Fish, having become nutritionally chic precisely when we can't afford it so often, remains slightly unfamiliar territory for many. But while many fish stores do nothing to overcome a common fear of fish shopping, some take the lead in labeling their fish with names and prices, in encouraging us to special-order monkfish or eel. When the thought of chicken fills you with ennui, and frozen fish fillets fail to make your juices run, turn to the accompanying directory of local fish stores. If you're in a porgy and croaker rut, branch out. Wrap a white fish fillet around an oyster stuffing, for an elegant alternative to a roast beef dinner. Or steam sea bass in a Chinese black bean suace with less effort than it would take to make meat loaf. Meanwhile, learn the rules for fish shopping, to stretch your fish dollar and assure yourself of freshness and quality.

ONE OF the best values on the market in the last year has been the tiny bay scallop (also called a calico scallop), which is caught in North Carolina and Florida. Normally bay scallops are much more expensive than sea scallops, but because of their abundance this year, that price differential has been reversed. And because of their long shelf life, three to four days in a well-iced seafood department, scallops are a good buy even in supermarkets. (However, any seafood will perish quickly in a home refrigerator and should be eaten the same day purchased.)

Size and price tend to go hand in hand. A 2- to 5-ounce flounder fillet may be cheaper per pound than a 6- to 8-ounce fillet, and a jumbo shrimp will cost more per pound than a small one. When the difference is only cosmetic, buying small can be smart.

When shopping for shrimp, don't be misled by words like "jumbo" and "large," because shrimp superlatives aren't regulated. What one store calls "jumbo" another calls "large" and yet another calls "super jumbo." Ask instead what the "count" is -- how many shrimp there are per pound. Loosely translated, an under-15 count is jumbo, 15 to 25 large, 35 to 40 or so medium, and 40 to 60 small. Flavor depends less on size, however, than on where the shrimp came from, when they were caught, and how well they were handled in the interim.

According to Melvin Spitz of Gloucester Lobster, the smart customer will buy "cull," or one-claw lobsters. After all, you're paying by the pound, at a lower price per pound, and you're getting a higher proportion of the more desirable tail meat.

It pays to patronize a fish dealer you trust. For example, some dealers sell any red-skinned fillet, including ocean perch, as red snapper. Though ocean perch is itself a very good fish, it does not taste like red snapper and has nowhere near the same market value.

When you buy crab meat from a retailer, ask him to invert all of it onto the lid of the tin so you can see how consistent the pack is. Don't assume that because you see six big lumps through the transparent spot on top of the lid that you're getting an excellent grade. Many packers "top off" the crab meat so that larger lumps are exposed and smaller pieces are concealed at the bottom. Maryland and Virginia packers tend to produce a more consistent grade of crab meat than Carolina packers. Texas and Louisiana crab meat, while well picked over, is usually boiled rather than steamed, and may taste washed out to local palates, though the difference may not be discernible in some recipes.

Fatty fish freezes better than lean, but it's surprising what you can put in a freezer. Instead of buying mussels for $1.50 a pound, you can often buy a bushel (50 pounds) of them for $15 to $20. Remove what you don't use immediately from the shell, pack the uncooked mussel meat in meal-size freezer bags and freeze it for use in a lovely mussel soup some cold winter's evening.

Fish terminology is so ambiguous that you should never hesitate to ask questions. Other customers in the store generally won't know any more about the fish than you do, and will be happy to eavesdrop. After a while, you'll become savvy enough to know not only that American fillet of sole is generally flounder (a perfectly good fish) but also that gray sole carries a higher price tag than lemon sole (though both are flounders), and many people won't find the difference worth the premium price. Dover sole, the famous one, can be air-shipped fresh from England but is usually sold frozen.

Now for the cooking:

ROLLED FISH FILLETS WITH OYSTER STUFFING (6 first-course servings, 3 main-course servings)

This recipe looks elegant and tastes very special, even to confirmed fish haters. The recipe calls for any fish fillet; I used cod because it was cheap, and it worked beautifully. Clean tuna cans with both lids removed make perfect molds. One advantage of using them instead of a muffin tin is that you can mold the fish rolls inside them on a baking dish, remove them when you've finished cooking the fish, and bring the baking dish to the table with the fish rolls undisturbed and intact. About 1 1/2 pounds of firm fish fillets 3 tablespoons butter or margarine, plus enough for buttered bread crumbs 3/4 cup chopped mushrooms A few drops of onion juice (squeeze a piece of onion in a garlic press) 1/4 cup flour 1/2 cup heavy cream 12 fresh oysters, shelled Salt, pepper, cayenne and mace, to taste Approximately 1/2 cup of bread crumbs

Trim fillets into neat, thin pieces that can be coiled inside 6 buttered muffin rings, large cupcake tins or empty, lidless tuna cans. In a saucepan, melt butter and add chopped mushrooms and onion juice, cooking for 1 minute. Stir in the flour. Stirring constantly, gradually add the cream, and as soon as the mixture is very hot, mix in the oysters. Season to taste with salt, pepper, cayenne and mace.

