“It’s not always possible to ‘see’ that a lesser product has been substituted for another,” says Mary Snyder, FDA’s species identification expert. 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 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. Many seafood cookbooks also offer full color illustrations which 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, you may want to discuss the problem with the fish market manager where the product was purchased.
Sometimes regional names for fish are “made up” to make the fish sound better or of higher value, Snyder says. She gives the example of tilapia, a common imported fish that is also bred in the United States and other countries through aquaculture (on fish farms). Because it is also found in the Sea of Galilee in Israel, it traditionally has been called “St. Peter’s fish,” for the biblical fisherman of the New Testament. Importers have tried bringing it into this country labeled “St. Peter’s fish,” but FDA has informed them that it must be labeled tilapia.
Distinguishing salmon steaks and fillets from other fish is easy, due to their distinctive color and appearance.
Source: FDA Consumer Magazine