Wildlife rescuers report an increase in the number of sick sea lions along California’s central coast.
The culprit is domoic acid, a neurotoxin produced by harmful algal blooms.
The toxin accumulates in filter-feeding fish such as sardines and anchovies, which are consumed in large quantities by sea lions, dolphins and fur seals.
Sausalito Marine Mammal Center spokesman Giancarlo Rulli said the center’s network has seen an increase in the number of affected sea lions along the coasts of Santa Barbara and San Luis Obispo counties since mid-July. He said rescuers had rescued more than 70 sea lions, two dolphins and two fur seals.
Rulley said about 25 percent of sea lions eventually die — either from disease or “humane euthanasia.” Dolphins and fur seals also died.
He said by the time staff found the two dolphins, they had taken over the beach.
“Once they’re out of the water, you’re in a race against time,” he said of the larger mammals. While sea lions often leave the water, a dolphin’s own weight can crush its organs if it stays on dry land for too long.
It’s a tragic situation and “euthanasia is often the first and first” response to relieve suffering, “especially when a dolphin is having a seizure,” Ruley said.
Staff at the Channel Islands Marine and Wildlife Research Institute have also been fielded with numerous calls about sick animals.
As of Friday, the institute was receiving about 100 reports a day of sick sea lions in Ventura and Santa Barbara counties. Wildlife Rescue President Samuel Dover said staff had rescued 23 animals as of Thursday.
“There are many more deaths,” he said.
Domoic acid attacks the brain and heart, causing seizures and heart failure. If left untreated, permanent brain damage often results. The toxins are naturally eliminated from the animal’s system over time, but repeated exposure may cause longer-lasting and more severe effects.
Ruley said the behavior of affected animals can be “across the board: lethargy, disorientation, classic dizziness…the classic signs that there may be neurological problems associated with domoic acid poisoning.”
Dover of the Channel Islands Research Institute said this year’s algal bloom mainly affected adult female sea lions.
In similar incidents last year and in 2022, the poisonings did not appear to discriminate based on gender or age.
“But it’s still early,” Dover said.
He said the epidemic will last 27 days in 2023, down from 37 days in 2022.
Ruley said those outbreaks occurred further south.
He said saving the animals could be difficult given their size. Adult female sea lions can weigh up to 250 pounds, and adult males can weigh up to 1,000 pounds. He said it would take a crew of four to six people to rescue an adult female, meaning resources were stretched.
If the animal can be triaged and stabilized nearby, rescuers will try to transport it to the institute’s hospital in Sausalito, Ruley said.
Both Ruley and Dover warned people to give sick animals plenty of space on their beaches.
NOAA urges beachgoers to stay at least 50 yards (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 a marine animal they think may be sick should call a nearby wildlife rehabilitation specialist, such as those at the Marine Mammal Center in Sausalito at (415) 289-7325 or the Channel Islands Marine and Wildlife Institute Experts at (805) 567-1505.
