Tuna varieties include the bluefin, yellowfin, bonito, bigeye and blackfin. Ahi is the popular market name for either yellowfin or bigeye tune. All are members of the mackerel family and are found in tropical and sub-tropical waters around the world.

Tuna are large fish, weighing up to several hundred pounds each. Bluefin, the finest and most desirable for sashimi, are becoming very scarce because of overfishing. Regular canned tuna is usually prepared from yellowfin or skipjack; canned white tuna is prepared from albacore, also known as longfin tuna.

Pacific tuna that is frozen at sea to preserve its freshness is referred to as clipper fish. Any of these species may be found fresh or frozen, however. Tuna is usually cut into four boneless loins for market. The loins are then cut into steaks, cubes or chunks. The flesh has a deep red color. The dark, reddish-brown muscle that runs along the lateral line is very fatty and can be removed.

Tuna flesh turns light gray when cooked and is very firm, with a mild flavor. Tuna work well for grilling or broiling and may be marinated or brushed with seasoned oil during cooking. Tuna are often prepared medium rare to prevent dryness.

Red Snapper is an attractive, medium-sized fish with a firm texture and lean, white flesh that has a mild sweet taste. is also known as the American or northern red snapper. Although there are many members of the snapper family, only one is the true red snapper. Red-skinned rockfish are often mislabeled as the more popular red snapper or Pacific snapper, a practice that is currently legal only in California.

True red snapper has lean, pink flesh that becomes white when cooked; it is sweet flavored and flaky. They are sold whole or as fillets with the skin left on for identification. Red snapper may reach 35 pounds, but most are marketed at only 4 to 6 pounds (1.8 to 2.7 kilograms) or as 1-to 3-pound (450-gram to 1.3-kilogram) fillets. Red snapper can be prepared using almost any cooking method. The head and bones are excellent for stock

Swordfish take their name from the long, swordlike bill extending from their upper jaw. These popular fish average about 250 pounds (112.5 kilograms). Their flesh is lean and sweet with a very
firm, meatlike texture; it may be gray, pink or off-white when raw, becoming white when cooked. Swordfish are most often available cut into wheels or portioned into steaks perfect for grilling or broiling.

Mahi Mahi is the more commonly used name for dolphin or dolphin fish; this Hawaiian name is used to distinguish them from the marine mammal of the same name. (Dolphins and porpoises are marine mammals.)
Also known by their Spanish name, Dorado, mahi-mahi are brilliantly colored fish found in tropical seas. Mahi-mahi weighs about 15 pounds (6.6 kilograms) and are sold whole or as fillets. Their flesh is off-white to pink, lean and firm with a sweet flavor. Dolphinfish can be broiled, grilled or baked. The meat may become dry when cooked, however, so a sauce or marinade is recommended.

Grouper the grouper family includes almost four hundred varieties found in temperate waters worldwide. The more common Atlantic Ocean varieties are the yellowfin grouper, black grouper, red grouper and gag: the Pacific Ocean varieties are
the sea bass (also known as jewfish and different from the black sea bass) and spotted cabrilla.
Although some species can reach 800 pounds or more, most commercial varieties are sold in the 5- to-20 pound (2.2-to-8.8-kilogram) range. They have lean white flesh with a mild to sweet flavor and very firm texture. Their skin, which is tough and strongly flavored, is generally removed before cooking. Grouper fillets maybe baked, deep fried, broiled or grilled.

Sole are probably the most flavorful and finely textured flatfish. Indeed, because of the connotations of quality associated with the name, "sole" is widely used for many species that are not members of the sole (Soleidae) family.
Even though the FDA allows many species of flatfish to be called "sole" for marketing purposes, no true sole is commercially harvested in American waters. Any flatfish harvested in American waters and marketed, as sole is actually flounder.