California’s Sea Otter Numbers Holding Steady
U.S. Geological Survey has just released the Spring 2014 California Sea Otter Census Results. The official range-wide southern sea otter abundance index, calculated from both the California mainland range and San Nicolas Island population, is 2,944. The 5-year average growth rate for the overall population is 0.7%. For more info, check out this USGS blog post.
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 and what threshold has to be met for the species to be “delisted.”
For more info, check out http://www.werc.usgs.gov/seaottercount.