CDPH Lifts Domoic Acid Warning for Del Norte County Razor Clams​

July 29, 2025​

SN25-017​

Warning for all bivalve shellfish remains in effect for Del Norte County due to paralytic shellfish poisoning toxins

​What You Need to Know: CDPH has removed warnings for sport-harvested razor clams in Del Norte County as recent testing shows concentrations of domoic acid are now at safe or undetectable levels. Advisories for razor clams in Humboldt County, and for sport-harvested mussels, clams, scallops and oysters in Del Norte County, remain in effect.

SACRAMENTO – The California Department of Public Health (CDPH) has lifted the shellfish safety notification related to domoic acid in sport-harvested razor clams in Del Norte County. The safety notification was issued on November 9, 2023 due to dangerous levels of naturally occurring domoic acid.  

Domoic acid is a marine biotoxin that can cause as Amnesic Shellfish Poisoning (ASP). ASP can result in severe illness or death in humans. Recent testing shows concentrations of domoic acid are now at safe or undetectable levels in razor clams in Del Norte County. An advisory for razor clams in Humboldt County remains in effect.  

Razor clams are known to retain domoic acid toxin in their meat and tissues much longer than other species of bivalve shellfish. Domoic acid was present in the razor clams due to the occurrence of toxin-producing marine phytoplankton. Razor clams have been continually tested and have now met the criteria for lifting the domoic acid safety notification in Del Norte County.  

Symptoms of domoic acid poisoning, also referred to as 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. In severe cases, the victim may experience trouble breathing, confusion, disorientation, cardiovascular instability, seizures, excessive bronchial secretions, permanent loss of short-term memory, coma, or death.  

The July 3 warning advising consumers not to eat sport-harvested mussels, clams, scallops, or oysters from Del Norte County remains in effect. Dangerous levels of paralytic shellfish poisoning (PSP) toxins have been detected in mussels from Del Norte County. The naturally occurring PSP toxins can cause illness or death in humans. Cooking does not destroy the toxin. 

This warning does not apply to commercially sold mussels, clams, scallops, or oysters from approved sources. State law permits only state-certified commercial shellfish harvesters or dealers to sell these products. Shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing to monitor for toxins. 

Paralytic shellfish poisoning 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. 

For 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. For additional information, please visit the CDPH Marine Biotoxin Monitoring web page.  ​​​