Fill the muffin rings (lined with fish) with the oyster mixture and cover with foil. Bake at 375 degrees for 20 minutes or more (10 minutes per 1-inch diameter of rolled stuffed fish), then remove foil and sprinkle each serving with buttered bread crumbs. Bake uncovered until the crumbs are a golden brown. Slip the rings off and remove the rolled fillets to a hot platter with a spatula. From "The Free Food Seafood Book" by Peggy Ann Hardigree.

CHINESE STEAMED FISH WITH FERMENTED BLACK BEANS (1 to 2 servings)

Nothing could be simpler to prepare than this tasty whole fish. Salted, fermented black beans are available in Oriental stores and are worth having around the house. If you use a fish larger than the one called for in the recipe, simply increase the other ingredients proportionately. 1 fresh fish, about 1 pound (sea bass, striped bass, rockfish or sea trout) 1/4 teaspoon salt 1 tablespoon shao-sing wine, sake or dry sherry 1 tablespoon fermented black beans 2 tablespoons oil 1 tablespoon finely shredded ginger 2 tablespoons chopped scallions 1 tablespoon chopped or shredded fresh red chili peppers (or dried or pickled red chili peppers, or chili paste) 2 tablespoons soy sauce

Scale and clean fish (the fish store may already have done this), rinse it in cold water, then pat dry inside and out with paper towels. Score both sides of fish by making three diagonal cuts about 1/2-inch deep. Rub inside and out with salt and wine. Place fish on a heatproof plate large enough to hold the fish but small enough to fit inside your steamer -- or place it on the rack of a steamer. (Don't let this part be a problem to you: If you put the fish in an electric skillet with half a cup of water, the results will be fine.)

Rinse black beans with water and drain. Mash beans slightly. Heat oil in a wok or small saucepan. When oil is hot, add fermented black beans, ginger, scallions and chili peppers. Cook mixture in hot oil for a few seconds, then add soy sauce. Remove from heat and pour mixture over fish, spreading it over the entire fish.

Cover pan tightly and steam fish for 10 minutes. Remove fish from pan and serve immediately. From "Chinese Seafood Cooking" by Stella Lau Fessler.

GROUPER BAKED IN LEMON CREAM (4 to 6 servings)

A hot oven melds the lemon juice, onion and cream into a rich sauce as it cooks and moistens the fish in this delectable recipe. 1 skinless grouper fillet (about 2 pounds) 1 cup heavy cream 5 teaspoons lemon juice 2 tablespoons minced onion 1/8 teaspoon salt 1 egg yolk

Wipe fish with damp cloth; arrange in a greased, large, shallow baking pan.

In a bowl, combine cream, lemon juice, onion and salt and mix well. Pour evenly over fish. Bake at 400 degrees, uncovered, until fish flakes when prodded with fork in thickest portion. For a 1-inch piece of fish (measured in thickest portion), allow 10 minutes; adjust cooking time proportionately for fish of different thicknesses.

When the fish is done, remove pan from oven. With a wide spatula, lift fish from hot cream mixture; drain briefly and transfer to a warm serving platter. Cover and keep warm.

In a small pan, beat egg yolk slightly. Using a wire whisk, beat a little of the hot cream mixture into the egg. Then pour remaining hot cream mixture into egg mixture, beating constantly. Cook egg and cream mixture, stirring, over low heat until slightly thickened, about 5 to 10 minutes, but do not boil. Pour evenly over fish and serve immediately. From "Sunset Seafood Cook Book."

RUTH SPEAR'S CRAB CAKES (4 to 6 servings)

Next time your supermarket has crab meat on sale, buy a can and make these crab cakes, which even with canned pasteurized crab meat are much better than those you'll find in most restaurants -- and they're a snap to make. 2 cups backfin crab meat 1/4 cup milk 2 tablespoons finely chopped parsley Salt, to taste 1/2 cup fresh bread crumbs 2 eggs, well beaten 1 teaspoon worcestershire sauce 4 tablespoons butter Lemon wedges Tartar sauce (recipe below)

Pick over the crab to remove shell and cartilage. Blend crab with the milk, parsley, salt, bread crumbs, eggs and worcestershire sauce. Shape into 4 to 6 cakes, fry in butter on both sides until golden brown. Serve with lemon wedges and tartar sauce. From "Cooking Fish and Shellfish" by Ruth A. Spear.

