SAUSALITO, Calif.—Record numbers of distressed sea lions have washed ashore in California for a second straight year, the latest example of a marine mammal facing severe problems amid what biologists say is overfishing and other human-caused strains on the world’s oceans.
From January through May, a record 367 California sea lions have been admitted to the Marine Mammal Center here just north of San Francisco, nearly five times the average. In Southern California, more than 600 sea lions—more than twice the average—have been taken in so far this year, after a record 1,600 were treated last year.
The problem may have implications for humans, researchers say. “Sea lions are living and feeding on the same resource as humans are,” said Shawn Johnson, director of veterinary science at the Marine Mammal Center. “If they are starting to have problems, that shows there could be a problem with the ocean.”
Scientists suspect the surge in numbers has to do in part with the sea lions’ food sources moving farther away, perhaps because climate change has shifted ocean currents or changed water temperatures. Evidence suggests a problem with one of the animal’s major food sources, sardines, biologists say. The majority of the distressed animals have been pups, which biologists say likely were abandoned by their mothers for lack of food.
Some researchers suggest rising toxicity in the oceans could be playing a role as well. The number of sea lions needing help after exposure to toxins from such problems as shellfish poisoning has also risen. Federal officials are investigating the situation after declaring an unusually high sea-lion mortality rate in 2013.
Other marine mammal species around the world also have suffered health crises in recent years, due in part to human threats including overfishing, said Sam Ridgway, president of the National Marine Mammal Foundation, a nonprofit advocacy group based in San Diego.
The populations of orcas in the Pacific Northwest and beluga whales in Alaska’s Cook Inlet have both plummeted over the past two decades, amid pressures including toxic contamination and oil and gas development, according to reports by the National Oceanic and Atmospheric Administration.
Volunteers at the Marine Mammal Center in Sausalito, Calif., work to round up the mammals for feeding and medication. Preston Gannaway for The Wall Street Journal
Since 2011, about 250 Alaskan ice seals have contracted a deadly mystery ailment, while in 2012-13, about 130 manatees died and 80 bottlenose dolphins were stranded in Florida’s Indian River Lagoon system, according to NOAA reports. Although federal officials haven’t determined the causes, one possibility being explored for the ice seals is the growth of toxic algae in coastal waters from more sun exposure due to ozone depletion.
In all, the federal government has declared 38 “unusual mortality events” involving marine mammal species since 2003. That is nearly twice the number of events recorded from 1991—when the animals were put under greater federal protection—to 2002. “We still have a question whether we are seeing more because there are more, or are we seeing more because people are better trained to find a problem,” said Trevor Spradlin, a NOAA marine mammal biologist. “We don’t know yet, so time will tell.”
In some cases, federal officials have curtailed fishing to help the animals recover—at an economic cost. After Stellar sea lions were listed as threatened under the Endangered Species Act in 1990, some areas were closed to fishing for species including cod.
“You lose access to basically entire areas that were previously key to the fishery, so your production goes down,” said John Gruver, a manager for United Catcher Boats, a Seattle fleet that he estimates has lost a quarter of its cod haul as a result.
In California, sea lions are so abundant that new fishing restrictions aren’t expected anytime soon. The bigger impact is on the ability of shelters to handle the onslaught of animals. At the Marine Mammal Center overlooking the ocean here, most of the 25 holding pens were filled with mostly sea-lion pups one day last month as workers tried to care for them.
“It’s hard for us to see these starving little sea lions,” said crew supervisor Kathryn Arnold.
The pups often have to be fed a fish-gruel slurry when they first come in, and if they make it—as many as half of those rescued die—they are released back into the wild, the center’s Dr. Johnson said. He added the pups often come in weighing as little as 25 pounds; a normal weight for this time of year would be about 80. California sea lions can grow as big as 1,000 pounds.
Center officials say they are looking to add at least 100 volunteers to the 1,100 normally available and to beef up funding. Feeding the animals 1,000 pounds of fish a day costs $1,000, Dr. Johnson said.
“I thought last year’s increase was a one-time event,” he said. “I’m concerned this will be the new normal.”
If you can volunteer for the Marine Mammal Center then look into it.