Threatened and Endangered Species - Status Reports
Date Published: February 2018
Number of Pages: 29
Author(s): Chris L. Sato
Sea otters originally ranged along the Pacific coast from northern Hokkaido, Japan, through eastern Russia to the Aleutian and Pribilof Islands, and along the coast of mainland Alaska south to British Columbia, Washington and California. Sea otters in Washington historically ranged from the Columbia River to near Port Angeles. The species was exploited during the heyday of the fur trade beginning in 1792, and was extirpated in the state by 1910. The sea otter has been classified as a state endangered species in Washington since 1981.
Sea otters were reintroduced to Washington in 1969 and 1970, when 59 animals were translocated to sites at Point Grenville and La Push from Amchitka Island, Alaska. The current Washington population is descended from between 10 to 43 individuals that survived these introductions. The population numbered 208 animals when combined aerial and ground surveys were first conducted in 1989, and has steadily grown since then. The sea otter population’s current range in Washington encompasses the outer coast from Point Grenville in the south to Pillar Point on the Strait of Juan de Fuca. Distribution patterns have changed as the population has grown.
Washington’s sea otter population is restricted to a roughly 130-kilometer stretch of outer coast along the Olympic Peninsula. The population has shown strong growth, averaging 9.5 percent per year since 1989 and has increased to a 3-year running average of 1,753 individuals from 2015 through 2017. This exceeds the downlisting objective in the 2004 Recovery Plan of 1,640 sea otters over a 3-year period.
Range expansion is another objective of the 2004 Recovery Plan. Suitable habitat for expansion is available along the Strait of Juan de Fuca and north to Vancouver Island. There is also potential for range expansion south into unoccupied habitat such as Grays Harbor and Willapa Bay, although anthropogenic habitat alteration in those areas may curtail movement. Currently there is no consensus on why sea otters are not clearly expanding into available habitat.
Despite a steady increase in numbers and density, the Washington sea otter population is at risk of losing significant numbers should a catastrophic event such as a large oil spill occur off Washington’s coast. Sea otters also remain at risk from disease, toxins, and effects of climate change. Studies have found that genetic exchange between the British Columbia and Washington sea otter populations is occurring, but to an unknown degree. Interbreeding between the Washington and British Columbia populations may lessen the impact of a catastrophic event by contributing to repopulation and through an increase in overall genetic fitness of the remaining Washington population.
Given the steady and substantial increase in numbers and evidence of genetic exchange with the British Columbia sea otter population, the sea otter is no longer “seriously threatened with extinction throughout all or a significant portion of its range within the state,” which is the definition of an endangered species. It is recommended that the sea otter be reclassified to state threatened in Washington.
Sato, C. L. 2018. Periodic Status Review for the Sea Otter in Washington. Washington Department of Fish and Wildlife, Olympia, Washington. 23+iii pp.
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