Shellfish is a culinary term for aquatic animals that are not fish, mammals, or reptiles, that are used as food; generally, mollusks, crustaceans, and echinoderms. Both salt-water and freshwater invertebrates are considered shellfish. Mollusks commonly used as food include the clam, mussel, oyster, winkle, and scallop. Some crustaceans commonly eaten are the shrimp and prawn, lobster, crayfish, and crab. Echinoderms are not eaten as commonly as molluscs and crustaceans. In Asia, sea cucumber and sea urchins are eaten. Edible cephalopods such as squid, octopus, and cuttlefish and terrestrial snails, though all molluscs, are sometimes considered to be shellfish and sometimes not.
The term finfish is sometimes used to distinguish ordinary (vertebrate) fish from shellfish.
Usage in various cuisines
Shellfish dishes are a feature of all the cuisines of the world, with a few exceptions.
Lobster in particular is a great delicacy in the United States, where families in the north-east region make them into the centerpiece of a clam bake, usually for a special occasion. Lobsters are eaten on much of the East Coast; the American lobster ranges from Newfoundland down to about the Carolinas, but is most often associated with Maine. A typical meal involves boiling the lobster with some slight seasoning and then serving with drawn butter, baked potato, and corn on the cob.
Clamming is done both commercially and recreationally along the North-east coastline of America. Various type of clams are incorporated into the cuisine of New England. Notable is the soft-shelled clam, which is eaten fried or steamed, where they are called 'steamers.' Many types of clams can be used for clam chowder, but quahogs, a hard shelled clam also known as a chowder clam, are often used because the long cooking time softens its tougher meat.
The Chesapeake Bay and Maryland region has generally been associated more with crabs, but in recent years the area has been trying to reduce its catch of blue crabs as wild populations have been depleted. This has not, however, stemmed the demand: Maryland style crabcakes are still a well known treat in crabhouses all over the bay, though the catch now comes from points farther south.
In the South-east, and particularly the gulf states, shrimping is an important industry. Copious amounts of shrimp are harvested each year in the Gulf of Mexico and the Atlantic Ocean to satisfy a national demand for shrimp. Locally, prawns and shrimp are often deep fried; in the Cajun and Creole kitchens of Louisiana, shrimp and prawns are a common addition to traditional recipes like jambalaya and certain stews. Crayfish are a well known and much eaten delicacy here, often boiled in huge pots and heavily spiced.
In many major cities with active fishing ports, raw oyster bars are also a feature of shellfish consumption. When served freshly shucked (opened) and iced, one may find a liquid inside the shell, called the liqueur. This is a primary feature of the raw bar, and should be sampled, if not enjoyed. Some believe that oysters have the properties of an aphrodisiac. "Rocky Mountain oysters" is a euphemism for bull testicles, as their appearance and preparation is similar.
Jewish Kosher Law traditions forbid the eating of shellfish, as do some interpretations of Islamic dietary laws. A rational basis taken up by some non-religious people is the tendency of some shellfish to feed on waste or accumulate heavy metals or toxins in their tissues. Another is that some of these dishes are consumed raw (oysters, mussels, clams and shrimp, most notably) and have the potential to cause serious illness from shellfish poisoning. Some people suffer from potentially-fatal allergies to shellfish.
Shellfish are an important part of a healthful diet. They contain high quality protein and other essential nutrients, can be low in saturated fat, and may contain omega-3 fatty acids. In fact, a well-balanced diet that includes a variety of fish and shellfish can contribute to heart health and children's growth and development. But, as with any type of food, it's important to handle seafood safely in order to reduce the risk of food borne illness. Follow these basic food safety tips for buying, preparing, and storing fish and shellfish - and you and your family can safely enjoy the fine taste and good nutrition of seafood.
Why Freshness Counts
Healthwise, it is important to look for freshness when choosing seafood. In some species, if the catch has been left out in the sun too long - or the fish haven't been transported under proper refrigeration - toxins known as scombrotoxin, or histamine, can develop. Eating spoiled shellfish that have high levels of these toxins can cause illness.
