There's no mystery to determining if seafood is fresh; just look it over with a critical eye. Fish fillets and steaks should be bright, translucent and look moist, not dull or opaque. Dark-fleshed fish, such as tuna, should be bright, not brown. Whole fish should have shiny skin, clear eyes and moist, red gills.
If you're unsure, ask if you can sniff and feel the flesh. Fresh fish smells clean and briny like the ocean, not strong or "fishy." The flesh should feel firm to the touch, not soft.
Since fish deteriorates quicker than other proteins, keep an eye on how it is stored at the market. It must be kept iced at 32 degrees Fahrenheit with fillets and steaks stored on top of flaked or shaved ice and whole fish buried in ice. Pass on fish that is left sitting in water or melted ice.
Unless frozen, most shellfish is sold alive. Lobsters, crabs and crayfish should be lively, moving their claws and scuttling around their tanks. Clam, oyster and mussel shells should be tightly closed. And for fresh shrimp, check to make sure they don't have an ammonia odor or black spots.
Although we suggest seafood substitutions, the most important factor to consider is freshness. Always buy the freshest seafood possible. When choosing a substitution, look for fish with similar texture and fillets or steaks of similar thickness.
Fresh seafood is not always better than frozen. Seafood that is cleaned and frozen immediately can often be better quality than "fresh" seafood that has spent days in transit. Care in handling and freezing varies, so use an open mind and a sharp eye when judging the "freshness" of any seafood product, fresh or frozen.
Fish should be refrigerated as soon as possible and is best eaten the day of purchase. Optimum temperature for fish storage is 32 degrees and most refrigerators are about 40 degrees, so we recommend storing fish on ice. Set the still-wrapped fish in a colander filled with ice, and then put the colander over a bowl. As the ice melts, the water drains to the bowl underneath. You can also surround fish with ice packs.
Live shellfish should be kept in the refrigerator, but do not wrap them in plastic as they need to breathe. Loosely wrap them in a damp dish towel set in a bowl or pan.