The invisible restaurants. Ask people about their cities' good seafood restaurants, and they are likely to answer, "We don't have any good seafood restaurants. In fact, that's just what we need." Mention Joe's Stone Crab or Tadich Grill and they remember. But not before.

Although Americans are eating more fish than ever, it is not rash to generalize that the average American seafood restaurant is just plain awful. Some of the best places to eat fish are not seafood restaurants, but just good restaurants --French, Italian, Chinese or steakhouses.

Maybe the problem is that all too often seafood restaurants are tourist places, where the clientele need not be pleased enough to return.

Still, great ones have survived, and perhaps greater ones are in the making. Although seafood supplies are being depleted--lobster threatens to join sturgeon as an endangered species--inventive minds are preoccupied with finding new sources. The West Coast is cultivating Long Island oysters, belons and crayfish. Sturgeon is being raised experimentally. And abalone, at more than $20 a pound, is being farmed.

We are learning to appreciate delicacies we once considered trash--sea urchins, mussels, periwinkles. But all that increased consumption still adds up to only 13 pounds of seafood a year per person. Given the overripe or frozen, overcooked and heavily breaded versions we have been so often served, no wonder.

But there is some good news: the fish aren't just jumping, they're flying--coast to coast. As a result, Americans are discovering what fresh fish means, and they like what they are learning.

Here is what is being served along America's coastlines, in the grand old and the grand new seafood restaurants.

SAN FRANCISCO

In San Francisco you start in the fish business early. For Tom Thompson of Achille Paladini Seafood Co., it was age 10, picking crabs at Fisherman's Wharf. Thompson, who has seen plenty of change in the West Coast seafood business, continues to observe: Squid is a growing field, and will be an even bigger market when a new squid-cleaning machine, invented at the University of California at Davis, is on the market; wholesalers now sell 1,500 pounds of shark a week, but much of it goes on restaurant tables as swordfish; prawns are being priced out of the market; fresh scallops are becoming popular and custom- cutting of fish is disappearing.

The big trend is fresh fish, especially in restaurants, a trend that Thompson notes demands quality control. Temperature is important. Fish kept at 38 degrees can have a 7- to 10-day shelf life. In addition, fish should be washed when it is caught and gutted as soon as possible to remove parasites and forestall enzyme action from the stomach. The way it is caught is important, too, although which method is best is a matter of controversy. Thompson prefers fish caught by trolling, which produces no bruises. Others prefer netted fish--you can spot those by the netting lines on the skin near the head.

The quality of the fish depends, too, on its life history: what it has eaten, how it has eaten, what kind of parasites might have been eating it, what part of its spawning cycle it was in when caught and how it was caught.

A good fish buyer can tell those things and demands the best. Take Tadich Grill, for instance, one of San Francisco's oldest and most respected seafood restaurants. No wonder the line is long at 11:30 a.m., when Tadich opens. The restaurant began with the gold rush in 1849 and has stayed golden through several moves. At Tadich, you can eat at the long wooden bar or in a private dining room. Like most American classic seafood restaurants, the waiters are cantankerous, swift and prone to let their soft hearts show in some unexpected way.

Tadich is as good a place as any to learn the law of ordering at an American seafood restaurant: keep it simple and local. Charcoal-broiled petrale: wonderful. Charcoal-broiled swordfish: unbeatable. Cioppino: the fish fine but the broth too herbed. Broiled sturgeon with mushroom sauce: a brown gravy embarrassment, the sturgeon cut unevenly and therefore cooked unevenly. And Coney Island clam chowder: well, you should know better.

Many people prefer Tadich to Sam's, San Francisco's other old and famous seafood restaurant. Tadich's tartar sauce, made with mashed potato, is reason enough to prefer that restaurant. But even so, I give the edge to Sam's, a relative newcomer, opened in 1867. Like Tadich, it has dark wood trim and brusque but endearing waiters; the chef has been there 50 years, the vegetables are fresh, and the prices are lower. Sam's may consider rex sole and sand dabs its specialty, but I prefer the petrale I ate there: four fillets dusted lightly with paprika and grilled on mesquite wood. The halibut was no slouch, but the squid steak was better skipped. Sam's had tiny, sweet Olympia oysters, the size and juiciness of grapes. It spends $45 a day on mesquite wood for its grill.

Mesquite wood is an enigma, but a very popular one, brought from Mexico. Nobody in California would be caught grilling fish on anything else. Some say it is excellent for grilling because it is not treated with chemicals. Others say it gives fish a special flavor, or that it burns hotter or less hot or more evenly or whatever. Though mesquite-grill restaurants are popping up all over California, Sam's has been using it for at least 50 years.

