MWVCRC - Sea Otter Surveys

person looking into a telescope
A CDFW scientist using a telescope to search for sea otters.

Since 1982, a standardized method has been deployed to survey the sea otter population in California. The spring surveys have traditionally been used to assess population status because they are both consistently higher than fall surveys and show less variability. The fall survey data supplement the spring data to provide the necessary information to assess female reproductive rates and changes in reproductive success through time. The survey methodology consists of two-person teams using binoculars and spotting scopes that survey nearshore waters along accessible stretches of coastline. A fixed-wing aircraft (Partenavia PN68 Observer) with two observers, a data recorder and pilot conduct aerial surveys of the remaining areas. The aerial method is used to survey sections of the sea otter range that are not amenable to shore-based counts either because of accessibility, topography, or distance of animals from shore. These sea otter surveys are conducted cooperatively by scientists of the U.S. Geological Survey, California Department of Fish and Wildlife, U.S. Fish and Wildlife Service, Monterey Bay Aquarium and with the help of experienced volunteers. The information gathered is used by federal and state wildlife agencies to monitor trends in population dynamics and in making decisions about the management of this threatened species.

For the latest survey results, see the USGS sea otter survey page.


Laird Henkel
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