I took a fish cooking class the other day, at LA's New School of Cooking. Perhaps not surprisingly, we spent a big chunk class talking about how to buy fish -- because it's a more sensitive meat than chicken or pork or beef, and can go bad much more quickly because of its high moisture and protein content. Aside from overcooking, probably the number one mistake people make with fish is buying mediocre product and then storing it improperly. So here are a few ground rules on both buying and storing.
Things to smell for in a seafood market
The first thing you want to do when you walk into a fish market (or the seafood section of your grocery store) is take a whiff. Does it smell a little salty? Like the beach, perhaps? That's a good sign. Fish isn't odorless, and a fish market should smell like "a clean beach." However, if the "fish smell" smell is intense, that's a warning sign -- it could mean that the fish hasn't been stored properly, or the market isn't particularly clean. Also, look at the ice. You want to see the fish lying on beds of finely-crushed ice, not on cubes of ice, which can damage fragile filets of fish.
How to tell if whole fish is fresh
Buying a whole fish? The skin should be shiny, almost iridescent. If it's got a slimy-looking coating, that's OK -- it's natural. Just make sure the slime is clear, not cloudy. Also, look at the eyes. They should be clear and not sunken-in, which is a sign of dehydration. Make sure the fins aren't torn up. And don't be afraid -- if they'll let you -- to push on the fish with your finger. It should almost spring back from your touch, which is a sign that the meat is still full of moisture.
Looking for freshness in filets
Really fresh fish filets should be moist-looking and slightly translucent. They should be firm to the touch -- compact and dense. If it flakes, that's bad, a sign of dehydration.
How to store fish
Most home refrigerators aren't cold enough to keep fish in for long. The ideal temperature for storing fish is 33-34 degrees -- almost but not quite freezing. But there's a workaround you can use if you buy fish and aren't planning on using it for a day or two. First, unwrap the fish and then re-wrap it so it's not so tight in the paper. Fill a bowl with ice and put the fish, in its paper, on top of the ice, and cover the whole thing, bowl and all, with an upside-down colander. Put this is the back of your fridge, the coldest part. This is good for 48 hours of storage, max.
Then cook the darn thing! (Want some good recipes? I love the Cook's Illustrated website. These guys are like crazy food scientists, and they cook every recipe a dozen times a dozen different ways to make sure they're doing it the absolute best possible way. There's an annual fee, but it's worth it -- and they have a free trial.)