Hayes Street Grill could become the Sam's or Tadich of tomorrow. It is a contemporary seafood restaurant, with its all-fresh fish cooked on mesquite. The petrale is served on the bone but skinned. There was no paprika --that's yesteryear's style-- but, instead, a choice of sauces: beurre blanc, b,earnaise, caper, fresh herb, Szechuan peanut. The french fries come with their skins on, and the sourdough is good. While the seafood list is not as extensive as the old timers', it offers successful inventions, such as lightly warmed charcoal- broiled oyster brochettes, homemade sausages, marinated vegetables, clever soups and desserts worth noticing, such as cr,eme brul,ee.

In Chinatown, the fish shops are like alchemists' laboratories that turn the most unlikely things into food: huge fish heads, dried flounder, live frogs, giant goldfish, fish pastes destined for fish cakes, slithering eels and prehistoric-looking turtles. And these shops have the reputation for the freshest rock cod, shrimp and sea trout if cuttlefish isn't your meat.

From extensive French restaurant menus to the tiny marble counter at Swan Oyster Depot--which for 70 years has served hurried lunches of soup, tiny local fresh shrimp and oysters on the half-shell doused with vinegar from the owner's own barrels--San Franciscans are fish eaters.

LOS ANGELES

Los Angeles is turning out fish restaurants faster than Grade B movies. And there are tourist sushi bars and suburban sushi bars and chain sushi bars-- even a guidebook to sushi bars. In California there is even crab sushi with avocado. (No alfalfa sprouts yet.)

That's just a start.

Los Angeles is crossing the fast-food chain restaurant with the fish market to breed seafood grill restaurant chains. Seafood Broilers has 10 branches around Los Angeles and three in San Francisco. You go past the retail fish counter to a carpeted dining room with a glass-walled grill room and then choose your filleted fresh fish (seven to 10 choices each day) to be grilled on mesquite, either plain or with paprika and seasoning salt, and served with grilled potato, pilaf, coleslaw or cherry tomatoes. Nothing is fried. The restaurants make their own clam chowder and tartar sauce, and cut their own fish. Most grilled fish are less than $6 at lunch, $7 to $9 at dinner. The big sellers in America are shark, snapper, trout, ling cod and petrale.

The chain's success is mirrored in the competition: Enterprise Fish Co. (two branches), Castagnola Fish Shops (nine branches), Fish Kitchens (three branches), Monterey Canners (five branches), Hungry Tiger (16 branches).

In Los Angeles, you've got to have a gimmick. At Belmont Pier, the waiter brings the "menu tray," a flip-top display of fresh fish. You choose, then specify broiling, poaching or saut,eeing, and your seasoning (lemon, garlic, rosemary, basil, ginger, capers, mushrooms) and your sauce (white wine, Spanish, provencal, mustard, b,earnaise, veronique). And when it arrives, the plate is so hot that the fish has overcooked and the vegetables have been singed en route from the kitchen.

Michael's, a starlet of a Santa Monica restaurant, does a lot with seafood. The fish-- very fresh--is grilled to a crusty surface and rare interior, and sauced with fresh coriander and white wine (the waiter even specifies the grape variety of the wine). Tiny, briny Northwest oysters arrive just warmed and tossed with pasta. Salmon and spinach are layered in puff pastry. Michael's is the place to spot trends: large white plates with food artfully arranged in a vertical rather than circular design; warm salads wilted just so they don't crunch; beautiful young men acting as waiters, reciting the daily specials as if they were lines from a porno flick; an owner-host abrasive enough to remind you what a rare privilege it is for you to get a table; prices as imaginative as the food ($7 for an appetizer portion of pasta).

In Los Angeles, I sampled only one restaurant that met my oceanic expectations. Mon Kee's Chinese seafood restaurant is hard to find; 679 Spring St. seems to be surrounded by one-way streets leading away from it. Inside, it is just the standard Chinese place. But a fish tank with live Maine lobsters and Dungeness crabs looked promising, and the long Cantonese menu was downright enthralling: eight kinds of hot pots, 10 kinds of steamed whole fish, rock cod prepared 14 ways, lots of eel, crab, clams, frog, conch and sea cucumber, 17 shrimp preparations and 15 squid. Skip the abalone; the small ones cost $4 each for a couple of bites' worth and taste like marinated rubber bands. On the other hand, Mon Kee's stir- fried large whole shrimp with special salt are deep-fried with their heads on (and no batter), then saut,eed in a very peppery salt with scallions. The result is smoky and crunchy outside, so delicious you eat the shells. And red rock cod--only $8 for a fish of sumptuous size--was steamed with a faintly sweet and sour broth seasoned with scallions, ginger, garlic, coriander leaves and sesame oil. After the waiter boned it, he splashed over it a dark sauce that tasted extraordinary and turned out to be the chef's own homemade "soy sauce," for which he boils a half-dozen kinds of vegetables for hours until they are concentrated, and combines it with soy sauce.

