Eumetopias jubatus ssp. monteriensis
|Scientific Name:||Eumetopias jubatus ssp. monteriensis|
|Species Authority:||(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 sub-species designation for the two stocks based on morphological and genetic studies. The Society for Marine Mammalogy subsequently recognized two subspecies of Eumetopias jubatus, E. j. jubatus (called the Western Steller Sea Lion) and E. j. monteriensis (called the Loughlin’s Steller Sea Lion; Committee on Taxonomy 2014). This assessment deals with Loughlin’s Steller Sea Lion.
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Gelatt, T. & Sweeney, K.|
|Facilitator/Compiler(s):||Lowry, L., Ahonen, H., Pollock, C.M., Chiozza, F. and Battistoni, A.|
Loughlin’s Steller Sea Lion has shown a steady increase in abundance with an annual growth rate of 2.85% over the past three generations. The population is projected to have reached an estimated 80,938 animals in 2015. There are no threats currently limiting this population, and continued growth is anticipated although a slowing in the trend during the last half of this period suggests that density dependent factors may be taking effect. The agency responsible for management of Steller Sea Lions in the USA conducted a species status review in 2013 and as a result Loughlin’s Steller Sea Lion was removed from the US List of Endangered and Threatened Species. Loughlin’s Steller Sea Lion does not meet any IUCN criteria for a threatened classification and is listed as Least Concern.
|Previously published Red List assessments:|
|Range Description:||Loughlin’s Steller Sea Lions (commonly described as the eastern distinct population segment of the Steller Sea Lion; NMFS 2008) normally occur from central California north along the west coast of North America to Cape Suckling, Alaska at 144° W latitude (NMFS 2013). The majority of the breeding population is in the northern portion of the range with approximately 43% of the population in Southeast Alaska and 41% in British Columbia. Oregon (11%) and California (5%) contain the remainder of the population. Their southernmost breeding location is at Año Nuevo Island in central California.|
Native:Canada (British Columbia); United States (Alaska, Aleutian Is., California, Oregon, Washington)
|FAO Marine Fishing Areas:|
Pacific – eastern central; Pacific – northeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Abundance of Loughlin’s Steller Sea Lion declined in the 1950s and 1960s due to government sanctioned culling in British Columbia and Alaska. In the early 1970s, laws were enacted to protect the species, and abundance has increased since then (Pitcher et al. 2007). The population was estimated to number between 58,334 and 72,223 in 2009 (NMFS 2013). It is projected to have reached an estimated 80,938 in 2015 based on count data collected up to 2010 (Canada), 2013 (west coast USA), and 2015 (Alaska) (NMFS, unpublished data) and projected using the agTrend model (Johnson and Fritz 2014). Over the past three generations (30 years), the annual growth rate has been 2.85% (95% CL 2.39% – 3.31%), and total abundance is estimated to have increased by 243%. At least three new rookeries became established in southeast Alaska during that time (Matthews et al. 2011), and a new rookery complex of at least two islands on the outer coast of Washington state has been established with at least 110 pups born in the summer of 2015 (NMFS unpublished data).|
A population viability analysis of Loughlin’s Steller Sea Lions was conducted as part of the 2008 Steller Sea Lion Recovery Plan (NMFS 2008). Based on an increasing trend and the elimination of the primary threat (USA and Canadian government-sanctioned culling) the probability of quasi-extinction of this subspecies was determined to be 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 reproductive rate of Loughlin’s Steller Sea Lion is unknown, but the pregnancy rate of mature female Western Steller Sea Lions was found to have declined during the 1970s and 1980s and was estimated to be 55% in the 1980s (Pitcher et al. 1998). 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). The generation time of approximately 10 years used in this assessment was derived from collections made in the Gulf of Alaska during the 1970s and 1980s of Western Steller Sea Lions (Calkins and Pitcher 1982) and a recent model (Van de Kerk et al. 2013).
