top of page

Marine Science in the News: Sea otters in Elkhorn Slough

Sea otters are quite often the topic of conversation within the marine science and conservation communities. They are undoubtedly intelligent marine mammals recovering from a severely taxing life history, prompting many studies about their behavior and conservation. Studies over the last 20 years have focused on estuarine habitat use by sea otters, and one estuary in particular has been spotlighted: Elkhorn Slough.

Elkhorn Slough is a 7-mile-long estuary and tidal slough located about 22 miles south of Santa Cruz. It is one of the largest estuaries in California and the large tidal tract provides shelter and food for over 700 species, including the recovering sea otter. The threats faced by sea otters have been severe, almost wiping out the species entirely in the early 1900s. Despite a challenging life history, sea otters are recovering and their expansion into southern and northern habitats along the California coastline are an indication of successful ongoing conservation efforts.

Sea otter history

Historically, thousands of sea otters inhabited estuaries from the Aleutian Islands down along the California coastline but the fur-trapping industry nearly wiped out the sea otters. Prior to gaining protection from the International Fur Seal Treaty in 1911, sea otters were almost extinct with only 1,000 to 2,000 otters remaining. A group of only around 300 otters remained near Big Sur, California by the 1930s. These southern, or California sea otters (Enhydra lutris nereis) were protected and the population began a slow and steady recovery process. Despite gaining further protection through the Marine Mammal Protection Act in 1972 and the Endangered Species Act in 1973, sea otters are still listed as endangered.

Sea otters and Elkhorn Slough

Southern sea otters have lived in Elkhorn Slough full-time since 2000. The quiet slough waters provide a perfect refuge and sea otters have plenty to eat with the abundant crabs, clam, oyster, abalone and sea urchin populations. Check out the live Elkhorn Slough OtterCam here! Teams of researchers from federal, state and local institutions are studying habitat use by sea otters to evaluate ecosystem health and conservation efforts. Elkhorn Slough will likely play an important role in sea otter population monitoring, and teams of scientists will continue to research these animals to understand how to better protect them from further decline.

Other links:

To read more about current work and studies evaluating sea otter health and their habitat use, please visit “Elkhorn Slough Sea Otter Research” from the USGS Western Ecological Research Center.

Also visit “Elkhorn Slough Mammals: Sea Otter” at, the official website of the Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve, for further information.


bottom of page