Los Angeles reminds me constantly that I can't do it all. Even among local restaurant buffs nobody gets to visit, say, Scandia and Gladstone's and all the other ones people have heard about. Too much remains left undone. The chef at La Toque was sick when I was there, and the one at Ma Maison had left.

It is a big city, with enough disappointment to go around.

SEATTLE

In Seattle you are either damp or wet. That sounds depressing or uncomfortable only if you haven't been to Seattle. Weekdays are for passing the time between fishing trips.

Salmon are well cared for, treated almost as citizens. When the salmon released by the aquarium two years ago returned last fall, they were given a hero's welcome by the local newspapers. Salmon in Seattle is caught, bought and sold in every imaginable quantity and form, most of which can be seen at the Pike Place Public Market.

Opened in 1907, Pike Place, like many city markets, almost didn't survive. In recent years it has been revived by crusading city lovers who campaigned successfully to preserve it as a seven-acre historical district. The market, hanging over Seattle's Elliott Bay waterfront, has lush produce--white and golden chanterelles, tiny artichokes, Swedish blue potatoes, 6-inch apples--a Scandinavian deli, roasted rabbit, brioche, Malaysian noodles, pizza and no chain stores at all.

Most important, though, is its salmon. There are five species, and the ruler of them is king salmon, which, one discovers at the Pike Place Market, can be pink or white, but pink usually sells for a higher price. Salmon are piled like cordwood on Pike Place counters, but so are rock clams, huge red Dungeness crabs (virtually always frozen), catfish, rex sole, black cod, big purple sinister-looking sea urchins and those giant grotesque gooeyduck clams, which are inevitably the subject of Seattle's obscene jokes.

The market provides the wherewithal for a standup mollusk feast at Emmett Watkins' Oyster Bar, a mere corner of a shop where you can take a break with Quilcene or Minterbrook oysters and a glass of beer--preferably the fresh and hops-rich Henry Weinhard brew. Watkins' bar, which is only three years old but looks centuries worn, is likely to have available the cultivated Wescott Bay or Pacific belons, smoked salmon served with havarti cheese, seviche made with cod and a local concoction called mezzo-mezzo, which is a startling soup, half gazpacho, half clam chowder.

Anybody who thinks of Seattle as a bastion of tradition is swimming in the wrong lake. At Seattle's Japanese supermarket, Uwajimaya, there are self-service refrigerated counters offering fish heads wrapped in plastic, gooeyduck tempura, raw squid sliced and packaged in plastic meat trays with three sauces and prepackaged sashimi on a bed of lettuce, garnished with a plastic flower.

Annie et Robert, a French- Japanese restaurant lists among its appetizers terrine du jour, sushi and gooeyduck a la bourguignonne--with chopsticks. Its rack of lamb combines French mustard with Japanese wasabi; its New York strip steak is marinated with fresh water chestnuts, and its special salmon is stuffed with duxelle of chanterelles, sauced with a butter of sea urchin and salmon roe and garnished with lotus root.

Annie et Robert, like other respected Seattle restaurants, serves fish superbly. In fact, if one uses Seattle's most extravagant restaurant--The Other Place--as an example, the fish can be better than the restaurants. Whereas Annie et Robert is expensive--averaging $15 for main dishes at dinner, $7 at lunch--The Other Place is exorbitant. A two-course dinner costs $19 to $28. It is an impressive contemporary dining room on two levels, with the green and dark wood prevalent in Seattle. Its wine list is overwhelming. But what saves The Other Place from dissolving into a sea of awkward showiness is its fish. The waiter is slow, but the salmon is as smooth as ice cream. The poached sable came cold-- twice--but was delicious anyway. One might dismiss The Other Place as a bad joke of almost-raw vegetables and sandy lettuce, all flourish and no finesse, except for the fish.

McCormick's looks like a fernless fern bar, and, with bentwood chairs and black leatherette banquettes, it could be the setting for a cigarette ad. But in addition to burgers, steaks and seafood it lists two dozen fresh seafoods available, a dozen appetizers and two dozen entrees. It serves its delicious tiny shrimp already mixed with cocktail sauce, which seems a waste of their delicacy. But it also reminds you how flavorful those small West Coast mussels can be. And though it gets carried away with brandy-cream-peach sauce or onion-mustard-wine sauce, its fish are pure velvet, the black cod falling into great silky slabs with a fork, the salmon buttery and soft.

