Steller sea lions are large marine mammals inhabiting the North Pacific Ocean. As the largest eared seals, they are important to marine ecosystems. This article explores their habitats and range.
Global Geographic Distribution
Steller sea lions are found across the North Pacific Ocean, primarily inhabiting cool-temperate and subarctic coastal waters. Their extensive range stretches from northern Hokkaido, Japan, through the Kuril Islands, the Sea of Okhotsk, and across to the Aleutian Islands and Bering Sea. Their distribution continues along the southern coast of Alaska, through British Columbia, and southward to central California. While typically found in coastal waters over the continental shelf, they also forage in deeper pelagic areas, especially during the non-breeding season.
Essential Habitat Features
Within their range, Steller sea lions select specific terrestrial and aquatic habitats. They frequently use rocky islands, remote coastlines, and offshore islets as haul-out sites. These locations provide safe places for resting, molting, and protection from terrestrial predators.
Rookeries are traditional sites where sea lions gather between May and August to give birth, mate, and nurse their young. These terrestrial sites, including gravel or sandy beaches, ledges, and rocky reefs, are important for reproduction and early pup development. Proximity to rich feeding grounds, often in continental shelf waters, is also important for supporting these large predators.
Regional Differences and Subpopulations
The global Steller sea lion population is recognized as two distinct stocks based on genetic and demographic differences: the Eastern Stock and the Western Stock. They are separated by a dividing line at 144° West longitude, near Cape Suckling in Alaska.
The Eastern Stock ranges from California north to Southeast Alaska, including British Columbia, Washington, and Oregon. This stock has shown signs of recovery and was delisted from the U.S. Endangered Species Act as threatened in 2013, reflecting positive population growth. In contrast, the Western Stock occupies the Gulf of Alaska, the Aleutian Islands, the Bering Sea, and extends into Russian waters. This stock experienced significant declines and remains listed as endangered under the U.S. Endangered Species Act.
Conservation and Habitat Protection
Their habitats are directly linked to their conservation. Historically, populations declined, leading to their listing under the Endangered Species Act. Protecting their habitat involves addressing threats like human disturbance, which can cause abandonment of haul-out and rookery sites.
Other threats include competition with commercial fisheries for prey, entanglement in fishing gear, and the broader impacts of climate change on prey availability. Marine pollution also poses a risk. Protection efforts include designating critical habitat areas, often with buffer zones around major rookeries and haul-out sites to minimize disturbances.