SURELY historians would love to have interviewed the first person who ever ate an oyster. The bravery, the courage, the imagination of that hungry soul are never to be known. Nor the persuasiveness it took to convince the second eater.

The softshell crayfish, though, is a subject of gastrohistory that is being documented at this very moment.

And like the ancients who lived diminished lives without oysters, even now scoffers refuse to believe in them. "Softshell crabs, you mean." No, crayfish. "Aw, c'mon."

Yes, softshell crayfish, just like their crab cousins, having shed their shells and ready to be eaten whole. No more peeling away a pound of shells for a scanty portion of single-bite meat. An entire briny, claw-to-tail crunchy sweet crustacean, one that nobody ever thought of eating before.

Even Moe Cheramie of McLean's Old New Orleans Seafood Market, who grew up on crayfish in Louisiana and studied the creatures at Louisiana State University, says, "It didn't even dawn on me that they existed."

It turns out that crayfish--which were once considered a pest in Louisiana rice fields and are now being cultivated in those same fields, with the rice grown strictly to feed the crayfish--molt 12 to 20 times a year. Nobody yet knows how long their shells remain soft but it might be as long as a couple of days, and it seems as if they stay soft once they are out of the water.

It also turns out that after eight years of fiddling with possibilities and a couple of years having actually dredged some from the mud where they hide to protect their vulnerable soft bodies, Harlon Pearce is finally marketing this new delicacy. Pearce, a seafood wholesaler in Metairie, a suburb of New Orleans, first saw softshells being used as bait in Wisconsin; his partner-in-fishing Ronnie Dean found a few in a drained catfish pond, tried 'em and liked 'em. So they joined forces with Dean Cain, who had been studying crayfish at LSU, and set out to devise a method of harvesting them.

Thus far their method is exclusive and unpatented, but they figure others are trying to harvest softshells and may be coming close, so they are playing it close to the chest. "Nobody's ever seen 'em," Pearce said about his home-rigged fishing boats, adding that television stations and journalists have been badgering him so much that "we've got 'em lined up."

But as Dean put it, "We've dropped a hundred grand into this thing just to get where we are now." And they aren't about to give away any expensive secrets.

The early morning chill still lingered around the Holiday Inn coffee shop west of Baton Rouge as the first outside observers waited to be driven to what these three partners consider the world's only softshell crayfish dredging operation. Pearce, Dean and Cain insisted there be firm ground rules for the visitors, but weren't too sure what those ground rules should be--whether or not the boats could be photographed and from what angle, whether Dean's or Cain's names should be mentioned since it was Pearce who handles the commerce. Anyway, noted Cain, the fishing method had evolved since last year, and next year it may be totally different.

What the problem boils down to--that is, once the crayfish are caught--is control of the market. "We want to always have a little bit more market than we have supply," explained Pearce, who talks as fast as a motorboat at full throttle. He wants to "keep the customers hungry," to "keep the mystique," prevent the customers from getting "too picky." Thus last year, the first time he marketed the crayfish, he sold to only four or five restaurants in New Orleans. Just two weeks ago he started shipping the crayfish, 200 pounds of them so far, to the Washington area, where they have been tried out at New Orleans Seafood Market, U. S. Fish, and restaurants 219, Nora, La Mare'e, Maison Blanche and Chaucer's.

"I don't know exactly where he's getting them," said Cheramie, who has been distributing the crayfish in Washington.

The secret is not really where he is getting them, but how. The first visitors were driven, in broad daylight, down a back road to a series of rice paddies cum crayfish ponds, where a farmer in a red cap and down jacket discarded his taciturnity just long enough to mutter, "Be careful walkin' in the grass." Water moccasins.

Two silent fishermen were chugging their boat from trap to trap pulling in hardshell crayfish. And on the shore was a flat-bottomed aluminum paddlewheel contraption that looked as if Rube Goldberg hadn't been able to keep his hands idle during a boat ride. Actually, it could have passed more believably as a piece of farm equipment than a boat. Although Pearce said each of their three boats cost $15,000, to an untutored eye they were merely rigs of bike chains, rakes and bathroom pipes. "It don't look like much but it costs a lot," said Dean.

"There is some equipment we don't want shown," Dean warned a photographer. One wondered whether it was as much embarrassment as secrecy.

Pearce and his group are now fishing 70 to 90 acres for softshells, the same ponds that are being fished for hardshells; and even with their contraptions they catch three times as many hardshells (which the farmer gets in return for letting them harvest his pond) as soft. But Pearce sells those softshells for about $8.50 to $9.50 a pound, whereas the hardshells only bring 30 to 50 cents a pound wholesale.