RUTH SPEAR'S TARTAR SAUCE (Makes about 2 cups)

The recipe variations for this classic accompaniment to fish of all kinds are endless, so this is not the recipe for tartar sauce -- only a recipe that I like very much. Half this recipe will do for the crab cakes above. 2 cups mayonnaise 3 tablespoons onion, finely chopped 2 teaspoons lemon juice 3 tablespoons dill pickle or gherkin, finely chopped 2 tablespoons parsley, finely chopped 2 tablespoons capers, minced and drained 1 teaspoon dijon-style mustard Salt and pepper to taste

Whip the mayonnaise lightly and add the remaining ingredients. Refrigerate, covered, for 1 to 2 hours before serving. Serve with fried, broiled or poached fish, or fried shellfish.

Variations: Replace the onion with 3 shallots, finely minced, or reduce the amount of parsley and add minced tarragon and minced chervil. If you like tartar sauce on the sweet side, add 1 teaspoon of sugar. Or add 1 finely chopped hard-cooked egg to the basic recipe to make a gribiche sauce.

The Tadich Grill, a famous San Francisco fish restaurant, serves a superb tartar sauce, the secret of which is the addition of mashed potatoes. It makes the sauce smooth and less rich and oily. Try adding a quarter-cup of plain mashed potatoes to the above recipe. From "Cooking Fish and Shellfish" by Ruth A. Spear.

PAN-FRIED RED SNAPPER WITH GINGER, GARLIC AND TANGERINE SAUCE (1 to 2 servings)

This simple dish is both festive and tasty.

For marinade: 2 teaspoons pale dry sherry 1 tablespoon fresh ginger root, finely minced 1/4 teaspoon salt 1 fresh red snapper, 1 1/2 pounds (whole, scaled and cleaned)

For cooking: 2 tablespoons flour 4 tablespoons oil 2 scallions, chopped into pea-sized pieces, including green part 2 teaspoons fresh ginger root, finely minced 1 tablespoon garlic, minced 1 piece dried tangerine peel, soaked in hot water 15 minutes or until soft, and minced (about 1 tablespoon)

For sauce: 2 tablespoons thin soy sauce 1 tablespoon black soy sauce 2 1/2 tablespoons pale dry sherry 1/2 teaspoon sugar 2 tablespoons water

Rub sherry, ginger and salt inside and outside fish and refrigerate for 30 minutes. Then sprinkle seasoned fish with flour. Heat wok over high heat, and swirl in oil. When oil is hot, put fish in wok. Fry over medium-low heat until both sides are golden brown (about 12 minutes each side). Remove fish and put into a warm oven to keep hot.

Reheat oil left in wok. Slightly brown scallions, ginger, garlic and tangerine peel. Combine soy sauces with sherry, sugar and water, and add to wok. Heat to boil. Return fish to wok and baste with sauce. Put fish on an oval platter and spoon sauce over it. Serve hot at once. From "The Classic Chinese Cook Book" by Mai Leung (Harper & Row).

COTTAGE SALMON MOUSSE (6 servings)

We tried this recipe because we were curious how good a recipe could taste made with canned salmon (we tried it with canned chinook). Not bad at all, and the nice thing about this one is that most of the ingredients are items you might already have on hand. It's a rich-tasting mousse, which really benefits from the light sauce. 15 1/2-ounce can of salmon 1 envelope unflavored gelatin 1/4 cup cold water 1/2 cup boiling water 1/2 cup mayonnaise 1 tablespoon lemon juice 1 tablespoon grated onion 1/2 teaspoon hot pepper sauce 1/4 teaspoon paprika 1 teaspoon salt 1 tablespoon chopped capers 1/2 cup heavy cream 3 cups cottage cheese (optional) Watercress, sliced lemons, and/or salmon roe, for garnish Dillweed and sour cream sauce (recipe below)

Drain salmon, remove skin and bones, and finely chop salmon. Set aside. Soften gelatin in cold water, add boiling water, stir until dissolved and let cool. Add mayonnaise, lemon juice, onion, hot pepper sauce, paprika and salt to gelatin, and mix well; chill to consistency of unbeaten egg white. Add salmon and capers and beat well. In a separate bowl, whip the cream, fold in salmon mixture, and turn into a 2-quart oiled fish mold if you have one. Add cottage cheese to top of mold (we didn't try this part). Chill until set. Unmold on a serving platter and garnish with watercress, lemon and salmon roe. Serve with dillweed and sour cream sauce. From "The Salmon Cookbook" by Jerry Dennon.

DILLWEED AND SOUR CREAM SAUCE (Makes 1 cup) 1 cup sour cream 1 teaspoon dried dillweed 1 tablespoon wine vinegar 1/4 teaspoon salt

Mix ingredients well and let sit, chilled, until dill flavor registers in the sauce. From "The Salmon Cookbook" by Jerry Dennon