg. Pups are born at an average size of about 1 m and 18–22 kg (Loughlin 2009).|
The age of sexual 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 nine years old. The annual pregnancy rate of mature females in the western population declined during the 1970s and 1980s and was estimated to be 55% in the 1980s based on collections at sea (Pitcher et al. 1998). 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 1970s (Holmes et al. 2007). Gestation lasts one year, including a delay of implantation of about three months. Females may live to be up to 30 years old and males to about 20 years (Loughlin 2009). Here we use a generation time of 10 years based on life tables derived from collections made in the 1970s and 1980s (Calkins and Pitcher 1982), and other analyses (York 1994, Holmes and York 2003, Van de Kerk et al. 2013).
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 defend. Pups are born from May through July, and females stay continuously ashore with their newborns for the first 7–10 days after giving birth. Following this period of attendance, females make foraging excursions for periods of 18–25 hours, followed by time ashore to nurse their pup. Females come into oestrus 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 (Loughlin 2009). Recent work on vital rates indicates that age specific survival may differ across the range and second year survival is likely dependent on the age at weaning (Hastings et al. 2011, Fritz et al. 2014, Altukhov et al. 2015, Maniscalco et al. 2015).
Steller Sea Lions are primarily found from the coast, where they haul out on rocky shores, to the outer continental shelf and slope where they feed. However, they frequent and cross deep oceanic waters in some parts of their range. They sometimes leave haulouts in very large groups but 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 discarded bycatch. Steller Sea Lions sometimes haul out on sea ice where it is available. They may move long distances but are not considered migratory; juveniles and subadults make the longest trips. Adults usually forage and live near their natal colonies and return to those sites to breed. The area used by adult females for foraging in winter is much greater than the area used in the summer, and females tend to dive deeper in winter than summer. Overall, adults usually forage and use haul-out sites near their natal rookeries, where they typically return to breed. Adult females satellite-tagged in the US portion of the western stock made long pelagic foraging trips during winter, whereas their foraging range was more restricted during summer (Merrick and Loughlin 1997, Fadely and Lander 2012, Fadely et al. 2013). Adult females are capable of diving to depths of at least 427 m but average approximately 45 m; dives are deeper during winter than summer (NMFS, unpublished data). Dive duration is usually two minutes or less, but can exceed 13 minutes (Rehberg and Burns 2008). Dives of juveniles are generally shallow and short. Diving ability of pups increases with age (Loughlin et al. 2003, Fadely et al. 2005, Lander et al. 2010), with dives ranging on average from 5-35 m and up to 2 min (Loughlin et al. 2003, NMFS, unpublished data). Juvenile Sea Lions satellite-tagged in Southeast Alaska and Washington State made deeper average dives, and had higher dive rates and longer dive durations than juveniles in western Alaska (Loughlin et al. 2003, Pitcher et al. 2005). The diving of adult males has not been studied.
Steller Sea Lions feed on many types of fishes and invertebrates. Much of the information on diet comes from Alaska, where they feed on Walleye Pollock, Pacific Cod, Atka Mackerel, Herring, Sand Lance, several species of Flatfish, Salmon, and Rockfish, and invertebrates such as Squid and Octopus (Sinclair and Zeppelin 2002). Food habits analysis using samples collected between 1990 and 2009 indicate that Western Steller Sea Lions in the U.S. consumed similar prey by region throughout the time period, but the distribution range of prey use increased over time (Sinclair et al. 2013). Adult females with young pups feed primarily at night, switching to foraging at any time of day after the breeding season. Steller Sea Lions are known to kill and consume young northern Fur Seals at the Pribilof Islands, as well as Harbor and Ringed Seals.