The reason nobody's much noticed softshells before, or fished for them, is that they are hard to find in the mud, and they don't go after bait in traps, apparently being wary that hardshell crayfish might eat them. Pearce's group simply adapted the notorious electric-charge method of fishing; in this case the boat transmits intermittent electrical charges to the water. The charge is small, like static electricity, Pearce was quick to specify; "You're not pounding them with that charge, you're just tickling them." But the observers could see it was enough to pop some of the crayfish clear out of the water.

The ponds are only 1 1/2 to 2 feet deep. When the crayfish are dislodged from their lairs by the charges the current drives them into a trawl, where a chain-driven rake pulls them into a tray so the fisherman can separate the soft from hardshells and store them on ice in coolers. Thus the boat must be designed to leave the fisherman's hands free for sorting. As long as crayfish season lasts--late November through June in Pearce's area--he expects softshells to be available, but he's not really sure about their season yet. Next year he'd like to own his own land rather than sharecropping, so he could try to extend the season. He'd also like to build a boat that doesn't need to be moved from one pond to another--an all-day job that winds up tearing up the boat--but could walk a pond like a combine and move itself across the levees.

Some farmers have worried whether the electrical charge might sterilize the crayfish left in the pond, Pearce said, but his past experience has shown no such problem. One could, he supposed, harvest softshells by keeping hardshells in tanks until they molted, but he's been too busy pursuing the electrical method to experiment. He's also used nets, but found them inefficient.

His harvesting method can only be done in cultivated ponds, he explained, because it requires a pond with an even bottom and water devoid of other fish, algae and sticks. But that's not the only reason for using cultivated ponds. Fishing with electric current is illegal in Louisiana, except in private ponds. And even then it is illegal to transport electric fish shocking devices on public roads or highways.

Once the crayfish are harvested they keep better than hardshells, said Pearce, if they are kept very cold. He has found that they can be held three to four days; Washington buyers have complained that the crayfish were not live when they arrived, but Pearce claims that they need not be live to be good.

The sizes vary greatly. Some are larger than hardshells are likely to be, because the mesh of the hardshells' traps limits the size of those caught. But some are very small, a problem that could be overcome by increasing the distance between the trawl's metal bars so the smaller ones are sifted out. Pearce claims some people like them small.

Washington chefs' first experiments have yielded a mixed response. The French chefs who tried them have not much liked them. Maison Blanche rejected them because they were too mushy. Jean Bosch at La Mare'e also found them mushy and decided that softshell crabs have more flavor; he had saute'ed them the first time, but would try them again in a bisque. Nora Pouillon at restaurant Nora was very disappointed with her crayfish, which she found dirty, crushed, half dead and half hardshell; but one of her cooks, Debbie Trost, thought them interesting to deal with, and said the soft ones tasted wonderful. They wasted a lot of the meat, since they thought it necessary to cut off the heads. At Chaucer's, too, Jeffrey Bleaken used just the tails, having dusted them with flour and deep-fried them, then served them with a spicy tomato sauce over pasta. Only one customer at Chaucer's ordered them, but the staff ate them happily.

Actually, all that needs to be cut off the softshells is the tiny triangle that encompasses the eyes, the mouth and a small calcium deposit, much as one cleans softshell crabs. And while the hardness of the shells varies, once they are deep-fried, which is the way they are most often cooked in Louisiana, they are crisp and likely to lose their toughness, said Pearce.

Cheramie, being from Louisiana, soaked them in milk seasoned with mustard and dipped them in seasoned crumbs, then fried them for three minutes or so. What he liked about the softshells was that they go a long way; a pound serves four rather than one or two people as hardshells do. Ronnie Dean seasons the softshells heavily with cayenne and black pepper, "in South Louisiana-type way," dips them in cornmeal and flour and fries them until they float, plus a few moments to crisp them.

In Alexandria's 219 restaurant, which serves New Orleans-style food, the softshells were a sellout dipped in milk and cornmeal, deep fried, then topped with saute'ed lump crab meat and bearnaise. The tiny ones went into a bisque. K-Paul's restaurant in New Orleans has not only stuffed and fried them, but also smoked them lightly, dipped them in batter and fried them. Patout's in New Iberia has stuffed them with the traditional Louisiana bienville stuffing, fried them and topped them with a bienville sauce. Alex Patout, the proprietor, also likes them just plain deep-fried, and finds them delicious, particularly because they have stored up extra fat for their molting period, and the fat is "the dominating force in crayfish." Pearce says the large ones are better for saute'eing, the small ones for frying.

Since they are new and unknown, as Cheramie put it, "You gotta sell them." Steve Himelfarb of U.S. Fish said they are not in his "top ten" favorites among seafoods, but they are "cute," and he managed to sell a hundred pounds the first day he had them. But he added the disclaimer, "I can sell anybody anything one time."

Harlon Pearce, too, knows how to sell something nobody's ever even heard of before; he is the kind of guy who could probably talk you into trying your first oyster. But he sees the market ready to expand. "The crayfish is a sleeping giant industry," he predicts, and you know that he is setting the alarm clock.