Use your eyes and nose to help you discern quality and freshness. All fish should look moist and bright and have a fresh, clean scent. Steer clear of products with discoloration, dryness or even the slightest hint of an “off” aroma. Whole fish, in general, should look almost alive, with clear eyes; bright, intact scales and skin; and red, moist gills. To find the best-quality fish, start with a reliable fishmonger or the seafood department of a well-stocked food store with frequent turnover.
Lobster and Crab
Live crustaceans should move with some vigor when poked; any that are sluggish and apathetic have been in the tank too long. Lobsters should quickly snap their tails tightly under their bodies when lifted.
Ideally, buy live lobsters and crabs immediately before you plan to cook them, and go directly home from the market. When purchasing a whole cooked lobster, make sure that its tail curls, an indication that it was still alive when it was dropped into the cooking pot. If possible, avoid cooked crabmeat that has been frozen.
Choose firm, sweet-smelling fresh shrimp still in the shell when possible. Most shrimp sold has been previously frozen and thawed. You may do better buying still-frozen shrimp, since its quality is the same or better than thawed, and you’ll be able to decide when to use it.
Pass over shrimp with yellowing or black-spotted shells, an “off” odor, or a gritty feel. In general, avoid preshelled and deveined shrimp, as their texture and flavor will likely have suffered during the freezing process.
Clams, Mussels and Oysters
Always buy mollusks from reputable merchants who can vouch that they come from safe, clean, unpolluted waters. Fresh live mollusks in the shell have a mild, sweet smell. Their shells should be closed tightly and feel heavy with water; do not buy any that remain open when touched. A strong fishy or ammonium odor indicates they are no longer fresh, so pass them by.
Any oysters intended for eating raw should be bought fresh and shucked within a few hours of serving. When buying containers of shucked oysters, clams or mussels, check that the shellfish are plump and their liquor is clear, without a trace of milkiness.