SANTA BARBARA, Calif. (AP) — Sea lions are stranding themselves on a long stretch of the California coast and showing signs that they may have been poisoned by a bloom of harmful algae, experts said Thursday.

The Channel Islands Marine & Wildlife Institute said that since July 26, it has been inundated by daily reports of sick sea lions along 155 miles (249 kilometers) of shoreline in Santa Barbara and Ventura counties, northwest of Los Angeles.

The marine mammals are suffering from domoic acid, a neurotoxin that affects the brain and heart, the institute said in a statement. The poisoning event is largely affecting adult female California sea lions, it said.

The nonprofit said it had rescued 23 animals so far. Coastal Vandenberg Space Force Base released photos of sea lions being rescued from one of its beaches on July 29.

The California coast commonly sees outbreaks of domoic acid poisoning, according to the National Oceanic and Atmospheric Administration’s NOAA Fisheries.

An outbreak last year was particularly severe, with hundreds sea lions and dozens of dolphins dying in the first weeks of June.

The poison is produced by microscopic algae that are consumed by shellfish and small fish that are then eaten by sea lions, dolphins and birds. Symptoms in affected sea lions may include disorientation, head weaving, foaming at the mouth and seizures.

People can also get sickened.