Threatened and Endangered Species - Recovery Plans
Date Published: December 2004
Number of Pages: 103
Author(s): Monique M. Lance, Scott A. Richardson and Harriet L. Allen
Sea otters existed along the Washington coast for thousands of years before they were extirpated by an intensive harvest for their valuable pelts that began in the mid-1700s. From about 1911 to 1969, sea otters were absent from the state. In 1969 and 1970, 59 sea otters were reintroduced to the Washington coast from Amchitka Island, Alaska. The sea otter was listed as a state endangered species in 1981, due to its small population size, restricted distribution, and vulnerability.
From 1989 to the most recent survey in 2004, the population has been growing at an average annual rate of 8.2%. From 2000 to 2004, annual survey counts have ranged from 504 to 743 sea otters. The current sea otter range in Washington extends from just south of Destruction Island on the outer coast to Pillar Point in the Strait of Juan de Fuca, with concentrations in the vicinities of Destruction Island, Perkins Reef, Cape Johnson, Sand Point, Cape Alava, and Duk Point. A few individual sea otters have been seen in Puget Sound and the San Juan Islands as well as along the Oregon coast.
The current distribution of sea otters in Washington includes only a portion of the pre-exploitation range, which extended south to the Columbia River with a major concentration off of Point Grenville and northward along the Olympia Peninsula and into the Strait of Juan de Fuca. At the present time, Washington sea otters occupy almost exclusively rocky habitat along the Olympic Peninsula coast and western Strait of Juan de Fuca. It is not possible to predict whether the population will continue to grow and spread and, if so, at what rate or in which direction. If they do expand their distribution, they could disperse into historically occupied sandy habitat to the south (e.g. Grays Harbor and Willapa Bay), spread eastward along the Strait of Juan de Fuca and into Puget Sound, or move north across the Strait of Juan de Fuca to Vancouver Island where more than 2,500 sea otters exist in British Columbia. Habitat-based carrying capacity estimates for the historic sea otter range in Washington vary from 1,372 to 2,734 otters, based on four measures of habitat availability.
Sea otters feed primarily on benthic invertebrates, consuming many pounds of prey each day to meet their high metabolic needs. In Washington, they consume shellfish species including sea urchins, clams, crabs and mussels. Studies in Washington and elsewhere have shown that sea otter predation on sea urchins may indirectly enhance the growth of kelp and kelp-associated communities. Shellfish are important to commercial, recreational, and tribal fisheries in Washington and predation by sea otters in a specific area can be significant and result in localized fisheries management issues.
Oil spills are the single greatest anthropogenic threat to sea otters. Washington’s sea otter population is particularly vulnerable to oil spills because it is concentrated along a relatively small geographic stretch of coastline where vessel traffic is steady. The relatively isolated nature of the current population also has implications for genetic diversity that intensify if a catastrophic event such as an oil spill were to occur. Recent studies indicate infectious diseases may be an important mortality factor in sea otters and warrant continued monitoring. Entanglement in fishing nets may cause significant losses in some parts of the sea otter range. In Washington, a small number of sea otters are taken in tribal gill net fisheries along the northern coast. These issues and others, combined with the species’ popular appeal, necessitate management and recovery efforts for sea otters in Washington, as they have for sea otter populations in Alaska, California, and British Columbia.
Goals of the Washington sea otter recovery program are to implement strategies that will ensure a selfsustaining sea otter population in Washington through the foreseeable future; and to manage the Washington sea otter stock in a manner consistent with the federal Marine Mammal Protection Act, other state and federal laws, court rulings and federal treaties with Native American tribes. The recovery plan outlines strategies which, when implemented, will enhance sea otter habitat and populations to the point where the long-term survival of the species in nature can be ensured and it can be downlisted from state Threatened status.
Recovery objectives are based on achieving population levels of 60-80 percent of the estimated carrying capacity (K) for Washington. Sea otters will be considered for downlisting from State Endangered to State Threatened status when: 1) the average population level over a 3-year period equals or exceeds 1,640 sea otters (60% of K) in Washington, and 2) Washington’s sea otter population is distributed such that a single catastrophic event, such as a major oil spill, would be unlikely to cause severe decline or extirpation of the population. Sea otters will be considered for downlisting from state Threatened status when the average population level over a 3-year period equals or exceeds 2,187 sea otters (80% of K), and management plans or agreements are in place by the state’s co-managers that provide for the continued viability of the sea otter population in Washington. Sea otter recovery strategies include conducting research and monitoring to determine abundance, distribution and health of the population, protection of sea otters and their habitat, prevention and preparation for oil spills, exchange of information, increased public education and outreach and development of cooperative, proactive management approaches among involved entities to reduce potential future sea otter-fishery conflicts.
Lance, M.M., S.A. Richardson and H.L. Allen. 2004. Washington state recovery plan for the sea otter. Washington Department of Fish and Wildlife, Olympia. 91 pp.
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