To get the best value for your money when buying seafood,
it's important to know what you're buying. Be wary of unusual
bargains--some seafood is seasonal. If there is a considerable
difference between the price of a fresh product and what you
are accustomed to paying, it could be that it is from the last
season's frozen inventory. Buy from a reputable dealer. And if
the fish you choose looks or smells different from what you
expect, discuss it with the fish market manager.
Look for firm, shiny flesh that bounces back when touched. If the head is on, the eyes should be clear and bulge, and the gills should be bright red. The fish should not smell "fishy"--it should smell like a fresh ocean breeze.
It's easy to miss the telltale signs of species substitution. Sometimes, taste or consistency is the only way to detect it. If you feel you have purchased something different from what was represented, tell your fish market manager.
Here's how to distinguish some common species:
Source: Excerpted from FDA Consumer, September 1993: Is Something Fishy Going On?