Diarrhetic Shellfish 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.

Go to the latest Biotoxin Contamination update


Cooking does not destroy this toxin.

  • Agent: Diarrhetic Shellfish Poisoning (DSP)  
  • Classification: Marine Biotoxin
  • Fish Species Most Affected:
  • Filter feeding molluscan bivalve shellfish:
    • Mussels
    • Clams
    • Cockles
    • Oysters
    • Scallops
    • Crab hepatopancreas
    • Whelks

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

Properties of the Agent Relative to the Food and 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. The primary sources of diarretic shellfish poisoning on the west coast of Canada are from toxic species of dinoflagellates including Dinophysis and Prorocentrum.  The main types of toxins associated with diarrhetic shellfish poisoning are okadaic acid, dinophysis toxins and pectenotoxins. 

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

Characteristics of the Illness

Diarrhetic shellfish poisoning is caused from the ingestion of toxin-contaminated bivalve shellfish and crustaceans.  Mussels are the most common species affected and associated with diarrhetic shellfish illnesses.   

Algal blooms of dinoflagellates, usually occur during the warmer months from June to October however they can also be present anytime of the year.   


  • diarrhea (watery)
  • nausea
  • abdominal cramps
  • chills
  • vomiting
  • headache

DSP symptoms occur fairly rapidly beginning between 30 minutes to 15 hours after eating contaminated shellfish.  The symptoms usually start in one or two hours.  The recovery period is within 3 days. There are no known complications from diarrhetic shellfish poisoning.  If you suspect you have a severe case of DSP or should problems persist you should immediately seek medical attention.

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

Control Measures – How to protect yourself from contamination

The single most effective control measure is responsible harvesting, i.e. 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)

Related Links


For more information about Shellfish Closures, please contact :

Phone: 250-756-7192

Resource Management
Canadian Shellfish Sanitation Program (CSSP) Coordinator
DFO South Coast Division
3225 Stephenson Point Rd.
Nanaimo, BC V9T 1K3

Phone: 250-339-3799
Fax: 250-339-4612

Resource Management
DFO South Coast Division
148 Port Augusta St.
Comox, BC V9M 3N6

Shellfish Toxin Updates

Toll free: 1-866-431-FISH

Recorded information

or visit your local DFO Office.