Salmon here and mussels there were revelations in Seattle; but the urge remained to try a full feast of Northwest seafood. So it was arranged, a half-hour away from Seattle, at a small rustic-nouveau restaurant with the Northwest Indian name, Mukilteo Caf,e. The young owners of the caf,e, which was still in its infancy, kept the knotty pine dining room uncomplicated in decor --the elaboration was on the plate. Scallops bonne femme, as soft as butter, in a nut- brown cream sauce; smoked black cod--salty but silken-- in a sauce mousseline; oysters prepared like rumaki, stuffed with water chestnuts and wrapped with bacon. The most delicious course was nonseafood: cream of celery soup "to cleanse the palate," as the ma.itre d'h.otel joked. We shared four main courses: a mild and pearly white king salmon; a grilled sturgeon of elegant flavor, cut thick so the juices were retained in the grilling; thresher shark baked in parchment with leeks, a bit tough but as flavorful as swordfish; and an extraordinary king crab, removed from the shell, flattened and cooked in milk with shallots and capers. Fresh crab legs are a continent away from the frozen ones, their sweet and delicate flavor preserved. A parade of Northwest wines, fruity and a bit sweet, accompanied the courses, the most interesting of them being a clear and golden Hinzerling Ash Fall White, grown in the ashes of the Mt. St. Helens eruption. It was a meal that pressed a choice: was it time to leave Seattle or stay forever?

NEW YORK

Fish sellers were afraid of going out of business when the pope declared that Catholics need not eat fish on Friday, said Mike and Louis De Martino, but instead people went from eating fish just on Friday to eating it five days a week. And since Dwight Eisenhower's heart attack focused attention on fish as low-cholesterol food, the fish business has escalated.

This was explained at 6 a.m. at Manhattan's Fulton Fish Market. Louis and Mike DeMartino were returning to the market for the first time since they had sold their highly successful 70-year-old fish business the previous February. The De Martino brothers started in the fish business when they were children. Their father taught them that sanitation came first, then quality, and only after that price.

They also learned how to buy the best fish, a lesson that takes years, decades. Always buy "the top of the boat," they insist--the fish that were last caught. They are experts who can tell which scallops are from Florida ("good eating but not as good as Cape or Long Island scallops"), which bluefish from New Jersey ("oily, because they throw a lot of junk fish into the water in New Jersey") and which from Carolina (fattier). They point out the Connecticut lobsters (the shells are softer, the meat watery) and those from Nova Scotia (any over six pounds, which can't be shipped out of Maine). And they can estimate which day a fish was caught, with just a look and a poke.

The De Martinos know all the tricks of the trade: the hake that is sold for cod; the croaker, grouper or tilefish that is passed off as bass; the snapper that has been washed with salt to try to hide its high smell. And they have definite preferences, say for gray sole.

All fish from colder water is firmer and better eating than that from warmer water, they declare, but red snapper and kingfish are exceptions. Louis prefers his salmon netted rather than trolled, because it is likely to have been alive until brought in. Pink swordfish is female, and sweeter than white swordfish. Some say too sweet, they add. As for the growing popularity of king crab legs during the past 20 years, Mike sniffs, "The butter sauce on it is the only thing you taste."

The De Martinos have opinions on fish purveyors as well. The Korean fish shops springing up in New York are "really something," says Mike. He praises the Grand Central Oyster Bar, whose buyer is at the market everyday buying only the tops. The same goes for Sea Fare of the Aegean and Gloucester House. But his favorite is Sweet's, and Sloppy Louie's is a must.

Sloppy Louie's is just across the street from the Fulton Fish Market, filled with long tables where everyone sits elbow-to- elbow. Posters with the day's catch are tacked on the mirrored walls. Oysters on the half-shell are $2.60, served with a bowlful of lemon wedges, oyster crackers and bread that reminds you you're not in San Francisco. But the waiters are the same: graying, brusque, but taking good care of you without letting you know they care. Sloppy Louie's is the kind of place where the market men call ahead to have their thick swordfish steaks put on the fire so they can hurry in to eat then rush back to work. And they expect to be served the best fish, the best oysters, the freshest fried clams. The fish chowder is overseasoned and floury, but homey. The fried foods are heavy, but hot and crisp. The prices are reasonable, and the portions forbid you to leave less than full.

Around the corner is Sweet's, the restaurant that draws the city hall crowd. Most fish dishes here are $2 to $4 more than at Sloppy Louie's, but if you have never understood the charms of Manhattan clam chowder, Sweet's is an education. The tomato broth is buttery and subtle, herbed and vegetable-studded, but does not drown the taste of the clams. The fish are pristine, broiled with a fine sprinkle of crumbs. Don't accept anything less than the best here (we sent back a watery, stale lobster cocktail) because here the best is indeed available.

As fine as New York's old market restaurants may be, they are variations of the mode, no better or no worse than Tadich or Sam's in San Francisco. But outside of New York there is nothing quite like Ratner's kosher dairy restaurant, where the fish dishes of last century's Eastern Europe are listed on a laminated plastic triple-folded menu, and the cloth napkins look as if they had been stomped. Everything is served in hunks (the iceberg lettuce, the half-onion to slice yourself for your bagel and lox) and is sweet (the pickled herring, the gefilte fish). But the gefilte fish is real, fluffy and made with challah rather than matzo meal. The chopped herring is pungent, the smoked sable satiny, the whitefish cleanly smoky, if a bit too firm. Ratner's serves dishes that would otherwise slip into history: pickled or boiled whitefish or carp, salt herring fried in an eggy batter and served with nearly melted onions.

