As go sea otters, so goes our nearshore marine ecosystem. This staggering decline in their population after years of growth is concerning, and signals that it is too early to declare the sea otter fully recovered.
For Immediate Release
Survey Reveals Southern Sea Otter Population Decline
The southern sea otter population dropped in the last year, according to the United States Geological Survey (USGS) 2017 spring survey published Friday. The results are especially alarming following an overall positive growth through 2016, which culminated in a population size that – if maintained for three consecutive years – could have led to southern sea otters being delisted under the Endangered Species Act (ESA).
While the U.S. Fish and Wildlife Service (FWS) noted only a 3 percent decline in sea otter numbers, their statement fails to tell the whole story. The FWS was correct in that the three-year average reflects only a 3 percent decline, but they did not note that the raw numbers of sea otters counted during the spring survey declined by 927 sea otters between the mainland and San Nicolas Island – an over 25 percent decline from the raw numbers of sea otters counted last year.
Friends of the Sea Otter issued this statement:
“This dramatic decline in the sea otter population raw count calls into question our optimism over the potential recovery of this species, and is a wake-up call to redouble our efforts to understand this downward trend and to save these important and beautiful creatures."
Emily Burke, California program assistant for Defenders of Wildlife, issued this statement:
“As go sea otters, so goes our nearshore marine ecosystem. This staggering decline in their population after years of growth is concerning, and signals that it is too early to declare the sea otter fully recovered.”
The 2017 USGS southern sea otter survey results showed the raw count population size dropped to 2,688 an over 25 percent decline from last year. The 2016 survey recorded a raw count population size of 3,615, the highest survey result ever. The decline in population survey results is the largest numerical and percentage decline in consecutive years since the annual survey began in 1985.
The causes of population decline unfortunately remain uncertain. One likely factor is the increased incidence of attacks by white sharks on sea otters at the southern end of the sea otter range. While scientists are unable to confirm why the rate of shark attacks has increased, it could be the result of sharks spending more time in nearshore waters because of the recent increase in their primary prey, pinnipeds like northern elephant seals.
Additionally, shifts in ocean current patterns due to climate change may be changing the distribution of marine ecosystem food chains. With a thick fur coat and no blubber layer, sea otters are not a traditional source of prey for sharks. While sea otters have always been mistaken for traditional prey sources and attacked, the substantial increase in shark attacks is likely an artifact of changes in shark distribution patterns. Other factors in the sea otter decline may include a decrease in the number of sea urchins—one of sea otters’ preferred prey items—following a few years of relatively large urchin populations, as well as compromised water quality in the nearshore environment due to pollution and agricultural runoff.
FSO and Defenders of Wildlife maintain that regardless if the population exceeds 3,090 for three consecutive years, the sea otter is unlikely to meet the full criteria for delisting and recovery under the ESA. The 2017 spring survey results reinforce FSO’s and Defenders of Wildlife’s position that additional range expansion and healthy and sustained population size significantly above the recovery threshold of 3,090 are necessary for the population to be considered for a recovery determination.
The magnitude of the population decline emphasizes the importance of providing full protection of sea otters under the ESA and the Marine Mammal Protection Act. In addition, FSO and Defenders of Wildlife encourage the public to avoid engaging in activities that could result in harassment or harmful interactions with sea otters. For additional information regarding appropriate sea otter viewing guidelines, please refer to the Sea Otter Savvy program at www.seaottersavvy.org.
Defenders of Wildlife is dedicated to the protection of all native animals and plants in their natural communities. With over 1.8 million members and activists, Defenders of Wildlife is a leading advocate for innovative solutions to safeguard our wildlife heritage for generations to come. For more information, visit Newsroom.Defenders.org and follow us on Twitter @DefendersNews.