Susan Buckley, RN, Director, Public Health
Ira Singh, MPH, Deputy Director
Donald I. Baird, MD, Health Officer

Division of Environmental Health


Date Released: 11/8/2012
Subject: Local mussel quarantine expanded to include other shellfish
Contact: Heather Shelton
Phone: 441-5547

The Department of Health and Human Services’ Division of Environmental Health is adding sport-harvested clams and whole scallops to the list of Humboldt County bivalve shellfish that consumers should avoid. This is in addition to the Nov. 6 advisory issued by the California Department of Public Health (CDPH) for all sport-harvested bivalve shellfish in Del Norte County and the annual mussel quarantine that was extended Oct. 31 for both Del Norte and Humboldt counties.

Dangerous levels of paralytic shellfish poisoning (PSP) toxins have been detected in mussels from the North Coast; clams and scallops may also pose a health risk. The naturally occurring PSP toxins can cause illness or death in humans.
This warning does not apply to commercially sold clams, mussels, scallops or oysters from approved sources. State law permits only certified commercial shellfish harvesters or dealers to sell these products, because shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing.

PSP toxins affect the 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 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. Cooking does not destroy the toxin.
According to the CDPH, there is no way to visibly determine if mussels or any other seafood contain dangerous levels of these toxins. The toxins do not affect the appearance or behavior of the shellfish in any way. The only way to tell if the shellfish are toxic is through testing by an approved laboratory.

For updated information about shellfish poisoning and quarantines, call CDPH’s toll-free “Shellfish Information Line” at 800-553-4133.

For more information, visit the CDPH Marine Biotoxins Frequently Asked Questions Web page at


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