Mysterious Sea Lion Decline Persists In Western Alaska

Dec 7, 2016

One month old Steller sea lion pups playing on Ulak Island.
Credit Courtesy NOAA Fisheries

Alaska’s endangered Steller sea lion population continues its precipitous decline. The 2016 survey by the National Oceanic and Atmospheric Administration (NOAA) shows an overall increase in the number of Steller sea lions across Alaska, but a mysterious drop in parts of the western stock.

The big takeaway from this year’s Steller sea lion survey is this: the farther west you go, the worse it looks for Stellers. At the end of the Aleutian chain, the population is dropping about 7 percent a year.

Lowell Fritz is a biologist with NOAA. He says the outlook for the western stock is bleak.

“The probability of extinction for that western Aleutian population is greater than 50 percent within 50 years,” Fritz said. “We’re down to less than 200 pups produced a year in an area that used to produce thousands. It’s gone down 95 percent since the late 70s.”

Steller sea lions on Akutan.
Credit Courtesy NOAA Fisheries

For nearly 40 years, the western stock has been declining, hitting a low in 2002. But scientists like Fritz are having a hard time pinpointing the cause.

“We don’t see a mass exodus of animals that we’ve marked and tagged from these western Aleutian or central Aleutian areas that are declining,” he said.

One reason may be the western stocks aren’t having as many pups or the pups they do have aren’t getting to breeding age so they can have pups of their own. But without identifying a culprit for the decline, there are poor prospects for the species.

Even though the eastern stock of Stellers is doing better, Fritz says it’s important to maintain populations throughout the animal’s range to reduce the threat of extinction.