Wednesday April 23, 2025
NOAA Fisheries —
The stranding team from NOAA Fisheries’ Southwest Fisheries Science Center recovered 16 dead dolphins from San Diego beaches on Sunday, April 20. These deaths add to the likely toll of a domoic acid outbreak produced by a harmful algae bloom off Southern California. Most of the dolphins were already dead when responders arrived, or died shortly afterwards. None survived long enough for treatment. Most were adult male long-beaked common dolphins with a few short-beaked common dolphins. Two were pregnant females.
The Sunday toll brings the total dolphins collected by the San Diego team since the first impacts of the domoic acid event were seen in March to more than 50. The details provide a snapshot of how the ongoing harmful algal bloom is affecting one of the most popular stretches of the Southern California coastline. Of the 14 dolphins tested so far, 11 have had high levels of domoic acid. One showed both domoic acid and saxitoxin, a different neurotoxin produced by another marine microorganism that causes paralytic shellfish poisoning.
Hundreds of additional dolphins and sea lions have also died in other areas of California since the first domoic acid impacts were detected near Los Angeles in February. This is the fourth consecutive year with a harmful algal bloom off Southern California; the current bloom began earlier in the year than prior blooms. The Southern California Coastal Ocean Observing System monitors domoic acid levels off Southern California, and displays domoic acid forecasts online. The impacts are not likely to affect California dolphins or sea lions at a population scale. NOAA Fisheries’ most recent stock assessment report suggests a population estimate of more than 80,000 long-beaked common dolphins, while short-beaked common dolphins were estimated at more than 1 million. Biologists also estimate that about 250,000 California sea lions live along the coast.