The Grand Central Oyster Bar is the quintessential seafood restaurant and the quintessential New York restaurant. It has at its command 10 kinds of oysters on the half- shell, the prime swordfish of Block Island, salmon from the North Atlantic, lemon sole from Nantucket Sound, the best of everything that can be flown in from everywhere. It need do nothing but serve it plain--superbly plain. The Oyster Bar smokes its own salmon, sturgeon and trout, concocts Russian sturgeon stew (solianka) and Belgian fish stew (waterzooi). Its oyster pan roast is bound to have a novel or poem devoted to it before long. Fancy cooking is not the Oyster Bar's strong suit. The clam chowder, for instance, is a bore, the french fries flabby and tough. It is the place to swtart with six different kinds of oysters, taste extraordinary broiled sordfish or some fish you've never had before--or just tiny pnd, with

beerfect steamers, all with a California white wine from a list seldom equaled. Grand Central Oyster Bar, one might argue, lacks two important assets: it has no sea view; it isn't near a seafood market. It is, for heaven's sake, the basement of a railroad station. But that's part of its wonder. The arched brick ceiling, the endless counter, the subterranean architectural authority of those handsome rooms and the rumble of the trains are as effective as any foghorn or ship's bell.

Even a New Yorker can't keep up with the local restaurants' ups and downs. So Hisae's Lobster House, rumored to be of interest, was just "The Lobster House," having cut its ties with Hisae's, and showed how easily New American Cooking can go wrong. Everything had too much on it. The swordfish was under an inch of snow peas and green peppers. Lobster and shrimp were buried in quicksand-thick sauces. Tilefish was under a solid armor of browned garlic. Said one diner, "It is as though they don't trust the fish."

We trust John Clancy, however. Teacher and cookbook author, now restaurateur in a step-down SoHo fish restaurant bearing his name, he serves mesquite-grilled fish-- the salmon was smoky, moist, sparkling fresh--and a few daily choices of saut,eed, stewed and sauced seafoods of invention and excellence. The shrimp are juicy, with some bite, perhaps in a light dilled mustard sauce. His fish stews may show a heavy hand with herbs, but the seafoods in them are impeccable. Clancy serves tender clam bellies in a gentle r,emoulade, cures a respectable gravlax and finds unusual-- though expensive--oysters. And he cooks oysters superbly, not overwhelming them in their saucing or stuffing. Delicacy may turn to blandness in his soup. But no matter; this is a delightful restaurant, small and refreshing, its walls off- gray, its paintings chosen by an educated eye. Tables are well spaced and set with lovely floral plates. Huge bouquets of flowers are set in glass globes. The menu is small, the prices are moderately high, the wine list and accompanying vegetables are carefully selected. And to understand the finale, one must remember that John Clancy's reputation as a pastry chef is no less than that as a fish chef. Consistent excellence from the flourless chocolate cream roll to the lemon tarts one would expect, but few besides Clancy could make me willing to eat another, yet another, carrot cake.

Mesquite grilling has moved east, and SoHo has discovered the New American Seafood Restaurant.

NEW ORLEANS

New Orleans is an insider's town. You not only have to know whether your kinds of oysters are those at Felix's or Acme--or perhaps the big brownish ones at Visko's or the ones from the private beds saved for the Sonesta Hotel's Desire Oyster Bar--you have to know how they are today. Did the storm last week turn them muddy? Has the supply been low?

Then, if you like your oysters fried, you need a whole new set of facts. Casamento's oysters, raw, are as good as anybody's, but they are better shucked, dipped in corn meal and quickly fried, crunchy and not greasy. But they are served on long slabs of toasted white bread. So maybe the oyster po' boy at the upstairs deli of K-Paul's would be your idea of perfect. The roll is hollowed out, brushed inside with melted butter and heated until slightly crisped. The oysters-- fried in corn meal--are stuffed in, along with globs of homemade mayonnaise flavored with garlic, oyster juice, scallions or beef drippings.

The best dishes in New Orleans have this in common: triple grease. Butter, fried seafood and mayonnaise. Or consider Galatoire's most extraordinary dish, oysters en brochette: oysters wrapped in half-cooked bacon (grease), dipped in egg-milk batter and rolled in flour, then fried (double grease) and ladled with lemon-and-vinegar-sharpened browned butter (triple grease). The trout meuniere amandine, fried to a crisp fluff and ladled with that browned butter is only double grease and second to the oysters.

Locals know that the best time to go to Galatoire's is Sunday afternoon, around 2 o'clock (all the tourists are brunching at Brennan's). And they know not to order the trout marguery, whose white sauce is so thick that the plate could turn upside don and the sauce remain intact. They also know that Galatoire's buys its oysters already shucked, that the boiled redfish with hollandaise is exceptional but that the shrimp clemenceau is served with canned mushrooms and peas.

