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California Sea Otter Surveys |
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A standardized method to survey sea otters was developed by WERC scientists and put into
use in 1982 in California. Survey procedures involve counting animals twice annually, in
early autumn and late spring. Two-person teams use binoculars and spotting scopes to count
individuals from accessible stretches of coastline and from fixed-wing aircraft in the
remaining areas. The counts made from shore are plotted on maps and then entered into a
spatial database. The aerial counts are entered directly into a geographic information
system-linked database in the aircraft. The survey records the total otter numbers, the
number of dependent pups, and the number of independents (adults and subadults), observed.
These data, in conjunction with findings from several more in-depth studies provide the
necessary information to assess female reproductive rates and changes in reproductive success
of the California sea otter population through time.
The surveys, conducted cooperatively by scientists of the U.S. Geological Survey, California Department of Fish and Game, U.S. Fish and Wildlife Service and Monterey Bay Aquarium with the help of experienced volunteers, cover about 375 miles of California coast, from Half Moon Bay south to Santa Barbara. The information gathered will be used by federal and state wildlife agencies in making decisions about the management of this sea mammal. Spring survey results are used as an indicator of the population trend of California sea otters. No single year's survey result is indicative of a population change, however. To reduce the influence of anomalously high or low counts during any particular year, three-year running averages of the survey results are also used to assess whether the population is growing or declining. Factors that can influence the count include viewing conditions, abundance and species composition of surface canopy kelp, observer experience, and distribution and movements of the animals. For further information contact:Brian Hatfield USGS Western Ecological Research Center Hwy. 1, P.O. Box 70 San Simeon, CA 93452-0070 Phone: (805) 927-3893 Fax: (805) 927-3308 Email: brian_hatfield@usgs.gov Jim Estes Santa Cruz Field Station Long Marine Laboratory, UCSC 100 Shaffer Road Santa Cruz, CA 95060 Phone: (831) 459-2820 Fax: (831) 459-2249 Email: jim_estes@usgs.gov |
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