The Katama Bay oyster is the talk of Island raw bars. Lovers of seafood now have a local oyster available through most of the year. This Island oyster is making its way across the eastern seaboard to Washington, D.C., New York and Boston.

This is not your usual native wild oyster growing on the silty muck and sand of the Island's coastal ponds. This bivalve never touches bottom, residing instead on plastic trays. Its entire adult life is spent in the care of Island commercial fishermen.

This oyster is a product of the emerging science of aquaculture, and this way of farming the ocean is growing on the Island. Last year, one grower shipped 20,000 oysters to market, and this year he is shipping many times that. In a short time, the Island will be shipping millions of oysters to the mainland each year. While right now there is the Katama Bay oyster, expectations are high that in the years ahead there may also be oyster cultivation projects in Lagoon Pond and Menemsha Pond. These oysters can reside wherever local ingenuity and Mother Nature allow them to grow.

On Wednesday morning, three of the Island's shellfishermen were out on Katama Bay, tending their oysters from their inconspicuous floating platforms. These are shellfish nurseries; like icebergs, these floating vessels offer a lot more under water than can be seen on top. Each platform is a floating hotel, filled with oysters.

Tom E. Berry, 52, of Edgartown, is one of the successful fishermen. He was formerly a commercial fisherman working out of Chatham. In the 1970s and 1980s he worked on fishing boats on Georges Bank, pursuing cod. "When the fishing dried up I went back into the food business," he said. He moved to the Vineyard in 1993. In 1995 he was one of 16 commercial fishermen who enrolled in a National Marine Fisheries Service program to help fishermen explore another way to make a living, by raising shellfish. Rick Karney, director of the Martha's Vineyard Shellfish Group, was their instructor. At the time, they were instructed on how to raise bay scallops, quahaugs and oysters. Many of them had to invent their own techniques for raising shellfish.

Six years of experimenting later, at least four commercial fishermen are invested in the new technology and starting to see income from it. Last year the money started coming in. The fishermen found that consumers liked what they were growing and markets were willing to pay from 50 to 60 cents a piece.

Last winter was the defining moment. Mr. Berry and Jack Blake entered their oysters in the Old Ebbitt Grill's annual Oyster Riot. They learned their oyster was not only liked, but one of the restaurant's most asked-for oysters.

They learned that consumers were willing to pay $20 for just a dozen of their shellfish.

Mr. Berry said a number of factors contribute to the flavorful success. "The oysters feed on a sweet plankton, and they are always in saltwater." That sweet and salty flavor and a high meat to shell ratio make the shellfish attractive.

There is a lot more meat to a shellfish from Katama Bay than a Nova Scotia oyster.

Out in the environment, a natural setting oyster takes up to four years to reach the harvestable size of three inches. With this new technology, Mr. Berry said, they can cut that growing period in half. A key ingredient to helping an oyster grow involves availability of food. The fishermen devised a floating platform, a device they call a tidal upweller, which allows the tidal currents to send a continous stream of fresh, algae-rich seawater over the oysters. Katama Bay has all the right algae growing in it. Unlike oysters residing on the bottom, these bivalves are continously fed every time there is a change in tide.

In coastal ponds like Edgartown Great Pond and Tisbury Great Pond, there is not that much water movement.

These oyster-growing fishermen treat their product a lot differently than nature. For one thing, they clean their oysters with high-pressure water. Mr. Blake also takes his oysters and runs them in a spinning metal basket. This combination of techniques removes barnacles from the oysters and causes the oysters to grow a deeper shell than their wild cousins.

Mr. Blake incorporates another low-tech method for removing creatures from the oyster shell: He drops the oysters in a high concentration of brine for 15 minutes.

The end result is a good-looking oyster that displays especially well on ice in a shellfish raw bar.

Raising oysters is good for the environment and for the natural set of oysters that already reside in Katama Bay. Mr. Berry said that throughout this summer, he and others culled their oysters to a manageable crop and ended up giving thousands upon thousands of oysters to the town shellfish constable for distribution in town waters.

"I would guess that perhaps in 10 years we will have established a wild oyster fishery here in the Narrows, the harbor and in the bay," Mr. Berry said.

Healthy oysters are great for improving water quality in a pond, for they feed on algae and algae feed on nutrients. Mr. Berry said: "In one year, 100,000 oysters will bind the same amount of nitrogen that 27 adults create." That translates to the amount of nitrogen created by those living in nine homes with three bedrooms each. So one million oysters would counteract the impact of 90 homes on the environment, he said.

In the early stages of developing their industry, the fishermen looked at a number of different shellfish to raise. Mr. Berry said the fishermen chose oysters for many reasons. The first reason is that oysters get a high price on the market. "Bay scallops are difficult to raise because they swim and don't like to touch each other. Quahaugs are already being produced at great numbers in other parts of the country." So they focused on the high end, the most lucrative bivalve.

Other growers include Scott Castro and Roy Scheffer.

Credit for the success of the Katama Bay oyster can be shared by a number of organizations. Last spring the Seafarers Friends gave $8,000 to the program, and each of the fishermen received $2,000 to purchase needed equipment. Most of the technical and financial help has come through the Martha's Vineyard Shellfish Group. Mr. Karney said yesterday: "I look at them as my students. I have a lot of pride in the fact that they having some success."

Promoting the product is another area where the fishermen have received support. This summer and last, Capt. Bob Blanchard of Edgartown Marine Supply ran Edgartown harbor and aquacultural tours. He took hundreds of interested visitors out to meet the fishermen and see their floating rigs.

There is an old bit of advice that has been passed from one generation to the next: Never eat a locally caught oyster in a month that doesn't have an "r" in it. And for years, consumers preferred oysters imported from Canada.

This is part of the change. Cultured oysters can safely be eaten all the year around.

Louis S. Larsen Jr. of the Net Result, a fish market in Vineyard Haven, is among the early buyers. Mr. Larsen said consumers now ask for this oyster by name. "I had them all summer long. I probably sell three oysters from them to every one I get from afar."