Domoic Acid Poisoning

Eating contaminated Shellfish can be life threatening: Always check for Marine Biotoxin and Sanitary Contamination Closures if you plan on harvesting and consuming any shellfish.

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Cooking does not destroy this toxin.

  • Agent: Domoic Acid (ASP)
  • Classification: Marine Biotoxin
  • Fish Species Most Affected:
    • Filter feeding molluscan bivalve shellfish:
    • clams
    • mussels
    • scallops
    • oysters
    • cockles
    • crab hepatopancreas
    • whelks

Most of the toxin within shellfish is normally found within the digestive gland.

Properties of Agents Relevant to Fish Products or Illness

Filter feeding shellfish feed on small fragments of organic matter which they filter from the sea water, including small plants or animals. Some of the small plants (phytoplankton) contain toxins. Pseudo-nitzschia species (including P. australis) are sources of domoic acid on the west coast of Canada. It appears the Pseudo-nitzschia species blooms are periodic; they do not occur every year even though the organisms are apparently frequently present in the seawater.

These toxins are heat stable (cooking and boiling does NOT destroy the toxin).

Characteristic Illness

Amnesic shellfish poisoning is caused by the ingestion of toxin-contaminated bivalve shellfish and crustaceans.

Algal blooms usually occur during the warmer months from June to October, but can also be present any time of the year.


  • nausea
  • vomiting
  • diarrhea
  • short term memory loss
  • temporary or permanent brain damage
  • headaches
  • confusion
  • death

Domoic Acid Poisoning symptoms occur fairly rapidly beginning between 30 minutes to 6 hours after eating contaminated shellfish. If the poisoning is not severe and the individual is not otherwise compromised (e.g., kidney problems), they normally recover completely within a few days. Unfortunately, if the poisoning is severe enough or the individual is not able to excrete domoic acid readily, temporary or permanent brain damage may occur. The syndrome is complex but the most notable simple characteristic is a loss of short term memory, which is why the toxin is sometimes called Amnesic Shellfish Poison (ASP). If you suspect you have a severe case of Domoic Acid Poisoning or should problems persist you should immediately seek medical attention.

At the first sign of such symptoms, contact your Poison Control Center at 1-800-567-8911 for first aid advice and seek medical attention immediately.

Control Measures

The single most effective control measure is responsible harvesting, i.e. to ensure that molluscan bivalve shellfish come only from open harvest areas. Check to ensure that the area where you intend to harvest is open, immediately prior to harvesting,

Call before you harvest
Information is also available on the Fishery Report Record Line at: 1-866-431-3474.

For more information, please visit the Canadian Shellfish Sanitation Program page (Canadian Food Inspection Agency site)