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USGS Western Ecological Research Center

Sea Otter Research at WERC

Sea Otters
Sea otters (Enhydra lutris) are keystone predators in the nearshore environment of the eastern Pacific Ocean, in a food web composed of sea otter, sea urchin, and kelp forest. Without sea otters, the kelp forest can be overgrazed by sea urchins, which in turn can affect other species that depend on this ecosystem.

The geographical range once extended across the North Pacific Ocean from the central Pacific coast of Baja California, Mexico, to northern Japan. Prior to the Pacific maritime fur trade, which began with the discovery of Alaska and the Aleutian Islands by the Bering Expedition in the mid-1700s, sea otters probably occurred at high densities more or less continuously throughout this region. However, the species was systematically hunted to the brink of extinction by the end of the 19th century. Sea otters were afforded protection from further take in 1911. About a dozen remnant colonies survived at the time of protection, and with protection these colonies began to recover.

Populations in California and Alaska (Aleutian Archipelago) have declined in recent years. The California population was listed as "threatened" in 1977 under the U.S. Endangered Species Act. Research on sea otters is mandated by the Endangered Species Act and the Marine Mammal Protection Act.

WERC maintains expertise on sea otters in California, Washington, and Alaska, and works with state, federal, and local partners throughout the species' range. The Center is the repository for data on both the threatened California sea otter population and the state-listed Washington sea otter population. The Center's sea otter research program is based at the Santa Cruz Field Station. Current research focuses on population biology and behavior of California and Washington sea otters, including monitoring their status and trends and studying deaths caused by entanglement in fishing equipment, and predation of sea otters in marine ecosystems; contaminants in coastal ecosystems of the Aleutian archipelago; marine reserve design for the Bering Sea ecosystem; and interactions between sea otters and nearshore communities.

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Last update: 01 May 2003