Sold completely intact, exactly as they were caught

Round fish (e.g., salmon, trout, bass, mackerel) have a rounded rib cage, eyes on either side of their head, and swim upright. Round fish typically yield two fillets.

Flat fish (e.g., halibut, flounder, sole) have flat rib cages and both eyes on one side of their body, with that side always facing up. Flat fish typically yield four smaller fillets.

Drawn fish are whole fish that have been gutted, meaning their viscera (stomach, roe sacks, other guts) have been removed. Gutted/Drawn fish generally last longer than fish that are 100% Whole/In the Round, because the guts spoil faster than the meat.

Headed & gutted fish have had their viscera (guts) and head removed.

Dressed fish have had their viscera, head, tail, and fins removed. They have also been de-scaled.

Whole gutted fish with head and tail removed.

Steaks are portions of fish that have been cut across the body rather than along the sides. Often, but not always, they include a section of backbone.

Fish fillets are cut along the entire side of the fish, removing the meat from the spine and most of the bones.

Butterflied fillets are two fish fillets that have been cleaned like regular fillets, but left attached to each other.

Fish fillets, especially those from particularly large fish, are often cut into smaller portions to make them more manageable. A typical restaurant portion weighs 6oz, but larger or smaller filet portions are also sold.

Some large fish have portions of meat on their heads, separate from the fillet, that are of sufficient quality to be harvested and sold separately.

The fish skin is left on the portions. Skin on fish fillets & fillet portions are often used in pan seared fish recipes, so the skin crisps up, providing an attractive texture and presentation. If desired, you can remove the skin from skin-on fillets after you buy them. See How to Remove Fish Skin for the basic technique.

Skin removed prior to sale. Whether to leave round fish skin on is often a question of personal preference, the species being used, and the recipe being used. Flatfish skin is very leathery and generally considered inedible.

Many fish fillets have small, thin, flexible bones distributed along the side of the fillet. Generally, these are removed (usually with a pair of tweezers) prior to cooking and serving the fish. "Pin Bone Out" fillets have already had the pin bones removed.

Fish or fish portions that have been frozen within hours (usually 5 or 6 hours) of the firsh being caught. The fish are cleaned, processed, and frozen on the vessel that caught them. FAS fish have a reputation for being much higher quality than fish frozen much later, and even some fresh fish depending on how long it has been out of the water. In some cases, FAS fish may be more environmentally sustainable because it can be transported more slowly than fresh fish often by using lower-carbon methods (e.g., trains instead of jets).

The United Nation's Food & Agriculture Organization (FAO) has divided the world's fisheries into defined areas used for statistical data-gathering, the management of fisheries, and jurisdictional purposes. FAO 37, for example, indicates the Mediterranean and Black Seas.

MSC certification is a way of showing that a fishery meets international best practice for sustainable fishing. Fish and seafood from certified fisheries can carry the blue MSC label, assuring customers that what they're buying is sustainable.

NOAA Fisheries (aka National Marine Fisheries Service) is the office of the National Oceanic and Atmospheric Administration responsible for the stewardship of the nation's ocean resources and their habitat. The NOAA Seafood Inspection Program offers export certification services to facilitate exports of seafood products that meet the unique requirements of each importing country, and any other specific industry buyer criteria.