The California Department of Public Health (CDPH) has lifted the shellfish safety notification today related to sport-harvested mussels, scallops, and most types of clams from Humboldt County. An advisory for razor clams in Humboldt County remains in effect. CDPH has also lifted the shellfish safety notification related to sport-harvested mussels, scallops, and clams from Sonoma County.
The safety notifications for Humboldt County issued July 3, 2024, and Sonoma County issued July 19, 2024, were due to dangerous levels of naturally occurring paralytic shellfish poisoning (PSP) toxins. The safety notification for Humboldt County issued August 9, 2024, was due to dangerous levels of naturally occurring domoic acid, also referred to as amnesic shellfish poisoning. Both of these biotoxins can cause illness or death in humans. Recent testing shows the biotoxins have decreased to safe or undetectable levels for bivalve shellfish in these areas, except razor clams in Humboldt County.
This notification does not change the annual mussel quarantine, which still remains in effect. The annual quarantine prohibits the sport-harvest of mussels for human consumption and 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.
A warning against eating sport-harvested razor clams from Humboldt County remains in effect as razor clams are a high risk for long-term elevated levels of domoic acid. Razor clams are known to retain domoic acid toxin in their meat and tissues much longer than other species of bivalve shellfish.
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 amnesic shellfish poisoning 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.
PSP toxins affect the nervous system, producing a tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms are typically followed by loss of balance, lack of muscular coordination, slurred speech, and difficulty swallowing. In severe poisonings, complete muscular paralysis and death from asphyxiation can occur.
The original press release from CDPH is posted here.