One learns that New Orleans shrimp are fresh and flavorful, but it is a challenge to find one that is not mushy. Until a few years ago the fiery, rosemary- scented "B-B-Q Shrimp" at Pascal's Manale was one of the great dishes of the United States. Now the shrimp are merely hot and oily, their seasonings pulverized and their savor lost. At Mosca's, the "Italian shrimp" are close to what Manale's used to be: whole garlic cloves in a ruddy and oily sauce. The locals love, even more, Mosca's Italian oysters, which to an outsider taste like Oyster Helper: oysters baked under a thick insulation of garlic-and-herb bread crumbs, soggy and starchy. But insiders spoon it onto Mosca's buttery and garlicky "spaghetti bordelaise."

Not even many insiders, though, know about Barrow's Restaurant and Bar, whose menu consists totally of fried catfish fillets, pale gold, thin-crusted and barely cooked. This is the lightest and crispest and moistest of fried catfish.

What is remarkable in New Orleans is the quality of the frying. Oysters, shrimp and fish are fried lightly, battered barely, and taste fresh, not greasy.

The fad these days is grilled redfish. Frank Zuccarelli, plant manager at Battistella's, the city's largest seafood wholesaler, confirms that redfish has taken over from red snapper, which is too expensive now to be popular. Louisiana, he says, has the largest fish estuary in the world, which makes it the greatest feeding ground there is. There is plenty of speckled trout, weakfish, pompano, catfish, flounder, drum, shark, crawfish. ("You gotta eat crawfish at home," says Zuccarelli. "People don't like to see you suck the heads.") And there is alligator, its meat pale pink to dark beefy red, to be made into soups, sandwiches or alligator sausage.

Redfish remains, nevertheless, the local favorite. A new pub in the French Quarter, Mr. B's, has gumbo--one begins to wonder if it is a legal requirement in New Orleans restaurants--and redfish, grilled over hickory logs.

There are two places and two ways one must taste redfish in New Orleans. One is at Commander's Palace, where it is charred on a wood-burning stove, put on a bed of julienned, crisply saut,eed vegetables and topped with a roux- based but very light and lemony sauce. Commander's Palace is a warren of beautiful rooms, ranging in style from luxurious brothel to treehouse. While you are there, order the Oysters Commander, oysters and artichokes scented with leeks and cayenne. Here sauces have lightened from the traditional roux-heavy ones that Galatoire's has not yet overcome. Commander's Palace is one of the few places it is worthwhile to order fish baked in parchment, in this case pompano in papillotte, and there is the newly fashionable trout with pecans.

Visiting New Orleans without tasting K-Paul's blackened redfish is like going to the zoo and missing the pandas. It is perhaps the most exciting single fish dish invented. An iron skillet is heated to white hot (one is advised not to try this on a home stove). The redfish is dipped in clarified butter, then a spice mixture that is largely cayenne; it is seared on each side for 11/2 minutes, by which time the butter will have burned off, the surface formed a blackened crust and the interior cooked to a white steaminess.

K-Pauls's, now 2 1/2 years old, is considered the foremost Cajun restaurant in New Orleans. The menu changes daily, but if you're in luck it will include batter-fried crawfish-- called Cajun Popcorn--for appetizer or crawfish etouffee in a dark and intricate sauce. Some of the dishes--say, deep- fried mirliton halves stuffed with sausage, shrimp and a hollandaise flavored with oysters and dried spiced meat-- are overwhelmingly rich. But if you have started with a pint- jar full of Cajun martini (gin marinated with hot peppers so that it burns every way possible) you will have an open mind.

Crawfish are in season from around January to June, and during that time the Bon Ton offers a multicourse all- crawfish meal, but one should taste the etouff,ee, smothered with scallions, butter, black pepper, onion and Tabasco, colored coral by the fat of the crayfish. The Bon Ton's crab imperial is also imperative, baked with olive oil, pimento, scallions, mushrooms and white wine, closer to crab Norfolk than to Washington's version of imperial.

For a visitor interested in seafood there is one more vital bit of information to remember: skip Antoine's. Take a look at the grand white-tiled front room. But if you stay for the oysters Rockefeller, which were invented here, you will wonder why they caught on. And you will feel only pity for the good fresh trout or pompano overcooked, perhaps fried in stale-tasting oil and weighted under sauces of depressing heaviness.

MIAMI

In Miami, a northern city vacationing by the beach, seafood is everywhere-- Cuban carryouts, Chinese luncheonettes, waterside crab houses. As in any other big city, Miami's seafood can be good or bad, fresh or frozen, local or imported. Maine lobster is a hot item. The best dish that I found at Mike Gordon's (where people are willing to wait in line, but I don't know why) was a New England-style red snapper chowder. Otherwise, in Mike Gordon's, the national penchant for overcooking seafood and overdosing it with paprika holds true, and the stone crabs are no better than one might find in Washington.

