A recent spike in sick California sea lions along the Central Coast is beginning to ease, but marine wildlife experts say the threat is far from over.
Officials with The Marine Mammal Center say they responded to about 13 sea lions in San Luis Obispo County showing signs of domoic acid poisoning in late March and early April.
Cases have tapered off in recent weeks, but experts warn conditions could lead to additional sea lion strandings.
“It’s become a lot more unpredictable,” said Aliah Meza, senior manager of the Center’s San Luis Obispo operations. “We used to see these outbreaks mostly in the summertime, but now we’re seeing cases in the spring and even into the fall.”
Domoic acid is a neurotoxin produced by algal blooms linked to Pseudo-nitzschia australis – a Harmful Micro Algae which is currently present at high levels along the Central Coast and down to the Channel Islands.
The toxin builds up in small fish like anchovies and sardines. When sea lions consume those contaminated fish, it can attack their nervous systems, causing symptoms like disorientation, seizures and abnormal behavior.
Experts are also closely monitoring warming ocean conditions tied to El Niño and broader climate change, which can disrupt the marine food web. Meza says these conditions can push prey farther offshore and lead to malnourished sea lions and pups.
“Fish end up swim[ming] off more offshore. They also go into deeper waters where it's cooler,” Meza said. “And what that can lead to is these sea lions then have longer foraging trips.”
Those longer trips can take a toll, Meza said. Especially on pregnant females that need consistent nutrition to support themselves and their developing pups. She explains that during past warming events, similar conditions contributed to malnutrition and increased strandings.
Officials are urging the public to stay at least 50 feet away from stranded marine mammals and to report sightings to trained responders rather than intervening.
