They are marketed under a number of regional names. Sometimes, FDA regulators must use laboratory verification such as identifying the fish scale and patterns, or isoelectric focusing, a technique that identifies a species by analyzing the pattern of proteins in the flesh. When charged with an electric current, the proteins form a unique pattern for each 7 species. The pattern from the species in question is then compared with the known pattern for that species, very much like comparing fingerprints. Many species have distinguishing marks or specific origins, and an informed consumer can watch for the marks or ask the fish market manager where the fish comes from.
Consumers can also check one of many well-illustrated seafood cookbooks.
These have information on what species look like, and how to tell the difference between substitutes and the real thing. Usually there's also information about the texture and taste of a species. If a product isn't as expected after it's cooked, FDA advises consumers to discuss the problem with the fish market manager where the product was purchased. To guide species identification, FDA maintains a seafood names list, which is being expanded this year to include shellfish. The list is used mostly by industry so it can uniformly label its products using FDA acceptable market names.