Wildlife rescuers are reporting an increase in the number of sick sea lions along California’s central coast.
The culprit: domoic acid, a neurotoxin produced by harmful algal blooms.
The toxin accumulates in filter-feeding fish such as sardines and anchovies, which are eaten in large quantities by sea lions, dolphins and fur seals.
Giancarlo Rulli, a spokesman for the Marine Mammal Center in Sausalito, said that since mid-July, the center’s network has seen an increase in the number of sea lions being affected along the coast in Santa Barbara and San Luis Obispo counties. He said rescuers have responded to calls for more than 70 sea lions, as well as two dolphins and two fur seals.
According to Rulli, about 25 percent of these sea lions died, either from disease or from “humane euthanasia.” Dolphins and fur seals also died.
By the time staff reached the two dolphins, he said, they were convulsing on the beach.
“Once they’re out of the water, it’s a race against time,” he said of the large mammals. While sea lions often spend time out of the water, if a dolphin is on land for long periods of time, its own weight will crush its organs.
Rulli said this was one of those tragic situations where “euthanasia is often the primary and No. 1 response” to alleviate suffering, “especially when dolphins are having seizures.”
Staff at the Channel Islands Marine & Wildlife Institute have also received numerous calls regarding sick animals.
As of Friday, the institute was receiving about 100 reports a day of sick sea lions in Ventura and Santa Barbara counties. By Thursday, teams had rescued 23 animals, said Samuel Dover, president of the wildlife rescue organization.
“There were many more deaths,” he said.
Domoic acid attacks the brain and heart, causing seizures and heart failure. If left untreated, it usually causes permanent brain damage. The toxin is naturally eliminated from the animal’s system over time, but repeated exposure can cause longer-lasting and more serious effects.
Rulli said the behavior of an affected animal can be “very varied: lethargy, disorientation, classic head bobbing … the classic telltale signs that there is probably a neurological problem associated with domoic acid poisoning.”
Dover, of the Channel Islands Institute, said this year’s algal bloom is primarily affecting adult female sea lions.
In similar events last year and in 2022, poisoning did not appear to discriminate based on gender or age.
“But it’s still early,” said Dover, who noted that while there were some reports as early as June, incidents of sick animals didn’t really pick up again until late July.
He said the 2023 outbreak lasted 27 days, compared to 37 in 2022.
Rulli said these outbreaks occurred further south.
It can be difficult to rescue the animals because of their size, he said. An adult female sea lion can weigh up to 250 pounds and a male can weigh up to 1,000 pounds. It takes several people, four to six, to rescue an adult female, meaning resources are limited.
If the animal can be triaged nearby and stabilized, Rulli said, rescuers will try to transport it to the institute’s hospital in Sausalito.
Rulli and Dover both recommended that people give sick animals plenty of space on the beach.
The National Oceanic and Atmospheric Administration urges beachgoers to stay at least 50 yards, or about half a football field, away from seals and sea lions, whether the animals are sick or healthy, and to keep pets away.
Those who see marine animals they believe to be sick should call nearby wildlife rehabilitation experts, such as those at the Sausalito Marine Mammal Center, (415) 289-7325, or the Channel Islands Marine & Wildlife Institute, (805) 567-1505.
