Poisoned sea lions wash ashore along California coast

Thursday 03 September 2026 - 19:00

By: Azzat Manal

Poisoned sea lions wash ashore along California coast

Dozens of sick and disoriented sea lions have washed up on California beaches in recent days, prompting wildlife authorities and marine experts to warn the public against approaching the affected animals.

The Marine Mammal Center said the animals are suffering from domoic acid poisoning, a neurological illness caused by a toxin produced by certain marine algae. The toxin can enter the food chain when fish such as sardines and anchovies consume toxic algae before being eaten by sea lions.

Domoic acid can affect areas of the brain responsible for memory and behavior, causing seizures, tremors, abnormal movements, confusion and lethargy. In severe cases, the poisoning can be fatal.

Dozens of affected sea lions were reported during the final week of August around the San Francisco Bay Area. Since the beginning of 2026, more than 100 cases of sick sea lions have been recorded in the United States, compared with an average of between 70 and 90 cases annually.

Recent cases have been concentrated around the Monterey Peninsula and nearby stretches of California’s central coast, particularly in Monterey and Santa Cruz counties. Reports of domoic acid poisoning began earlier in the summer but increased significantly toward the end of August, raising questions among researchers about the delayed surge.

The phenomenon is associated with blooms of algae, including species of the genus Pseudo-nitzschia, which can produce domoic acid under certain ocean conditions. Strong coastal winds can drive nutrient-rich, cold water toward the surface, creating favorable conditions for toxic algae to multiply and spread through the marine food web.

Michael Milstein, a spokesperson for the National Oceanic and Atmospheric Administration, said such events can occur during colder-water years when strong upwelling brings nutrients toward the surface, but they can also develop during warmer periods. Scientists are also examining whether changes in Pacific Ocean temperatures and El Niño conditions could contribute to increased toxic algal activity.

Domoic acid is not only a threat to marine wildlife. Humans can also be exposed by consuming contaminated seafood, including mussels, clams, crab viscera, sardines and anchovies. The toxin is not eliminated through normal cooking or freezing, and high levels of exposure can be potentially fatal.

Wildlife experts have documented cases in which affected sea lions became aggressive toward humans during previous poisoning events. However, simply touching a sick animal does not cause domoic acid poisoning, and a sea lion bite is not considered the usual route of exposure. The Marine Mammal Center has nevertheless urged people to keep their distance and allow trained responders to handle affected animals.

California’s coastline is home to an estimated 250,000 sea lions, compared with around 1,500 in the 1920s. The growing population makes monitoring disease and toxin-related events increasingly important for both wildlife conservation and public safety.

The latest outbreak highlights the complex links between ocean conditions, toxic algae and marine ecosystems, while giving researchers another opportunity to study how environmental changes may influence harmful algal blooms along the California coast.