More impressive are ethnic restaurants specializing in seafood. At the little Bangkok Cuisine there are fresh squid salad, steamed whole red snapper and mussels steamed with lemon grass. At the kosher- style deli Rascal House, a line forms at 8 a.m. for a thick vinegared slab of pickled lox or lox and eggs with the onions.

But the longest line is for Joe's Stone Crabs. The locals will tell you there is a way around it: a $10 tip for two people, $20 for four. Whatever the routine, at Joe's nearly everybody gets the stone crabs --$14 a portion and stacked up like firewood and far superior to the stringy, bland stone crabs one generally finds. The rest of the fish are more modestly priced and might be ideal --as our whole broiled pompano was last time--or dismal --as our overripe yellowtail was the same evening. Joe's specializes in huge portions of hash brown or cottage-fried potatoes, fried oysters (at least a dozen for only $3.50), and a coleslaw that is vinegared shredded cabbage (fresh sauerkraut) piled into a small mountain and barricaded with slices of tomato, topped with a dollop of mayonnaise and a scoop of pickle relish. Maybe when stone crabs are out of season Joe's could carry on as Joe's Coleslaw.

KEY WEST

>Nobody can tell you about Key West. You just have to be there. But one small warning: if you feel laid back in Key West, wait until you see how laid back the waiters are.

Not just the waiters. Restaurants tell you they are going to be open when they are not, they claim to specialize in seafood when they serve hardly any, and they charge for pretensions they don't carry out. At $30 a person for dinner at the Port of Call, one expects more than a shrug from a waiter when one complains that the fish has gone bad. And when the sauces taste like Cheez-Whiz and ketchup, one expects lower prices.

You will inevitably be drawn to taste conch in Key West, and will discover that conch does not have much taste. It is mildly like clam, and is apt to be tough, even after being pounded in a valiant attempt to tenderize it. That is why it is usually served ground up in soup or fritters. The soup tastes like vegetable soup, and the fritters taste like hush puppies.

You can also get a fresh tuna salad sandwich. If you are lucky, that will mean that it is made with fresh tuna. So it was at the Half Shell Raw Bar, the kind of inexpensive waterfront bar you always imagine will have fresh home-style seafood. This one does. The menu includes marinated kingfish (too much soy sauce), delicious home-smoked bluefish and whatever else is being caught locally. Not great food, but good and cheap and accompanied by several fresh vegetables.

If you are after conch fritters, they may be best at Papa's Place, a Cuban luncheonette that seasons them with green pepper, scallions and plenty of spice.

Once you have tested conch, concentrate on shrimp and stone crabs. A shrimp cocktail in Key West--even at the Port of Call--is what you always keep hoping it will be. At Claire's, a pineapple-decorated restaurant that captures the sea breezes, you may also find rock shrimp, which taste more like lobster than shrimp (and cost an incredibly low $4 for a large bowlful). And the stone crabs were better than any we found in the Keys, in fact better than we found at Joe's Stone Crab in Miami. And at Claire's the service is energetic, though it doesn't really matter; paper table scarves are set with boxes of crayons to keep you busy while everything is cooked to order.

FLORIDA KEYS

The Keys' restaurants are friendly, amusing and set up to serve seafood, but they're not going too far out of their way to make something of it.

The most famous restaurant, Marker 88, was the starkest example of local limitations. Driftwood, dim lighting, candles lining the stairway, Marker 88 is elaborate and expensive--presumptuous. Oysters Rockefeller are $2.25 each. Smoked kingfish--available in local markets for at most 50 cents a portion--cost $3.75 and was dried out. Conch fritters were light and fluffy but served with a dipping sauce that tasted like an inferior brand of soy sauce. In the Keys you should try yellowtail, an extraordinarily good fish. But you won't want to have to fish it out from under canned asparagus, mushy tomatoes and a lake of butter, as at Marker 88. And Florida lobster is distinctly inferior to Maine lobster, but still not deserving of being encased in a half-inch of mozzarella and pasty tomato sauce and perched on very limp spaghetti. If one were to guess at the sauce on Marker 88's conch steak--which was fried in a light eggy batter-- one might consider A1, worcestershire and brown gravy.

But the less famous show more promise. The Green Turtle has pretty good conch fritters, and conch salad that is like a tomatoey seviche. It turns out a respectable broiled seafood platter. But the turtle and conch chowders, which it sells proudly in cans, taste--as one might guess--canned.

The Lorelei has a waterfront porch that is a glorious place to while away a sunny afternoon and is just right with yellowtail meuni,ere, saut,eed in a light egg batter, or a broiled seafood platter that stars fresh shrimp, though reminds you that the Keys are not the place to order oysters. Not a great restaurant, the Lorelei is undeniably pleasant and is clever enough to keep the food simple and not overdo the sauces. It does, however, promise fresh tuna salad but means by that the salad is fresh, not the tuna itself.