Today, fresh catches can be processed and frozen immediately to very low temperatures - frequently, this takes place right on the fishing vessel. However, frozen seafood can spoil if it thaws during transport and is left at warm temperatures for too long.
To help ensure that the frozen shellfish you're buying is safe, follow these guidelines:
- Don't buy frozen seafood if its package is open, torn or crushed on the edges.
- Avoid packages that are positioned above the "frost line" or top of the freezer case in the store's freezer.
- If the package cover is transparent, look for signs of frost or ice crystals. These could mean the fish has been stored a long time or thawed and refrozen - in which case, choose another package.
Selecting Shellfish: Some Special Guidelines
In the United States, the Food and Drug Administration requires shellfish harvesters and processors of oysters, clams, and mussels to put a tag on sacks or containers of live shellfish (in the shell), and a label on containers or packages of shucked shellfish.
- Tags and labels contain specific information about the product, including a certification number for the processor, which means that the shellfish were harvested and processed in accordance with national shellfish safety controls.
- Ask to see the tag or check the label when purchasing shellfish.
In addition, follow these general guidelines:
- Discard Cracked/Broken Ones: Throw away clams, oysters, and mussels if their shells are cracked or broken.
- Do a "Tap Test": Live clams, oysters, and mussels will close up when the shell is tapped. If they don't close when tapped, do not select them.
- Check for Leg Movement: Live crabs and lobsters should show some leg movement. They spoil rapidly after death, so only live crabs and lobsters should be selected and prepared.
Put seafood on ice or in the refrigerator or freezer soon after buying it, using these guidelines for safe storage
- If seafood will be used within two days after purchase, store it in the refrigerator.
- If seafood won't be used within two days after purchase, wrap it tightly in moisture-proof freezer paper or foil to protect it from air leaks, and store it in the freezer.
Thaw frozen seafood gradually by placing it in the refrigerator overnight. If you have to thaw seafood quickly, either seal it in a plastic bag and immerse it in cold water, or - if the food will be cooked immediately thereafter - microwave it on the "defrost" setting and stop the defrost cycle while the fish is still icy but pliable.
When you're preparing fresh or thawed seafood, it's important to prevent bacteria from the raw seafood from spreading to ready-to-eat food. Take these steps to avoid cross-contamination between raw and cooked foods:
- Wash hands thoroughly with soap and warm water before and after handling any raw food.
- Wash the cutting board with soap and hot water to remove food particles and juices after using it for raw foods such as seafood, and before using the board for cooked or ready-to-eat foods or preparing another food item.
- As an added precaution, sanitize cutting boards by rinsing them in a solution made of one teaspoon of chlorine bleach in one quart of water - or run the plastic board through the wash cycle in your automatic dishwasher. Or, consider using one cutting board only for raw foods and another only for ready-to-eat foods such as bread, fresh fruit and vegetables, and cooked fish.
- As a rule of thumb, avoid using cutting boards that are made of soft, porous materials. Instead, choose those made of hard maple or plastic, and make sure they are free of cracks and crevices. Smooth surfaces can be cleaned more easily and thoroughly.
Most seafood should be cooked to an internal temperature of 145 °F. But if you don't have a food thermometer, there are other ways to determine whether seafood is done.
- Shrimp and Lobster: The flesh becomes pearly-opaque.
- Scallops: The flesh turns milky white or opaque and firm.
- Clams, Mussels, and Oysters: Watch for the point at which their shells open, which means they're done. Throw out the ones that don't open.
List of shellfish
- Haskin Shellfish Research Laboratory at Rutgers University
- Shellfish Gallery from the Shellfish Association of Great Britain
- Shellfish Facts
- University of Washington Libraries Digital Collections -- Freshwater and Marine Image Bank -- Shellfish An ongoing digital collection of images related to shellfish.
- This module uses content from the Wikipedia article "w:Shellfish", under the terms of the GNU Free Documentation License.
- This module uses content from the public domain article "Fresh and Frozen Seafood: Selecting and Serving it Safely" from the United States Food and Drug Administration.