​October 30, 2024 
SN24-015

Shellfish Safety Notification continues for Del Norte, Marin, and Monterey counties

What You Need to Know: The statewide annual quarantine on mussels taken for human consumption by sport-harvesters from California's ocean waters ends at midnight on Thursday, October 31, 2024, for all coastal counties except Del Norte, Marin, and Monterey. 

Sacramento – The California Department of Public Health (CDPH) announced today that the statewide annual quarantine on mussels taken for human consumption by sport-harvesters from California's ocean waters ends at midnight on Thursday, October 31, 2024, for all coastal counties except Del Norte, Marin, and Monterey.  

CDPH warns against eating sport-harvested bivalve shellfish (including mussels, clams, and scallops) from Del Norte, Marin, and Monterey counties, due to elevated levels of paralytic shellfish poisoning (PSP) toxins detected in mussels from these counties and/or absence of recent data to lift the advisories. The naturally occurring PSP toxins can cause illness or death in humans. Unfortunately, cooking does not destroy the toxins.   

Domoic acid and PSP toxins remain at low or undetectable levels along all other portions of the California coast. Concentrated levels of PSP toxins and domoic acid can develop in mussels and other bivalve shellfish when they feed on certain naturally occurring marine plankton that can increase during favorable environmental conditions.  

The annual quarantine on sport-harvested mussels for human consumption, which typically runs May 1 through October 31, is intended to protect the public from shellfish poisoning caused by marine biotoxins. There have been no reports of shellfish related poisonings in California during this quarantine period.  

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.  

Domoic acid toxin can cause amnesic shellfish poisoning. 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. Severe cases may experience trouble breathing, confusion, disorientation, cardiovascular instability, seizures, excessive bronchial secretions, permanent loss of short-term memory, coma or death.  

CDPH's shellfish sampling and testing programs issue warnings or quarantines when needed. Local health departments, various state, federal and tribal agencies, community groups and others participate in the monitoring program. Residents and community groups interested in volunteering to assist with the testing program should email redtide@cdph.ca.gov or call (800) 553-4133. 

​You can get the most current information on shellfish advisories and quarantines by calling CDPH's toll-free Shellfish Information Line at (800) 553-4133 or viewing the recreational bivalve shellfish advisory interactive map. For additional information, please visit the CDPH Marine Biotoxin Monitoring web page.