California Sea Otter Surveys: Every Otter Counts
Every spring and fall, scientists and volunteers fan out across 400 miles of California coastline to count sea otters. Utilizing shore-based and aerial observations, survey teams use binoculars and spotting scopes to count individual animals from accessible stretches of coastline and from fixed-wing aircraft in the remaining areas. Each survey records the total number of sea otters, the number of dependent pups, and the number of independents (adults and subadults) observed. These counts provide a critical measure of the current overall status of the population.
Population trends (assessing whether the population is growing or declining) for the southern sea otter are monitored using a 3-year running average of the spring sea otter survey. So for example, values for 2010 are based on the averages of the 2009, 2010, and 2011 spring surveys. The 3-year running average is also used to determine the species’ official listing status under the Endangered Species Act (ESA) and what threshold has to be met for the species to be “delisted.” California’s southern sea otter has been listed as a ‘threatened ‘species under the ESA since 1977.
The 2012 California Sea Otter Survey released today by the U.S. Geological Survey shows the population may be at a plateau, with yet a long road to recovery.