How to Buy, Handle and Prepare Seafood

Seafood is a healthy choice, but it must be handled properly to prevent food-borne infections and other health risks.
How to Buy, Handle and Prepare Seafood
September 24, 2019

Seafood, such as fish and shellfish, are nutritious foods that can be enjoyed in a variety of ways; however, food businesses and Food Handlers should be aware of the potential health hazards associated with them.

Seafood can carry bacteria, parasites, viruses and toxins that can cause food-borne illnesses. Many species of fish contain parasites, and high concentrations of bacteria, toxins and other harmful microorganisms can accumulate in the bodies of shellfish, particularly filter-feeders like oysters, clams, scallops, mussels and cockles.

As with all high-risk foods, it’s important to buy, store, handle and prepare seafood properly to prevent food-borne illness and other serious health risks.

Buying seafood


Always purchase fish from a reputable supplier and check that it is fresh, shows no signs of spoilage and is displayed or delivered at a safe temperature (4°C / 40°F or below).

When buying or accepting a fish delivery, check to ensure that:

  • it smells fresh and mild
  • its eyes are clear and shiny
  • the flesh is firm and springs back when pressed
  • there are no strong odours 
  • it isn't discoloured, dark or dry around the edges

Note: Fresh fish and fish fillets sold as “previously frozen” may not have all the characteristics of fresh fish, but they should still smell fresh and mild. Reject any previously frozen fish that smells fishy, sour or rancid.


When buying or accepting a shellfish delivery, make sure that it is fresh; shellfish spoil rapidly after death, which increases the risk of food poisoning and other infections from disease-causing microorganisms or toxins.

To make sure you’re buying only fresh (ahem, safe) shellfish, do the following:

  1. Check that bivalve molluscs (e.g. oysters, clams, scallops, mussels) have tightly closed shells.
  2. Do a tap test — if bivalves don’t close when you tap them, they are probably dead (don’t buy those).
  3. Discard any cracked or broken bivalves.
  4. Check for leg movement — live crabs and lobsters in the tank should show at least some leg movement.
  5. Choose lively lobsters — live lobsters should move their claws, legs and even curl their tails when they’re lifted out of the tank.
  6. Do a smell test — fresh shellfish should be odourless or have a mild “ocean” scent, but they should not smell fishy, sour, rancid or ammonia-like.

Remember, you should only buy shellfish from a reputable supplier. A retailer selling raw shellfish should be able to show you a shellfish shipper’s tag.

Storing seafood

Store seafood:

  • in the refrigerator at 4°C / 40°F or below
  • in the freezer at -18°C / 0°F or below

If your business keeps live seafood in tanks, make sure the tanks are well-maintained and aerated. Fill them with clean water and remove any dead fish or shellfish from the tanks immediately. Make sure the water in the tank is appropriate for the type of fish or shellfish you’re keeping in it, and never mix saltwater and freshwater seafood in the same tank!

Fish and shellfish are common food allergens, so keep them in the original containers in which they were delivered, well away from other types of food to prevent cross-contamination (more on preventing cross-contamination below).

Use fresh seafood within two days — and don’t just freeze and forget about seafood! Freezer-burned seafood might not be a safety hazard, but the texture and taste can deteriorate, which is unlikely to impress your customers.

Preparing seafood


Never defrost seafood at room temperature. The best and safest way to defrost seafood is in the refrigerator overnight, but if you’re in a hurry, you can also thaw it under cool running water or in the microwave.

To thaw in the refrigerator:

  1. Place the seafood in a clean container or leak-proof platter.
  2. Place the container or platter on the bottom shelf of the refrigerator.
  3. Cook it immediately after it is thawed.

To thaw under cool running water:

  1. Thoroughly clean and sanitize the sink before thawing the seafood.
  2. Make sure it's wrapped in leak-proof plastic to prevent cross-contamination.
  3. Run cool, potable drinking water on it until it has thawed.

To thaw in the microwave:

  1. Use the defrost setting on the microwave and stop the cycle when the seafood is still icy but pliable.
  2. Only use this method if you will be cooking the seafood immediately.


Fish should be cooked to a minimum internal temperature of 70°C / 158°F; shellfish should be cooked to 74°C / 165°F.

If cooked through, you should observe the following (but always use a food thermometer to be sure!):

  • Fish: flesh flakes easily
  • Shrimp, scallops, crab and lobster: flesh becomes firm and opaque
  • Clams, mussels and oysters: shells open during cooking (throw out any that don’t open)

Note: Sour, rancid or fishy odours in spoiled seafood become stronger after cooking. If you smell sour, rancid or fishy odours — or an odour that smells like ammonia — in a cooked seafood dish, don’t serve it. 

Preventing cross-contamination

Cross-contamination occurs when contaminants like bacteria or food allergens are accidentally transferred from a person, surface or substance into food, making it unsafe to eat.

Everyone who handles food in your business must be trained on how to prevent cross-contamination, as well as how to manage food allergies. Visit the CIFS Food Handler course page to find out more about our online food safety training.

Fish and shellfish are common allergens in Canada, so handle with extreme care and be sure to do the following:

  • Keep raw and cooked seafood separate.
  • Store raw seafood on the bottom shelf of your fridge, below cooked or ready-to-eat food.
  • Use separate cutting boards, cooking equipment and utensils to prepare allergen-free meals.
  • Use separate cutting boards and utensils to prepare raw and cooked seafood.
  • Clean and sanitize all surfaces, equipment and utensils before and after preparation.
  • Wash your hands thoroughly and frequently before and after handling seafood.

If you use fish or shellfish to flavour soups, stocks, broths or sauces, or if you include small amounts of seafood in other dishes, remember to let your customers know so that those with seafood allergies can make informed choices.

What you should know about raw seafood

Some types of seafood are commonly eaten raw. Serving raw seafood is inherently risky, because many species of fish, crustaceans and molluscs contain dangerous parasites and other pathogenic microorganisms, such as:

  • Listeria
  • Salmonella
  • Staphylococcus aureus
  • Vibrio parahaemolyticus

Freezing seafood can kill parasites, but won’t kill all harmful bacteria, so cooking is always the safest way to serve seafood. Vulnerable customers — including pregnant women, children, the elderly and people with impaired immune systems — are particularly at risk of food-borne illness and should avoid raw seafood.