January 2024 Marine Biotoxin Monitoring Monthly Report

The following is a list of recent Quarantines and Health Advisories for bivalve shellfish prior to February 1, 2024. For access to current advisories, please refer to the end of this report.

● The annual mussel quarantine on sport-harvested mussels ended at midnight, October 31 for all counties except San Mateo and San Luis Obispo, which were removed from the quarantine notice on November 20 and December 12, respectively. This quarantine normally begins each year on May 1 and extends through at least October 31. The quarantine applies to all species of mussels that are recreationally harvested for human consumption along the California coast, including all bays and estuaries. During the quarantine, mussels may only be harvested for use as bait. The quarantine is in place to protect the public against poisoning that can lead to serious illness, including coma and death. 

● On December 12 CDPH lifted the PSP shellfish advisory related to sport-harvested mussels, scallops, and clams in San Luis Obispo County.

● On November 20 CDPH lifted the PSP shellfish advisory related to sport-harvested mussels, scallops, and clams in San Mateo County.

● On November 9 CDPH issued a health advisory warning consumers not to eat sport-harvested razor clams from Del Norte County due to dangerous levels of domoic acid (see October monthly report for data).

● On October 27 CDPH announced that the annual mussel quarantine would end at midnight, October 31 for all counties except San Mateo and San Luis Obispo. CDPH also lifted the PSP shellfish advisory related to sport-harvested mussels, scallops, and clams in Mendocino County

● On September 7 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from Mendocino County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.

● On August 3 CDPH lifted the domoic acid shellfish advisory related to related to sport-harvested razor clams in Humboldt County.

● On August 1 CDPH lifted the domoic acid shellfish advisory related to related to sport-harvested mussels, scallops, and clams in Santa Barbara County.

● On July 28 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from San Mateo County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.

● On July 14 CDPH issued a health advisory warning consumers not to eat sport-harvested mussels, clams, or scallops from San Luis Obispo County due to dangerous levels of the paralytic shellfish poisoning toxins in shellfish samples.

● On July 6 CDPH lifted the shellfish advisory related to sport-harvested razor clams in Del Norte County. The  safety notification was issued on November 3, 2022  due to dangerous levels of naturally occurring domoic acid, also referred to as Amnesic Shellfish Poisoning. Razor clams have been continually tested and have now met the criteria for lifting the safety notification in Del Norte County. An advisory for razor clams in Humboldt County remains in effect.

On June 16 CDPH advised consumers not to eat sport-harvested mussels, clams, or scallops from Santa Barbara County due to the presence of dangerous levels of domoic acid in shellfish samples.

● On May 1 CDPH initiated the annual quarantine of sport-harvested mussels gathered along the California coast. The quarantine normally extends from May 1 through October 31, although elevated toxin levels can extend the quarantine period. This annual quarantine applies to all species of mussels that are recreationally harvested for human consumption along the California coast, including all bays and estuaries. The quarantine is in place to protect the public from poisoning that can lead to serious illness, including coma and death.

 Consumers of Washington clams, also known as butter clams (Saxidomus nuttalli), are cautioned to eat only the white meat. Washington clams can concentrate the PSP toxins in the viscera and in the dark parts of the siphon and can remain toxic for a long period of time. Persons taking scallops or clams, with the exception of razor clams, are advised to remove and discard the dark parts (i.e., the digestive organs or viscera). Razor clams (Siliqua patula) are an exception to this general guidance due to their ability to concentrate and retain domoic acid in the edible white meat as well as in the viscera.

PSP toxins can produce a tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms can be 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.

Symptoms of domoic acid poisoning can occur within 30 minutes to 24 hours after eating toxic seafood. In mild cases, symptoms of exposure to this nerve toxin 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, disorientation, cardiovascular instability, seizures, permanent loss of short-term memory, coma and death.

Any person experiencing any of these symptoms should seek immediate medical care. Consumers are also advised that neither cooking or freezing eliminates domoic acid or the PSP toxins from the shellfish tissue. These toxins may also accumulate in seafood species such as crab, lobster, and small finfish like sardines and anchovies.

Sportharvesters should only collect shellfish from areas that are not affected by a current health advisory or quarantine.

Contact the “Biotoxin Information Line” at 1-800-553-4133 or view the  recreational bivalve shellfish advisory interactive map  for a current update on marine biotoxin activity prior to gathering and consuming shellfish.