California sea lions face surge in domoic acid poisoning

California's coastal waters are experiencing a severe outbreak of domoic acid poisoning, leading to a surge in sickened sea lions. The Marine Mammal Center in Sausalito reports rescuing more than 150 sea lions so far this year, which is more than double its typical annual total.

The neurotoxin is produced by naturally occurring harmful algal blooms. It enters the food chain when fish consume the algae, subsequently poisoning larger predators like sea lions that eat the contaminated fish. Symptoms in affected animals include lethargy, muscle twitching, seizures, and brain lesions. One sea lion recently died at San Francisco’s Crissy Field after displaying head-weaving and bobbing behaviors.

Environmental scientists, including UC Santa Cruz professor Dan Costa, suggest that warming ocean temperatures associated with El Niño may be contributing to the intensity of these blooms. Public health officials continue to monitor seafood safety, as consuming contaminated fish can cause severe illness or death in humans.