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How to Buy and Cook Shellfish

Created January 10, 2017
Shrimp and rice

Shellfish, including shrimp, lobster, scallops, clams and crab, add a taste of the sea to many wonderful recipes. Check out the selection at your local grocery store or fish market for both fresh and frozen varieties. 

Shellfish can be grouped into two main categories: 

  • Crustaceans—long bodies with soft, jointed shells and legs. Include crabs, crayfish, lobster and shrimp. 
  • Mollusks—soft bodies with no spinal column and covered by a shell in one or more pieces. Include clams, mussels, oysters, scallops, octopus, squid, abalone and snails. 

Imitation Seafood Products 

Imitation seafood products like crab legs or pieces, lobster pieces and scallop pieces are less expensive than shellfish but provide a similar taste and texture in recipes. It is usually made from pollock, a mild white-fleshed fish. 

How to Buy Shellfish 

  • Clams, mussels and oysters in shells should be purchased alive. Look for tightly closed shells that are not cracked, chipped or broken. They should have a mild odor. The shells may open naturally but will close if lightly tapped, indicating it is still alive. Throw out any that are dead. 
  • Shucked clams, mussels and oysters (no shells) should be plump and surrounded by a clear, slightly milky or light gray liquid. 
  • Scallops should look moist, have a mild, sweet odor and not be standing in liquid or in direct contact with ice. They are usually creamy white and may be tinted light orange, light tan or pink. 
  • Live crabs and lobsters will show some leg movement, and lobsters will curl their tails under when picked up. They both must be cooked live or killed immediately before cooking; throw out any that are dead. Crabmeat is available in a pasteurized fresh form, and both crab and lobster meat are available frozen and canned. 
  • Shrimp are sold either raw (“green”) with the heads on; raw in the shell without the heads; raw and peeled and deveined (“cleaned”); cooked in the shell; or cooked, peeled and deveined. They should have a clean sea odor; if they smell like ammonia, don’t purchase them. Fresh shrimp are sold by a descriptive size name like “jumbo” or “large,” and by “count,” or number per pound. The larger the shrimp, the lower the count. 
  • Squid, also known as calamari, should be cream colored with reddish brown spots. As squid ages, the skin will turn pinkish. Buy fresh squid that’s whole with clear eyes and a clean sea odor. It’s also available cleaned. Cleaned squid should be in juices, and the meat should be firm. 
  • Soft-shell crabs are actually the same species as Atlantic hard-shell blue version, except the soft-shell crabs have been caught immediately after shedding their old hard shells. They stay soft for only a couple of hours. When their new shells harden, they are known as hard-shell blue crabs. Like all live crabs, they should be cooked the same day they’re purchased. 

How to Store Shellfish 

  • Live crabs (hard or soft shell) and lobster should be cooked the same day purchased. Before cooking, put them on a tray with sides, cover with a damp cloth and refrigerate. 
  • Scallops, shrimp, squid and shucked shellfish should be stored in a leakproof bag or plastic container with a lid. Use scallops, shrimp and squid within 1 to 2 days. Shucked shellfish should be used within 7 days. 
  • Live clams, mussels and oysters should be refrigerated in containers covered with clean, damp cloths—not with airtight lids or in plastic bags, which will cause suffocation. They may open their shells even when refrigerated. Give the shells a tap—they will close if alive; if not, throw them out. Use within 1 to 2 days. 

HELPFUL HINT: For more information about shellfish handling, safety and nutrition, contact the Food and Drug Administration’s Center for Food Safety and Applied Nutrition at 1-888-SAFEFOOD (723-3366) or

How to Cook Shellfish 

Cooked shellfish should be moist and slightly chewy; overcooking makes it tough and rubbery. Follow these guidelines to determine when it is done: 
  • Crabs and lobsters will turn bright red. 
  • Scallops turn milky white or opaque and become firm. Cooking time depends on the size. 
  • Raw shrimp will turn pink and become firm. Cooking time depends on the size. 
  • Live clams, oysters and mussels will open their shells as they are done. 
  •  Shucked clams, oysters and mussels will become plump and opaque. Oyster edges will start to curl.