Advisory Remains in Place for Humboldt County and Northern Channel Islands
VENTURA, California –The California Department of Public Health (CDPH) announced that the annual quarantine on mussels gathered by sport harvesters from California’s coastal waters ended on midnight on Friday, October 31, 2025, for the California coast, including Ventura County. Shellfish advisories remain in place for sport-harvested razor clams from Humboldt County and for sport-harvested mussels, clams, scallops, and oysters from the Northern Channel Islands.
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. During the quarantine period, there is a higher risk for concentrated levels of paralytic shellfish poisoning (PSP) toxins and domoic acid to develop in mussels and other bivalve shellfish when they feed on certain naturally occurring marine plankton. PSP and domoic acid toxins remain at low or undetectable levels in mussel samples along all other portions of the California coast. There have been no confirmed reports of shellfish related poisonings in California during this quarantine period.
Advisories remain for Humboldt County and Northern Channel Islands:
– A seafood and shellfish safety notification for Northern Channel Islands sport-harvested mussels, clams, scallops, and oysters remains in place due to domoic acid, which can cause amnesic shellfish poisoning in humans. Additional samples are needed from this area to lift the advisory.
Learn more here: https://www.cdph.ca.gov/Programs/OPA/Pages/SN25-016.aspx
– A seafood and shellfish safety notification for sport-harvested razor clams from Humboldt County also remains in effect. Dangerous levels of naturally occurring domoic acid have been detected in the razor clams. Razor clams are known to retain domoic acid toxin in their meat and tissues much longer than other species of bivalve shellfish.
Learn more here: https://www.cdph.ca.gov/Programs/OPA/Pages/SN24-003.aspx
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.
To receive the most current information on shellfish advisories and quarantines, call CDPH’s toll-free Shellfish Information Line at (800) 553-4133 or view the recreational bivalve shellfish advisory interactive map.
Recreational Bivalve Shellfish Advisory Interactive Map: https://experience.arcgis.com/experience/394836318cfe4f7494e1c09097a43559/
For additional information, please visit the CDPH Marine Biotoxin Monitoring web page or the Annual Mussel Quarantine – Frequently Asked Questions (FAQs) web page.