Welcome to the State of California 


Date: 5/8/2009 

Number: 09-41 

Contact: Al Lundeen or Ronald Owens - (916) 440-7259 


The annual quarantine of all mussel species harvested by the public on California’s coasts, bays and estuaries became effective May 1 and continues through October 31.

The statewide mussel quarantine is intended to prevent human cases of paralytic shellfish poisoning (PSP) and domoic acid poisoning (DAP).  The quarantine applies only to sport-harvested mussels.

Paralytic shellfish poisoning (PSP) is a form of nervous system poisoning.  Concentrated levels of the PSP toxins can develop in California mussels and other bivalve shellfish when they feed on certain naturally occurring marine plankton. The majority of human cases of PSP illnesses occur between spring and fall.  PSP affects the human central nervous system, producing a tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms typically are followed by disturbed balance, lack of muscular coordination, slurred speech and difficulty swallowing. In severe poisonings, complete muscular paralysis and death from asphyxiation can occur.

Domoic acid poisoning (DAP) has been linked in some cases to natural food sources for filter-feeding animals like bivalve shellfish. To date, no known cases of human DAP have occurred in California; but domoic acid has been linked to several episodes of severe poisoning of marine mammals along the Pacific Coast and may have caused several mild cases of human poisoning in the state of Washington. DAP symptoms 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 completely within several days. In severe cases, the victim may experience excessive bronchial secretions, difficulty breathing, confusion, and disorientation, and cardiovascular instability, seizures permanent loss of short‑term memory, coma and death.

There is no known antidote to PSP and DAP and cooking cannot be relied upon to destroy them. Anyone experiencing symptoms of PSP or DAP should seek immediate medical care.

Consumers of sport-harvested, bivalve (two-shelled) clams or scallops are advised to eat only the white meat, removing and discarding the dark-colored organs or viscera before cooking.  Shellfish for human consumption should only be taken from areas free of sewage or chemical contamination during all times of the year.

No commercially harvested shellfish are included in the annual quarantine.  All commercial shellfish harvesters in California are certified by the state and subject to strict requirements to ensure that all oysters, clams and mussels entering the marketplace are free of toxins.  Commercial harvesting is stopped immediately if potentially dangerous levels of toxins are found.

For updated information on quarantines and shellfish toxins, call CDPH’s Shellfish Bio-toxin Information Line at (510) 412-4643 or toll-free at (800) 553-4133.

Last modified on: 6/8/2009 10:25 AM