But the least pretentious and perhaps the most satisfying is Manny and Isa's, a Spanish restaurant. Here is the best conch chowder we have found, and shrimp de jonghe that is an astonishing concentration of butter and garlic but irresistible. The fish are fresh and they are best served by a light and sweet tomatoey sauce rather than the "green sauce," which is starchy and alarmingly green. Manny and Isa grow their own Key limes, hot peppers and guavas, and understand the necessity for a good cup of strong Cuban coffee.

BOSTON

Boston, the urban and urbane hub of New England, may consume more fresh seafood than any other part of the country. And so far as lobster goes, Boston is a suburb of Maine.

Old-timers in Maine remember when a kid was ashamed to take a lobster sandwich to school because everybody would know he was poor. But now Maine lobster is fashionable, and Boston's seafood is trucked nonstop to Denver within a day and a half.

But in Boston they crave scrod--cod or haddock under three years of age, though the term grows fuzzier as you go west. Cod, says Bob Gill of Boston's Turner Fisheries, is and always has been the most popular fish in the United States, haddock is now number two and every year tastes are changing.

"Five years ago," said Gill, I don't think we sold any mussels; today we are probably selling 50 bushels a day." New England's belon oysters, newly cultivated French imports, are being shipped all over Europe (except to France, which forbids their import).

Fresh fish is becoming much more popular, and its success story parallels the success of Boston's seafood restaurants. Fourteen years ago George Berkowitz and his son Roger turned a small grocery into Legal Sea Foods (named for the Legal trading stamps the grocery used to give away). It now uses 30 tons of fresh seafood a week in its three locations, each of which still combines a seafood market with on-site dining. You pay for your food before you get it, and your food is delivered whenever it is ready rather than when all the food for your table is ready. And all the seafoods except king crab, shrimp and smelts are fresh.

Legal Sea Foods serves, on large scale, perhaps the most consistently excellent fried seafood anywhere, lightly coated in a "secret" batter of cornmeal, flour and egg, and fried in kosher vegetable oil. The chowder, made by the same person for the past six years, is prepared fresh two or three times a day. Portions are aimed toward generosity: 15 ounces of scallops, 14 to 20 oysters per serving.

The Berkowitz family's seafood market began to change into a restaurant in 1968. "All the Japanese were coming over to MIT to study computers," explained Berkowitz. "They bought raw tuna and started eating it raw right there." So Legal Sea Foods put sushi on its menu. And since then his restaurant business has continued to adapt to changing tastes. By 1976, Berkowitz said, people began changing from cod and haddock to everything from squid to shark. And they moved from fried to broiled to baked and now steamed seafood (though Legal's trendy steamed fish with vegetables clearly needs a longer breaking-in period). The trend, he observes, is for simple preparation. And now, "People are going nuts over swordfish," because it was "the forbidden fruit." He has yet to find a market, however, for periwinkles or sea urchins.

The Salty Dog in Quincy Market lets you pick your own whole fish, then fillets it and cooks it to order. Tatsukichi, a Japanese restaurant not only serves sushi but specializes in kushiage, small skewered seafood snacks that are combined with vegetables (or meats or just vegetables), dipped in crumbs and deep fried. Scallops may be twined with bacon, salmon wrapped around cheese, squid interspersed with okra or celery, or shrimp woven with shiso, an aromatic green- black seaweed. Tatsukichi also steams clams with miso or consomm,e, or even with garlic and soy sauce. It marinates seafoods in a sweet vinegar, perhaps dresses them with a sweetened lemony egg sauce. It dips huge oysters into crumbs and fries them, and serves rectangular Osaka sushi as well as the more familiar oval Tokyo style. >Boston also has No- Name and Jimmy's, waterfront seafood restaurants that seem to be famous simply because they are famous. And it has one of this country's restaurant phenomena, Anthony's Pier 4. Heat lamps line the overhang of the restaurant's roof outside to help protect the long lines waiting in the dead of winter to eat seafood that is no more than decently good, but comes with a view of the busy harbor and a parade of crackers and cheese, relishes, popovers, Caesar salad and a good baked potato.

The rapid growth of the frozen fish-stick business in the 1950s helped to destroy the Boston pier, which had been the biggest fish pier in the world, said Ken Coons, executive director of the New England Fisheries Development Foundation. The trend toward fresh fish is reviving it with the help of a $12 million rehabilitation budget administered by Massport. With the 200-mile fishing limit there is now more fish available, and with the change in Americans' dietary preferences, there is more incentive to go after it. And so Boston, one of the oldest and grandest of seafood ports is becoming one of the newest and grandest sources of fresh fish.

America has survived the fish stick.