Introduction to Fish and Shellfish

Fish, as both a source of food and as a commercial industry, is an important resource worldwide. In many diets around the world, especially in Asia and the Mediterranean region, seafood is an important source of protein. With the improved transportation and preservation techniques used today, quality fish and shellfish are more readily available in retail markets and foodservice operations.

Seafood refers to any animal or plant that lives in a body of water that is consumed. Seafood includes seawater animals, such as fish and shellfish, and edible seaweeds. Seafood is often distinguished from meat, although it is still an animal, and is excluded in a vegetarian diet.

Fish refers to aquatic vertebrates that have fins for swimming and gills for breathing. This includes salt- and freshwater varieties. There are two subgroups: round fish and flatfish.

  • Round fish swim in a vertical position and have eyes on both sides of their heads. Their body shape can be round, oval or compressed. Examples include bass, catfish, cod, and grouper.
  • Flatfish have asymmetrical compressed bodies, swim in a horizontal position and have both eyes on top of their heads. They usually dwell on the bottom of deep ocean waters. Examples include flounder and halibut.

Shellfish are aquatic invertebrates with shells or exoskeletons. There are two subgroups: crustaceans and mollusks.

  • Mollusks are characterized by soft bodies with no internal skeleton, yet most mollusks have hard outer shells. Examples include clams, oysters, and mussels. Squid and octopus are also mollusks, although they are known as cephalopods, since they do not have a hard outer shell.
  • Crustaceans have a hard outer skeleton or shell with jointed appendages. Examples include lobsters, crab and shrimp.

Fishing is the harvesting of wild seafood.

Aquaculture or aquafarming is the farming of seafood. It involves cultivating freshwater and saltwater animals under controlled conditions. Half of the world’s seafood supply originates from aquaculture.

Sustainable seafood is seafood from either fished or farmed sources that can maintain or increase production in the future without jeopardizing the ecosystems from which it was acquired. The sustainable seafood movement has gained momentum as more people become aware about both overfishing and environmentally-destructive fishing methods. Two most recognized certifications for product sustainability are provided by the Marine Stewardship Council and the Aquaculture Certification Council.

Marine Stewardship Council (MSC) is a global, independent, non-profit organization that was established to find a solution to today’s over fishing of marine wildlife. MSC provides environmental standards based on the condition of the fish stocks, the impact of the fishery on the marine environment, and the fishery management systems.

Aquaculture Certification Council is a nonprofit, nongovernmental organization created to certify social, environmental and food safety standards at aquaculture facilities throughout the world.

Fish and Shellfish Varieties

With more than thirty thousand species of seafood in existence, this overview includes only the most common varieties in the retail market.

Round Fish

Catfish is a fresh water species with mild, slightly sweet flesh and a moderate fat content. Popular among Southern states, it is a favorite to deep-fry or pan-fry.

Sea bass is comprised of many varieties, each with their own nuances of flavor and texture. Most have a rich, sweet flavor and a firm texture.

Cod, with its mild, flaky flesh, is typically battered and fried for fish and chips. It can be prepared using any cooking method, except for grilling.

Haddock is a member of the cod family and shares the same delicate texture, but has more flavor.

Grouper has lean, firm meat with a slightly sweet flavor. It is versatile to prepare using any cooking method.

Mahi-mahi is known by many names, including dorado and dolphinfish. It has firm, lean flesh and a pronounced sweetness. This fish can be broiled, grilled or baked.

Orange roughy has a low fat content and a very mild flavor. Its firm texture makes it a good choice for the grill or the broiler.

Red snapper is commonly served whole at restaurants. It is characterized by its flaky flesh and sweet flavor and can be prepared using any cooking method.

Salmon is one of the most popular fish consumed. Wild salmon have a distinct orange-pink hue. Farm raised salmon, on the other hand, have added color because they have a lighter hue. The point of origin, such as Norwegian, Scottish, is usually indicated on menu mentions and retail packaged salmon. Chinook or King Salmon are from the Pacific region. Salmon can be prepared using any cooking method.

Swordfish, is a very large fish and feeds on smaller fish, so it has a higher mercury content than most other fish. Its firm flesh is very lean and meaty, which makes it perfect to grill.

Tilapia is another very popular fish. Its sweet, firm and lean meat is extremely adaptable to any cooking method.

Trout has a moderate fat content, a flaky texture and a delicate flavor. It is best suited for dry cooking methods like pan-frying, baking and smoking.

Tuna, with its bright red flesh and meaty texture, is one of the few fish that can be cooked to different levels of doneness, such as medium, medium-rare, etc. Bluefin tuna are used for sashimi and sushi. Yellowfin or Skipjack are canned dark tuna while albacore is canned white tuna.

Whitefish, a popular North American fresh water lake variety, are firm and sweet and have a moderate fat content. Whitefish can be grilled, baked or smoked.


Flounder has firm, lean flesh with a sweet, mild flavor. Moist cooking methods work best.

Sole, and all of its varieties, such as Dover , are actually flounder.

Halibut, one of the larger fish, has lean, firm, snow-white flesh. It is versatile for any cooking method.


Clams are harvested along the East and West Coasts of the U.S. The many varieties are cooked before eaten and typically used in soups, stews and sauces.

Mussels are found in ocean waters worldwide. They are best steamed in wine or in a seasoned broth.

Oysters are also found worldwide. Typically they are eaten raw, but can also be steamed or baked in the shell.

Scallops are almost always sold shucked, frozen, and vacuum-sealed. Sea scallops are larger than bay scallops. They can be prepared in any cooking method, however, if overcooked they will develop a rubbery texture.

Squid, commonly known as calamari, is typically sold breaded in the retail market. It should be prepared deep-fried.


Crabs are found along the North American coast and are shipped around the world in fresh, frozen and canned forms. There are many varieties, each with distinctive characteristics. King crabs are very large, which is why they are usually served with their legs which also contain abundant meat. Stone crabs, on the other hand, are generally available only as cooked claws. Soft-shell crabs are blue crabs harvested within 6 hours after the crab has shed its shell and are only availably mid-May through mid-September.

Lobsters have dark shells that turn bright red when cooked. Maine lobsters are cold water lobsters found along the Northeast Coast of the U.S. Warm water lobsters are found around the Bahamas and Caribbean. While there is edible meat in the tail and claw, only the lobster tail is typically sold in retail markets. Restaurants usually serve the whole lobster.

Shrimpare the most popular crustacean. They are typically packed raw, head-off, tail on but, are also available cooked, peeled and deveined. Deveining is the process of removing the digestive tract or “vein” from the body of the shrimp. Shrimp are sold in counts per pound. For example, shrimp marked “21-26” count means there is an average of 21-26 shrimp per pound; shrimp marked “U-10” means there are fewer than 10 shrimp per pound.

Cuts of Fish

Fish is available in a variety of forms in the retail market.

  • Whole as caught.
  • Drawn with internal organs removed.
  • Dressed with internal organs, gills, fins and scales removed.
  • Pan-dressed is dressed with the head removed. Small fish, such as trout, may still include the head. Pan-dressed fish are then pan-fried.
  • Butterflied is a pan-dressed fish that is opened flat.
  • Filet is the side of the fish only. It can be boneless or semi-boneless with or without the skin.
  • Steak is a cross-section slice that includes a section of the backbone. These are from large round fish such as halibut.