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The annual rangewide southern sea otter census has been temporarily modified to adapt to limitations that prevented surveys from airplanes in 2021 to 2023 for a subset of the California sea otter range. Shore-based surveys were completed, and the hope is to return to full census surveys in 2024. 

WERC Sea otter at Elkhorn Slough National Estuarine Research Reserve
A sea otter at Elkhorn Slough National Estuarine Research Reserve near Moss Landing, Calif.

The annual southern sea otter surveys are conducted cooperatively by scientists of the U.S. Geological Survey, California Department of Fish and Wildlife, Monterey Bay Aquarium, U.S. Fish and Wildlife Service, and U.S. Navy and with the help of experienced volunteers. The survey extends across the southern sea otter range, about 375 miles of California coast, from Half Moon Bay south to Santa Barbara, and includes a spring survey at San Nicolas Island. The information gathered is used by federal and state wildlife agencies in making sea otter-related management decisions. 

The sea otter census has two parts: surveys conducted by shore-based observers along shore-accessible areas, and surveys conducted from a small airplane. The airplane survey was not completed in 2011 and from 2020 through 2023 due to a combination of weather conditions, COVID-related health precautions, and limitations in plane availability. On the other hand, the shore-based survey has been completed every year since 1982, with only the exception of 2020 when the census was cancelled. Sea otter survey counts are used to indicate the population trend of California sea otters. However, no single year's survey result is indicative of a population change, and inconsistencies in survey coverage among years can lead to biases in trend estimates. The USGS is developing a modified analysis based on three-year averages of southern sea otter counts from the 2021 through 2023 census years adapted to only the shore-surveyed areas which comprise a subset of the California sea otter range. Results will be released in late 2023 or early 2024. 

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