LOS ANGELES — Scientists are looking at ocean-warming trends to figure out why endangered Guadalupe fur seals are stranding themselves and dying in alarming numbers along the central California coast.
Approximately 80 emaciated fur seals have come ashore since January — about eight times more than normal — leading the National Oceanic and Atmospheric Administration this week to declare an “unusual mortality event” for the animals.
The classification diverts additional resources to study the animals, which have been traditionally under-researched, officials said.
Researchers will try to determine if the die-off is a result of a disruption in the seal’s feeding patterns from a large-scale warming of the Pacific Ocean, Toby Garfield, an official with NOAA’s Southwest Fisheries Science Center, said Tuesday.
The so-called warm blobs occurring during a persistent high-pressure ridge have grown to cover most of the West Coast and have been previously blamed for discoveries of emaciated young sea lions off California and starving seabirds off Oregon and Washington.
Some of the fish species that fur seals usually eat may have moved farther north to escape the unusually warm waters, Garfield said during a teleconference.
“We think that warm water conditions have really changed the range of quite a few of the forage fish species that the fur seals would be going after,” he said.
Garfield expects the high-pressure system to persist for a few more months, when El Nino, another ocean-warming phenomenon, could cause further problems.
Of the 80 Guadalupe sea lions stranded so far this year, 42 were found dead, said Justin Viezbicke, a NOAA coordinator in Long Beach.
From 2009 through 2014, the agency recorded only about 10 strandings per year.
The spike “demands immediate response,” resulting in the designation, Viezbicke said.
The majority of the stranded seals were pups born last year, but at least 4 were adult females, said Tenaya Norris, a scientist at the Marine Mammal Center in Sausalito, where most of the animals were rehabilitated.
The center has responded to stranded fur seals since 1977, and before 2015, the highest number it has admitted in any other year is five, Norris said. SeaWorld in San Diego nursed other emaciated seals back to health.
Guadalupe fur seals breed almost entirely on Guadalupe Island near Baja California, Mexico, more than 600 miles from where they are stranding in central California.
Male fur seals can grow up to 7 feet long and top out at around 400 pounds.
Hunting brought the species to near extinction in the late 1800s.
It had been slowly recovering.
The seal has been listed as threatened under the Endangered Species Act since 1967 and also is protected by the Marine Mammal Protection Act.
The current population is estimated at more than 10,000 animals.
An unusual mortality event was declared in 2007 for Guadalupe fur seals in Oregon and Washington, according to NOAA.