Monterey County sees a surge in California sea lions sickened with domoic acid.

Monterey Bay has seen an uptick in California sea lions sickened with domoic acid poisoning, a neurotoxin that causes the marine mammal to exhibit erratic behaviors that include unusual head bobbing, twitching, disorientation and seizures.

The Marine Mammal Center in Castroville has been serving as the triage center for which to handle these animals, most of which are subadults and adult California sea lions weighing anywhere from 125 to more than 300 pounds.

“We’re getting anywhere from 300-600 calls to our hotline every single day,” says Giancarlo Rulli, spokesperson for the nonprofit. He adds that it takes anywhere from four to six volunteers to respond to each sea lion.

Domoic acid is a neurotoxin produced by blooms of the algae Pseudo-nitzschia. In June, the state’s Department of Fish and Wildlife issued a health advisory after detecting high levels of the neurotoxin in Monterey Bay fish.

Rulli says that although the cases of sickened sea lions have been relatively spread out, it has been most pronounced in Monterey County. Cases have largely been reported in Pajaro Dunes State Beach, Seaside and Del Monte beach, “mainly south of Watsonville,” Rulli says.

While domoic acid is often associated with warmer water temperatures, Rulli says this is a misnomer, and that domoic acid toxicosis has been seen throughout the year and can thrive in both cold and warm conditions.

“What has changed is that this neurotoxin has become more unpredictable and less seasonal than what we discovered back in 1998,” Rulli says. “Outbreaks trend more intense and more unpredictable.”