WASHINGTON'S Maine Avenue wharf is a haven of hurly-burly after the slickness of Federal City's more sedate shopping centers. In the good old days the fishboats were fishing boats, whose crews worked the water for a week or so and then sailed their catch up the river from the fishing grounds in the lower reaches of the Potomac and in Chesapeake Bay. It was quite colorful and absolutely authentic, and customers could count on the fish being cloudy-eyed and soft if not spoiled, the crabs moribund if not actually reeking, and the oysters dehydrated if not dead.

That's all behind us now, although the aroma lingers on, mainly because the dock stands in a noisome tidal eddy that doesn't flush away the fish and crabs that slop overboard from time to time. The stink is superficial, though; frosty walk-in coolers and glaciers of ice keep the fish and shellfish fresh. Some years ago the city nearly closed the docks down, but the public outcry led to a better solution: The city fixed up the wharf and the boatmen cleaned up their act.

Tourists find the area a quaint contrast to our avenues of pomp and corridors of power, but this is one part of Washington that doesn't cater to them. The docks depend upon the custom of those who come because you can get a nice piece of fish there. Or squid, or conch, or giant freshwater shrimp from Pakistan or huge frog legs from Bangladesh. . . .

There are eight to a dozen boats doing business at a given time, and the competition is mock-fierce. Countermen cry out to passersby from behind great mounds of gleaming fish and bushels of crabs, clams and oysters, and he who hesitates is cost. Entering from Maine Avenue, as most do, the first boat you come to isPruitt Seafood.

"We've been here since well before World War II," says Pruitt salesman S.M. Mister. "I think we're the oldest ones here, and I know we're the best." Mister hails from Melfa, and even 25 years in the Army haven't worn away the soft sweet accents of Virginia's Eastern Shore. He ran his fingers through a pile of iced shrimp, poking and prodding for soft ones. "We rotate our stock fast, and anything that isn't perfect goes straight into the dumpster. Just one bad shrimp can spoil a 50- pound box, so we just can't afford to fool around. Disappoint people and they don't come back, and repeat business is what we depend on."

Half a dozen men can man the counter on weekdays, but it takes two or three times that many to keep up with things on weekends. "The big day used to be Saturday, now it's Sunday," Mister said. "Asians particularly come on Sunday, I don't know why. Maybe they're working all the rest of the week, but Sunday's when we see 'em. During the Redskin games they pretty much have the place o themselves."

It takes stamina and energy to work the fishline, Mister says, but mainly it takes patience. "A lot of customers, they'll go through every fish in a display you've just finished arranging, and then maybe they buy one or maybe they don't. Then, just as soon as you get finished putting the display all nice again, here comes somebody else tearing through it. So you just put it back again, because a big part of the attraction here is that you can handle the stuff, it isn't behind glass."

Mister lines up firmly on the Chincoteague side in the great oyster argument. But while he asserts that there's more to it than just the saltiness of the Chincoteagues, he won't venture to speculate about what makes them so much better than your Bayside oysters, or your Blue Pernts from Long Island or your transplanted belons (or for that matter, your belons in their native France). He just shucks a couple and lets you make your own comparison. (There isn't any.)

Custis & Brown also has been there since before World War II, and the manager says business has never been better, mainly because of the influx of Third World immigrants who prefer the open-air style of market.

But there's bad news lurking behind the apparent abundance: Most of the fish is trucked in from North Carolina now. Shipments from Chesapeake Bay have been declining steadily for a decade, and fell off sharply this past summer. The plight of the world's largest and once most productive estuary is Topic A on the docks because virtually all the men and women on the fishboats come from families that "work the water," and most still make their homes on the Eastern Shore.

So strong are the ties to the Bay region that the typical Maine Avenue boatman works seven days straight, often from well before dawn to long after dark, so that he can spend alternate weeks down home. Many never leave the dock during the week, eating and sleeping aboard the boats.

The Jessie Taylor family, which comes from Smith Island, smack in the middle of Chesapeake Bay, established its pierhead on Maine Avenue just after the war, and just recently installed its second boat, or barge. It has counter space for the weekend rush but mainly serves as a dormitory, giving the Taylor crews far more space and privacy than most of their rivals. Most of the crewmembers are Smith Islanders also, and they're almost like members of one big family, except that they seem to get along together better. The weekly shift changes on Tuesday morning, with brother handing off to brother and cousin swapping car with cousin.

Jimmy Byus worked the fishboats for many years, but all the time was thinking that "There must be something for me to do besides work for another man." Four years ago he made his move, buying the fishboat Louise Travers and, more important, the long-term contract that entitled him to precious dock space. The next thing he did was scrub her down good, so that you'd never know she'd ever had a fish aboard, and fill her up with vegetables and fruit.

"It wasn't much point in just running another fishboat," the Baltimore native said. "People come down here, they get some fish or whatever for dinner, but then they need their greens and things to go with it, and here I am." They can also get their okra, four kinds of onions, crown figs from Greece, jalapeno peppers, prickly-pear cactus fruits, persimmons, fava beans and no end of other exotica, including leatherskinned muscadine grapes, whose lingering musky flavor can start tears from a displaced Southerner.

Byus donated the Louise Travers to the Solomons Museum, where she'll be restored and returned to her original duty as an excursion boat. She was towed away a few weeks ago and Byus says he doesn't miss her, because his new barge Cara Jayis a whole lot handier to work from, "but I'm going to have to sell a lot of tomaters and potaters topay for her." Instead of using the shift system, Byus just opens on Thursday and tries "to sell it all out by Sunday evening."

Capt. Whites Seafood City, founded by the late Bronzie "Pete" White of Hallwood, Virginia, led the switch from boats to barges about five years ago. "It's just a whole lot better system," said his daughter, Patricia White. "You've got room for walk-in coolers and icemakers and everything."

She shares supervision of the operation with Billy and Sonny White, and is utterly unfazed by the fact that she's one of the few women holding a position of authority in what must be one of the principal bastions of male chauvinism in the Western Hemisphere. After years of working in a chicken-packing plant, it's a piece of cake, she said.

One problem that has always plagued the Maine Avenue fishmongers is that one fishboat looks pretty much like another, and all offer much the same merchandise. Capt. White's got a little bulge on the competition a while back by installing a public-address system over which a barker kept up an enticing -- and usually endearing -- banter. But then a boat across the way came back with its own system, which played music so loud nobody could hear anything, and a truce was negotiated. Once again the only cries that are heard on the wharf issue unamplified from human throats.

The Wayne Christy is the last full-time working fishboat on the dock, although there are a couple more that are mainly used to maintain docking rights but may be pressed into service on peak weekends. Jerome Jackson took her over from now barge-borne Custis & Brown a couple of years ago, and a look at her cramped and sloping deck is a reminder of how much more sense the barges make, even though they ain't quaint. Asked why they were still working from an actual boat, a crewman said: "Because we don't have enough money for a barge."

The next stop after buying a fish is usually the Virgo Fish House, open 365 days a year to clean your fish at 25 to 50 cents per pound, 50-cent minimum. If you're looking for a chat or just trying to pass the time of day, Benjamin Edwards is not your man. His concentration on the task at hand is awesome, as is his production rate. The other day, without seeming at all hurried, he scaled, gutted, split and wrapped a couple of three- pound sea trout in 30 seconds, and cleaned nine Norfolk spot in less than two minutes.

Edwards maintains an absolute deadpan, even during such exchanges as this: Fellow worker: "Rudy workin today?" Edwards: "Naw, man, Rudy ain't workin." Fellow worker: "Then how come he sweatin?"