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.
The stranding team is part of the West Coast Marine Mammal Stranding Network coordinated by NOAA Fisheries. The Network relies on the public to report stranded marine mammals to the Stranding Hotline at (866) 767-6114. Entangled animals can be reported to (877) 767-9425, while harassment of marine mammals and other violations should be reported to NOAA’s Office of Law Enforcement at (800) 853-1964. Beachgoers should remain a safe distance (a minimum of 50 yards) from affected animals—they can act erratically under the influence of the biotoxin.
The rising number of strandings in recent days demonstrates the importance of Stranding Hotline and Stranding Network partners, including San Diego county lifeguards, California State Park officers, and biologists from the U.S. Navy. Toxicologists at NOAA Fisheries’ Northwest Fisheries Science Center analyze the biological samples.
