A rise in marine mammal deaths linked to domoic acid in the waters off some areas of Southern California

SANTA BARBARA COUNTY, Calif. -  The number of sightings of dead or sick animals along the Central Coast are up in the last few weeks and the cause is believed to be the rise in domoic acid in the ocean.

The Common dolphin and California sea lion populations are the most impacted along with shore birds like pelicans.

Studies show sea lions are regularly found with dolphins year-round and search for food in similar places.

Dead dolphins in the last week have been found in Ventura County, Santa Claus Beach, Hammonds long the Montecito coast and near Stearns Wharf.

The Channel Islands Marine and Wildlife Institute (CIMWI) says the domoic acid poisoning is linked to a, "harmful algal bloom events by a certain type of algae, Pseudo-nitzschia australis. This neurotoxin accumulates in shellfish as well as small fish like sardines and anchovies. When sea lions and other animals eat the contaminated fish with the toxin, it can be extremely harmful and even fatal when consumed in sufficient quantities."

This is the forth year for the algal bloom which used to be more of a Spring event. 

In recent years, it has also occurred around August, September, and October.

The recent wildfires and the subsequent runoff of ash and burnt materials along with an ingredient in the fire retardant used may also be a contributing factor according to CIMWI.

The public is asked to contact the marine mammal hotline if they are concerned about a sick or deceased marine mammal or shorebird and CIMWI will try to respond. 

It is a volunteer organization run off donations.

According to CIMWI:

• Current DA Event (2025):
  • Event started on February 19, 2025
  • Through 3/16/25 (day 25):
    • CIMWI is currently managing 150 reports a day about animals in distress, the majority of these reports are about sea lions and dolphins exhibiting signs of domoic acid posioning
    • CIMWI has responded to 148 marine mammals reported as exhibiting signs of domoic acid poisoning
      • Majority have been adult female California sea lions and many of those were pregnant (birthing is June-July with peak 6/15)
    • 20% of the animals were dead upon arrival or died during response/rescue effort
    • The majority of the live animals CIMWI has responded to were put under observation initially
    • CIMWI has rescued 10 animals suffering from domoic acid poisoning
    • There have been 25 dolphin strandings (24 either stranded dead or died shortly after stranding on the beach, 1 was rescued and died shortly after rescue effort)

For more information contact: CIMWI or the Santa Barbara Wildlife Care Network