Scientists raise alarm over large number of Guadalupe fur seal deaths off California coast

In a year that has proven challenging for a variety of marine mammal species commonly seen off the California coast, federal wildlife officials on Tuesday declared that an alarming eight-month die-off of Guadalupe fur seals calls for more in-depth study and investigation.

The Guadalupe fur seal - already a threatened species under the Endangered Species Act - appears to be experiencing sharp new challenges finding food, problems similar to those that have caused several thousand emaciated California sea lions, most of them pups, to come ashore over the past year, according to representatives from the National Oceanic and Atmospheric Administration.

About 80 Guadalupe fur seals have been found on the shore since January, a figure that’s eight times the annual average, NOAA stranding coordinator Justin Viezbicke said. Most of the animals were found on the Central Coast. Eight were found on the North Coast, including two in Sonoma County, one each in Mendocino and Marin counties and four in Humboldt County, according to marine mammal rescuers.

Since the fur seals typically forage far offshore for long periods of time - unlike sea lions, which hunt near shore and haul out periodically - the strandings are a dire sign of trend that is probably worse than currently known, experts said.

“That is a pretty big warning sign that we need to pay attention,” Tenaya Norris, a scientist with The Marine Mammal Center in Sausalito, said during a conference call with reporters Tuesday.

Scientists suspect a band of warm water off the western United States is driving squid and other forage fish north, forcing certain marine mammals and their young to travel farther to feed. Many are starving in the meantime, making the animals vulnerable to opportunistic infection and other problems.

“We think that warm water condition has really changed the range of a lot of the forage fish species that the fur seals would be going after,” said Toby Garfield, director of the environmental research division for NOAA Southwest Fisheries Science Center.

The known strandings include 42 fur seals that were found dead and 38 found alive, Viezbicke said.

Of 33 taken to The Marine Mammal Center for treatment, 11 survived through rehabilitation to release, Norris said. The remainder died or were euthanized. All but four were pups born last winter.

Tracking instruments placed on those returned to the wild this year indicated they traveled farther north than usual after their release, she said. At least five swam all the way to Vancouver Island in northern Washington before their tags stopped transmitting, Norris said. Rehabilitated fur seals released in the past have typically remained south of Cape Mendocino, she said.

Guadalupe fur seals were heavily hunted in the 18th and 19th centuries and were thought to be extinct in the early 1900s, according to NOAA Fisheries. Their population is recovering slowly and is now believed to number just above 10,000.

Though a poorly studied species, they are known to breed almost exclusively on Guadalupe Island off the coast of Mexico, though smaller populations have been linked to San Benito Island off of Baja California and on San Miguel Island off of Southern California.

You can reach Staff Writer Mary Callahan at 521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.