When sea otters want to rest, they wrap a piece of kelp around their body to hold themselves steady among the rolling waves. Lik
ewise, California’s sea otter numbers are holding steady against the many forces pushing against their population recovery, according to the latest field survey led by federal, state, aquarium, and university scientists.
Since the 1980s, U.S. Geological Survey scientists have calculated a population index each year for the southern sea otter—Enhydra lutris nereis—a species federally listed as Threatened. The annual range-wide field survey collects data on this protected marine mammal on behalf of the U.S. Fish and Wildlife Service.
For 2014, USGS reports the population index as 2,944 (data available online). It’s a negligible bump from the 2013 report of 2,939.
For southern sea otters to be considered for removal from the “Threatened” species list, the population index would have to exceed 3,090 for three consecutive years, according to the Southern Sea Otter Recovery Plan established by the U.S. Fish and Wildlife Service.
“For an animal so few in number, sea otter population trends can be influenced by many local and range-wide factors,” says biologist Tim Tinker with the USGS Western Ecological Research Center, who leads California sea otter research with co-investigators from the California Department of Fish and Wildlife’s Office of Spill Prevention and Response, the Monterey Bay Aquarium, University of California, Santa Cruz, and other institutions. “We are seeing elevated mortality suggestive of food resource limitation in some parts of the range, and increasing mortality from white shark attacks in others. But our federal, state, aquarium, and university sea otter research alliance is making progress in understanding how all these trends relate to environmental factors along the California coast.”
California sea otters feed and live in the “near shore marine ecosystem”—the stretch of ocean that hugs a shoreline—making them a good indicator species for detecting pollutants and pathogens1 washed down from coastlands. And along many parts of Pacific North America, sea otters play critical roles in natural food webs, keeping important ecosystems like kelp forests and seagrass beds in balance.
Studying sea otters, then, not only helps us understand their population recovery, but it also uncovers clues on the health and rhythm of near shore marine ecosystems—the same waters many people swim, fish, and make a living in every day.
1pathogens: a germ (as a bacterium or virus) that causes disease
Which word describes the effort to document sea otter populations in California, based on this article?
Collaborative
Competitive
Desolate
Frustrating
