October 2022 Marine Biotoxin Monitoring Monthly Report

This report contains results from the California Department of Public Health (CDPH) monitoring programs for shellfish toxins and associated toxin-producing phytoplankton. Toxin concentration ranges are provided for the paralytic shellfish poisoning (PSP) toxins and for domoic acid, the latter associated with the syndrome called Amnesic Shellfish Poisoning. Estimates are provided for the distribution and relative abundance of Alexandrium, the dinoflagellate that produces PSP toxins, and Pseudo-nitzschia, the diatom that produces domoic acid. This report also contains summary information for any quarantine or health advisory in effect during the reporting period. Finally, lists of participating agencies and volunteers for each monitoring effort are provided.

Please note the following conventions for the phytoplankton and shellfish biotoxin distribution maps:

The Marine Biotoxin Monitoring and Control Program, managed by the California Department of Public Health, is a state-wide effort involving a consortium of participating organizations, agencies, and volunteer samplers.

The phytoplankton sampling and observation element of the biotoxin monitoring program is a state-wide effort designed to detect toxin producing species of phytoplankton in ocean waters before they impact shellfish resources. The phytoplankton monitoring and observation effort can provide an advanced warning of a potential toxic bloom, allowing us to focus sampling efforts in the affected area before California's valuable shellfish resources or the public’s health is threatened.

Historically, the majority of shellfish toxicity episodes in California have originated along the open coast, occasionally moving into bays and estuaries. The shellfish sampling element of the program provides an early warning of shellfish toxicity by routinely assessing coastal resources for the presence of paralytic shellfish poisoning (PSP) toxins and domoic acid. Routine shellfish sampling is essential for protecting the public from these dangerous toxins.

For Information on Volunteering: Email  redtide@cdph.ca.gov  or call 510-412-4635

The following is a list of recent Health Advisories and Quarantines for bivalve shellfish prior to November 1, 2022. For access to current advisories, please refer to the end of this report.

● On October 31 CDPH rescinded the statewide annual quarantine on mussels taken by sport harvesters from California's ocean waters as of midnight on Monday, October 31, 2022, for all coastal counties except Humboldt, San Mateo, Monterey, and San Luis Obispo. The warning against eating sport-harvested bivalve shellfish (including mussels, clams, and scallops) from  Humboldt ,  San Mateo , Monterey, and  San Luis Obispo  counties remain in effect, due to elevated levels of PSP toxins detected in mussels from these counties. 

● On October 27 CDPH advised consumers not to eat sport-harvested mussels, clams, or whole scallops from Humboldt and San Luis Obispo counties, due to dangerous levels of PSP toxins detected in a mussel sample collected in August.  

● On September 2 CDPH advised consumers not to eat sport-harvested mussels, clams, or whole scallops from San Mateo County, due to dangerous levels of PSP toxins detected in a mussel sample collected in August.  

● On June 27 CDPH rescinded the December 16, 2021 health advisory for razor clams in Del Norte County. Recent testing demonstrated that concentrations of domoic acid had returned to safe or undetectable levels in razor clams.

● On April 26 CDPH announced the May 1 start of the annual quarantine of sport-harvested mussels gathered along the California coast. 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.

 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.