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Sea Otter Population History in Washington State

Steve Jefferies, WDFW, 2015 WA sea otter surveys

Sea otters have inhabited the northern coasts of the Pacific Ocean since the Pleistocene, about 1 to 3 million years ago. By 1740, when the Bering expedition explored the coasts of the Aleutian and Commander Islands, there were between 100,000 and 300,000 sea otters on the Pacific coast.

Photo: 2015 WA Sea otter surveys, Steve Jefferies/WDFW

  • Sea otter fur is extraordinarily dense, providing excellent insulation in cold ocean waters. Their fur has up to 1 million hairs per square inch, more than any other mammal. It is considered some of the finest fur in the world. Native Americans on the Pacific coast hunted sea otters throughout their range, but the abundant populations encountered by early Russian hunters indicate that otters were not widely overhunted before contact with Europeans. Between 1740 and 1900, Russian and American fur traders harvested the sea otter almost to extinction in order to profit from their fur.

    By 1900, commercial harvest had essentially ceased for the simple reason that it was difficult to locate a sea otter; they had been reduced to 13 tiny remnant populations totaling no more than a few hundred each. In 1911, the International Fur Seal Treaty halted commercial hunting of sea otters.

    Once commercial harvest ceased, sea otter populations rebounded and re-colonized much of their former range between Prince William Sound, Alaska west to the Kuril Islands. However, by the 1950s they became extinct along the Pacific coast from Prince William Sound south to Baja California, with the exception of one remnant population in California.

    During the 1960s and 1970s, the Alaska Department of Fish and Game reintroduced sea otters into former habitat in Alaska, Canada, Washington, and Oregon in collaboration with other State and Provincial wildlife management agencies. In 1987, otters were reintroduced to San Nicholas Island in southern California. Due to these efforts, sea otter populations in southeast Alaska, British Columbia, and Washington are currently stable or increasing, but have not yet rebounded to pre-commercial harvest levels.

    The sea otter population in Washington was listed as “endangered” under Washington State’s Endangered Species Act in 1981, due to its small population size, restricted distribution, and vulnerability. Currently, the Washington sea otter population size is distributed primarily between Pillar Point in the Strait of Juan de Fuca to just south of Destruction Island on the outer coast. A few individual sea otters are occasionally seen in Puget Sound and the San Juan Islands, as well as along the Oregon coast. As of 2010, the Washington sea otter population totals just over 1,000 otters.

    Oil spills are the single greatest threat to sea otters throughout their range. The most striking example was the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, which spilled 11 tons of crude oil and killed approximately 3,905 sea otters (range 1,904-11,257). Washington’s sea otter population is particularly vunerable to oil spills because it is concentrated along a relatively small geographic stretch of coastline where vessel traffic is steady.

    In December 2004, Washington Department of Fish and Wildlife released their Sea Otter Recovery Plan. The goals of their recovery program are to implement strategies that will ensure a self-sustaining sea otter population in Washington through the foreseeable future and to manage the Washington sea otter stock in a manner consistent with the Marine Mammal Protection Act, other federal and state laws, court rulings, and federal treaties with Native American tribes.


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