Tainted Catch

Divers take note — if you’re in Mission Bay, La Jolla, or anywhere else along the California coast, don’t move a mussel. Or, to be more specific, don’t harvest and eat a mussel.

A quarantine on the recreational harvesting of all mussel species was issued at the beginning of May by the California Department of Public Health and will be in effect through October 31.

Eating affected mussels could cause paralytic shellfish poisoning (PSP) or domoic acid poisoning (DAP). According to Melissa Carter, a researcher at Scripps Institution of Oceanography, she and her colleagues found domoic acid in seawater samples collected from Scripps Pier between April 20 and May 5. She notes that it was “at fairly low concentrations.”

Domoic acid is a naturally occurring marine toxin found in various species of algae. Although it can accumulate in fish and shellfish in high concentrations without apparent harm, the substance acts as a potent neurotoxin to humans.

Carter says that the researchers from Scripps routinely send mussels to the California Department of Health to test for domoic acid and paralytic shellfish poisoning toxins. Though testing can reveal if certain geographic areas of shellfish are affected, sport divers and recreational harvesters may be unaware that their catch is tainted.

“If a person were to go out today and harvest a bunch of mussels, they would most likely go straight home and prepare them to eat the same day or within a few days,” says Carter, “They would not know if the shellfish were safe to eat unless they waited for the results from the marine biotoxin monitoring program.”

When affected shellfish are ingested, symptoms of domoic acid poisoning range from vomiting and diarrhea to memory loss, seizures, and, in rare cases, death. Paralytic shellfish poisoning can cause symptoms ranging from disturbed balance and a tingling around the mouth to complete muscular paralysis, asphyxiation, and death. The quarantine does not affect commercially sold mussels, which are bound by strict regulations for testing before harvesting.