From the California Department of Public Health:
Dangerous levels of domoic acid have been detected in mussels from Humboldt and Mendocino Counties. The naturally occurring toxin is also referred to as Amnesic Shellfish Poisoning (ASP) and can cause illness or death in humans. Cooking does not destroy the toxin.
The California Department of Public Health (CDPH) is advising consumers not to eat sports-harvested mussels, clams, or whole scallops from those counties.
This shellfish safety notification is in addition to the annual mussel quarantine. The annual quarantine applies to all species of mussels harvested along the California coast, as well as all bays and estuaries, and will continue through at least October 31. The warning against eating sport-harvested razor clams in Del Norte and Humboldt counties also remains in effect, due to continued elevated levels of domoic acid.
This warning does not apply to commercially sold clams, mussels, scallops or oysters from approved sources. State law permits only state-certified commercial shellfish harvesters or dealers to sell these products. Shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing to monitor for toxins.
Symptoms of ASP can occur within 30 minutes to 24 hours after eating toxic seafood. In mild cases, symptoms may include vomiting, diarrhea, abdominal cramps, headache and dizziness. These symptoms disappear within several days. In severe cases, the victim may experience trouble breathing, confusion, disorientation, cardiovascular instability, seizures, excessive bronchial secretions, permanent loss of short-term memory, coma or death. No cases of human ASP from domoic acid are known to have occurred in California.
You can get the most current information on shellfish advisories and quarantines by calling CDPH’s toll-free Shellfish Information Line at (800) 553-4133. For additional information, please visit the CDPH Marine Biotoxin Monitoring Web page.