The primary predators of Steller Sea Lions are Killer Whales (Loughlin 2009). Sleeper Sharks have been suggested as a potential predator of juvenile Western Steller Sea Lions in the Gulf of Alaska (Horning and Mellish 2014), although previous work in the same area found that none of the 198 Sharks examined near rookeries during summer contained Steller Sea Lion remains (Sigler et al. 2006).
|Continuing decline in area, extent and/or quality of habitat:||No|
|Generation Length (years):||10|
|Movement patterns:||Not a Migrant|
|Congregatory:||Congregatory (and dispersive)|
|Use and Trade:||Steller Sea Lions have been harvested for commercial purposes in both the USA (Alaska) and the Soviet Union/Russia, but commercial harvesting ceased decades ago. They have been used as a subsistence resource by indigenous people for thousands of years. The US Marine Mammal Protection Act allows Alaska Natives to take Steller Sea Lions for subsistence and creation of Native handicrafts, and currently they are primarily taken in communities in the northern Gulf of Alaska and Aleutian Islands (Haynes and Mishler 1991). The most recent (2007-2011) estimates of the overall average Alaska Native harvest were 199/year for the Western Steller Sea Lion and 11.3/year for the Loughlin’s Steller Sea Lion (Allen and Angliss 2014).|
The greatest threat to Loughlin’s Steller Sea Lions has been intentional culling in Southeast Alaska and Canada in the 1950s and 1960s. Those practices were discontinued in the early 1970s and the population has been increasing ever since. Some are killed in net fisheries off the west coast of North America. An unknown number may be shot during commercial fishing operations although it is generally believed that this source of mortality has been reduced greatly since the establishment of federal laws prohibiting killing of Sea Lions in Canada and the USA (NMFS 2013). The 2008 Steller Sea Lion Recovery Plan found that there were no apparent threats limiting the recovery of the Loughlin’s Steller Sea Lion population (NMFS 2008), and the increasing population trend confirms that conclusion.
Western Steller Sea Lions are listed as vulnerable in the Threatened Wildlife of Japan Red Data Book. Hattori and Yamamura (2014) reported that over 200 Steller Sea Lions were culled annually between 1960-1993 to reduce predation on commercial fish stocks. Recent work indicates that the annual culling was then reduced to a limit of 116/year until 2010 at which time a new 5 year quota of 1,030 culled Sea Lions was imposed. This resulted in an increased annual average take (Matsuda et al. 2015). In 2015 approximately 400 Steller Sea Lions were reported to be culled in Japan (Yamamura et al. 2015). In Russia, the major Steller Sea Lion rookeries were given protection under the Northern Fur Seal and Sea Otter Conservation Act in the late 1950s. They were listed as endangered (category 2) in the Russian Red Data Book in 1994 and harvest was prohibited. These measures had a positive effect in the western portion of the range as the population increased around Sakhalin Island, the Kuril Islands, and in the northern Sea of Okhotsk. However, abundance along the eastern coast of Kamchatka and in the Commander Islands has not recovered for unknown reasons (V. Burkanov pers. comm.).
In the USA the Steller Sea Lion is listed as depleted under the US Marine Mammal Protection Act. The species was listed as threatened under the ESA in 1990, and in 1997 the western population was uplisted to endangered. A recovery plan for Steller Sea Lions was approved in 1992, and a revised recovery plan was published in 2008. Critical habitat was designated under the ESA in 1993. No-entry zones were established around rookeries at the time of listing, and fisheries, particularly those operating in critical habitat, have been managed to reduce the likelihood of competitive interactions. Substantial funding has been made available for Steller Sea Lion research to develop information on ecology, behavior, genetics, population dynamics, and movements. Results have been used to assist in the development of management activities, to attempt to understand the reasons for the decline, and to promote recovery of the species (NMFS 2008). The fact that the overall growth rate of the western population is now positive suggests that at least some of these conservation efforts have had a beneficial effect. A species status review conducted in 2013 found that the Loughlin’s Steller Sea Lion population increased more than 3% per year since the 1970s and therefore it was removed from the ESA threatened species list (NMFS 2013). The western population in the USA is still listed as endangered under the ESA.
|Citation:||Gelatt, T. & Sweeney, K. 2016. Eumetopias jubatus. The IUCN Red List of Threatened Species 2016: e.T8239A45225749.Downloaded on 25 July 2017.|
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