California sea otter numbers were up, according to the 2013 population survey led by federal, state and university scientists. The reasons: more pups — and the addition of San Nicolas Island sea otters to the population count. The sea otters have made an impressive recovery in California since their rediscovery in the 1930s. But as their numbers expand along California's coast, they are facing different 'growing pains' in different locales.

Since the 1980s, U.S. Geological Survey (USGS) scientists have calculated an averaged population index each year for the Southern sea otter — Enhydra lutris nereis — a federally listed threatened species found in California. For the 2013 report, USGS lists the population index as 2,941. For southern sea otters to be considered for removal from threatened species listing, the population index would have to exceed 3,090 for three consecutive years, according to the threshold established under the Southern Sea Otter Recovery Plan by the U.S. Fish and Wildlife Service. Population growth in central California has faltered recently, so this slightly positive trend was a basis for cautious optimism

They counted a record number of pups in 2013, which led to the uptick in the 3-year average. A high pup count is always encouraging, although the number of adult otters counted along the mainland was almost identical to last year's count, so it was a wait and see if the positive trend continued. Part of the reason for the higher population index reported in 2013 was the addition of sea otters living at San Nicolas Island, a former experimental population when one-hundred-and-forty sea otters were introduced to the island in the 1980s as part of a USFWS recovery experiment. This programme has been terminated in 2012, and as a consequence, sea otters at San Nicolas Island became part of the California-wide population index for southern sea otter recovery. The population at the island was 59 individuals in 2013.

In 2018 the 3-year average of combined counts from the mainland range and San Nicolas Island was 3,128, a decrease of 58 sea otters from the previous year. Nevertheless a higher count than in 2013.

The USGS completed the annual rangewide southern sea otter census survey for 2024 (no numbers available yet), but has started also developing a new statistical model designed to provide more accurate estimates of the southern sea otter population in California.

Various video footage (date: 30.06.2008) of sea otter researchers, show this threatened but resilient species in its scenic habitat in California, USA.

(Credit: U.S. Geological Survey; video published in the public domain.)