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Reminding Canadians about the Risks of Eating Raw or Undercooked Shellfish

Starting date:
November 7, 2013
Posting date:
November 7, 2013
Type of communication:
Information Update
Allergen - Fish
Source of recall:
Health Canada
Food Safety
General Public
Identification number:


Are oysters, clams, scallops or mussels a favourite dish of yours? Shellfish is a nutritious food choice, but like all foods it is important to store, handle and prepare shellfish properly, to prevent foodborne illness.

Raw shellfish can carry bacteria, viruses and toxins that can make you seriously ill if proper care is not taken. Children, pregnant women, seniors and people with weakened immune systems are more vulnerable to foodborne illness, so they should avoid eating raw or undercooked shellfish altogether.

There are approximately 4 million cases of foodborne illnesses in Canada every year.  Many of these illnesses could be prevented by following proper food handling and preparation techniques.

What you should do

Buying and storing shellfish

  • Buy shellfish from reputable sources.  A retailer selling raw shellfish should be able to show you a shellfish shipper’s tag. Make sure your shellfish is fresh. Fresh oysters, clams, scallops, mussels and cockles should have tightly closed shells or they should close their shells when you tap them. Refrigerate immediately after you buy and keep them cold (below 4°C).
  • Do not put live shellfish in a closed container or into fresh water. Cover the shells with a damp cloth and place on the lowest shelf of the refrigerator. Store shucked shellfish in a closed container. Raw shellfish can be kept refrigerated for a few days, depending on their freshness and quality, and can be stored in the freezer for 2-4 months. Shucked oysters should be frozen if you do not eat them within two days.
  • If frozen, make sure that the packaging is not torn or open and that there is little frost on the packaging. Too much frost could mean that the shellfish has been frozen for a long time or may have been thawed and refrozen. Put the frozen shellfish in the freezer immediately until you are ready to use it.
  • Defrosting
  • Never defrost shellfish at room temperature! Thaw food in the refrigerator or in cold water. You can use a microwave if you are cooking the shellfish immediately. If thawing in cold water, replace water every 30 minutes. 
  • Keep raw shellfish separate from other foods to prevent cross-contamination. Wash hands before and after handling raw shellfish. Do not use the same plate or utensils for raw and cooked shellfish, and wash counters and utensils with soap and warm water after preparation. 
  • Food should be cooked immediately after thawing.


  • Shucked oysters (oysters without the shell, usually sold in tubs) are not meant to be eaten raw.
  • Cook oysters, clams, scallops, mussels and cockles to minimize the chances of foodborne illness. Follow these guidelines when cooking shellfish:
  • Boil oysters, clams, scallops, mussels and cockles until the shells open, and then boil for an additional 3-5 minutes. You should also boil or simmer shucked shellfish for at least 3 minutes or until the edges curl.
  • Steam for 4-9 minutes and throw out those that did not open.
  • Fry shucked shellfish for at least 3 minutes at 190°C (375°F); and
  • Bake shucked shellfish for at least 10 minutes at 230°C (450°F).


  • If you harvest shellfish yourself, make sure you do so in areas that are open for harvesting. Chemical contaminants or natural toxins from marine algae could be present in shellfish any time of the year, and cooking will NOT destroy these toxins. Contact your nearest Department of Fisheries and Oceans office listed in the blue pages of your local telephone directory for information on areas currently open for shellfish harvesting. You may also want to check with your local or provincial government about harvesting restrictions or consumption advice for shellfish not purchased from commercial establishments.

If you get sick

  • If you’ve eaten shellfish and feel ill, go see a health professional immediately.

Media enquiries

Health Canada
(613) 957-2983

Public enquiries

(613) 957-2991
1-866 225-0709

For more information