Loughlin’s 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).
Survival rates of Sea Lions in Southeast Alaska were calculated based on animals marked as pups between 2001 and 2005 by the Alaska Department of Fish and Game (Hastings et al. 2011). This work indicated that first year pup survival averaged 0.60 for males and 0.64 for females. Survival to age 7 averaged 0.39 for females and 0.26 for males and differed according to the natal rookery. Pups born at the most recently established rookery in the northern portion of the range were 2.8 times more likely to survive to age 7 than those born in the southernmost Alaska rookery (Hastings et al. 2011).
Loughlin’s Steller Sea Lions are primarily found from the coast to the outer continental shelf and slope. They sometimes leave haulouts in very large groups; however, sightings at sea are most often of groups of 1-12 animals. Seasonal aggregations are known to occur in local areas of ephemeral prey abundance in Southeast Alaska (Womble et al. 2005, Sigler et al. 2009) and may exceed 4,500 animals in one particular location (Jemison et al. 2015). Loughlin’s Steller Sea Lions have been known to move westward into the range of the Western Steller Sea Lion, and Jemison et al. (2013) showed that westward movement was more common for males than females. Breeding bulls have been documented to travel >6,500 km round trip from southern Alaska to the Bering Sea and back within a single year (Jemison et al. 2013). 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 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 (Loughlin et al. 2003, Rehberg and Burns 2008) but can be to as much as 427 m (NMFS unpublished data). 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 yearlings routinely dive to depths of around 140 m for periods of two minutes. Juvenile Sea Lions satellite-tagged in Southeast Alaska and Washington State displayed deeper average dive depths, higher dive rates, and longer dive durations than juveniles in the western stock of Alaska (Loughlin et al. 2003, Pitcher et al. 2005). The diving of adult males has not been studied.
Loughlin’s Steller Sea Lions feed on many varieties of fish and invertebrates. Much of the information on diet comes from animals living in southeast Alaska, where they feed on Walleye Pollock, Pacific Cod, Flatfishes, Rockfishes, Herring, Salmon, Sand Lance, Skates, Squid, and Octopus (Trites et al. 2007). Adult females with young pups feed extensively at night, switching to foraging at any time after the breeding season. Sea Lions have been reported to kill and consume Harbor Seals in Glacier Bay National Park, Alaska.
The primary predators of 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 Steller Sea Lion 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 important to the subsistence cultures of people living near them for thousands of years. The average number of Loughlin’s Steller Sea Lions taken in Alaska was estimated at 12 per year for the period 2004-2008. More recent data are not available. A small number may also be taken by subsistence hunters in Canada (Allen and Angliss 2014).|
|Major Threat(s):||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 incidentally caught and 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 this population, and the increasing population trend and the decision of NMFS to remove this population from the ESA endangered list (NMFS 2013) confirms that conclusion.|
|Conservation Actions:||Loughlin’s Steller Sea Lions are protected in the USA and Canada. The entire species (E. jubatus) was listed as threatened under the ESA in 1990, and in 1997 the western population (corresponding to E. j. jubatus) 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 in 1993, including no entry zones near rookeries and management of fisheries activity in the vicinity of rookeries. 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 of the Western Steller Sea Lion, and to promote recovery of the species (NMFS 2008). The agency responsible for management of Steller Sea Lions in the United States, NMFS, conducted a species status review and found the eastern population increased >3% per year since the 1970s and therefore removed this subspecies from the ESA endangered and threatened species list (NMFS 2013). The western population in the USA is still listed as endangered under the ESA. Steller Sea Lions receive protection in Canada as a species of Special Concern under the Species at Risk Act of 2002.|
|Citation:||Gelatt, T. & Sweeney, K. 2016. Eumetopias jubatus ssp. monteriensis. The IUCN Red List of Threatened Species 2016: e.T17345844A66991740.Downloaded on 28 April 2017.|
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