To praise from environmentalists and complaints from watermen, Gov. Martin O'Malley outlined plans Thursday to restore the Chesapeake Bay's depleted oysters by prohibiting commercial harvests in large portions of the bay while leasing other areas for aquaculture.

Declaring that Maryland's long-standing approach to managing the bay's oysters no longer makes sense, O'Malley called for a major expansion of the current patchwork of sanctuaries, where oysters may not be removed. And he offered to help watermen move into aquaculture.

"We can do better - we need to do better," he said in outlining his plan at the Annapolis Maritime Museum, a former oyster packing house flanked by a marina. "Our economy needs this shot in the arm; our watermen need this shot in the arm." But Jim Mullin, executive director of the 250-member Maryland Oystermen Association, called it "a sad day" because limiting harvest areas would hurt watermen who are already struggling to pay bills on diminished catches: "They're going to take a culture and heritage and push it under the rug."

Under the plan, a few rivers would be completely off-limits to oyster harvesting - the Magothy in Anne Arundel County, and the Little Choptank on the Eastern Shore - plus major stretches of the Chester, Choptank, Patuxent and St. Mary's rivers. Also set aside would be sections of the main bay between the Patapsco and Back rivers, and between Hoopers and Smith islands.

State officials also propose to make 600,000 acres of the bay available for leasing to individuals or businesses that want to raise oysters, including more than 95,000 acres that had until recently been off limits to aquaculture.

The bay's oyster population has dwindled to about 1 percent of historic levels, as overfishing, habitat loss and disease have taken their toll. Watermen have landed only about 100,000 bushels annually in recent years, a far cry from harvests of 2 million bushels or more in the 1980s. State officials say only about 200 watermen actively oyster now, as a pair of chronic, parasitic diseases continue to kill off oysters before they can grow to market size.

Besides their value as seafood, oysters have had another important - though diminishing - role. They filter silt and other pollutants from water, and provide habitat for fish and other aquatic creatures. But of 270,000 acres of bay bottom that once featured thriving oyster bars, only about 36,000 acres are left, state officials say, the rest silted over and virtually barren. The proposed sanctuaries would extend protection from about 9 percent of the remaining viable oyster habitat to 24 percent.

Meanwhile, by opening more areas to oyster farming, O'Malley hopes to spark growth in Maryland's nascent industry, which lags behind Virginia's.

In outlining the plan, O'Malley stressed aquaculture's economic potential. Within five years, private oyster farming could be a $25 million-a-year industry, employing more than 200 people, said Douglas Lipton, a University of Maryland economist.

"Certainly these waters have supported a lot of families for a lot of years," the governor said. "And we want to make sure that we do what we must in our own bay so that the bay can support jobs and livelihoods for years to come."

The state still plans to allow oyster harvesting in waters not set aside for sanctuaries or private aquaculture. About 168,000 acres of natural oyster bars would be retained for watermen, officials say, including roughly three-quarters of the areas where oysters still thrive.

Scientists and environmentalists have long urged the state to create more protected areas, so oysters have a chance to grow larger and acquire a natural resistance to the diseases plaguing them. They praised the governor's initiative, calling it a "new paradigm" in the state's approach to managing oysters.

"It's been a long time coming," said Kim Coble, Maryland director of the Chesapeake Bay Foundation. The state is "finally and truly recognizing the ecological value of oysters."

Larry Simns, president of the Maryland Watermen's Association, called the state's proposal a "disaster," saying that it would force many watermen to quit oystering without giving them a real chance to switch over to oyster farming.

The state's plan to close the Chester River, Simns said, would pose a severe handicap for watermen there who still catch oysters the traditional way: by hand with long wooden tongs. He said watermen might be willing to try farming oysters, but often lack the money to go into business - buying "seed" oysters from hatcheries and then waiting up to three years for them to grow big enough to be sold for income.

"They're forcing us out of one business and not ready to start on the other one," Simns said.

Natural Resources Secretary John R. Griffin said his department would pay watermen to help rehabilitate silted-over oyster bars in the sanctuary areas, and also would offer grants to watermen to help them buy the equipment needed to get into aquaculture. The DNR has about $2.5 million in federal and state funds set aside to help watermen make the transition, said Tom O'Connell, state fisheries director.

Griffin said officials would hold public forums on the plan over the next few months and could tweak it before proposing regulations in the spring. But he stressed that the administration is committed to expanding sanctuaries and promoting aquaculture, despite the watermen's opposition.

Among those in the crowd for the governor's announcement were a few entrepreneurs hoping to lease bay bottom so they could start or expand oyster farms.

Jay Robinson, who runs a seafood company in Dorchester County, and accountant Ryan Burgey of Berlin hope to lease up to 1,000 acres of bay bottom. They plan to plant hundreds of millions of oysters and employ 25 to 30 people tending them.

"We need to get our name on a piece" of bay bottom, said Bergey, before they can get financing to start the business.

Also there, listening with mixed feelings, was 62-year-old Ben Parks, a lifelong waterman from Dorchester County.

"I don't know what my grandkids and son might do, but you've got to keep an open mind," said Parks, who crabs, oysters, fishes and runs fishing charters to make a living.

But given the seemingly inexorable decline of the traditional wild oyster fishery, he said a shift was "inevitable."

"It'll always be watermen, but I think they're going to have to look at the way they do business, and change," Parks said.

An earlier version misstated the extent of one of the sanctuaries. The lower portion of the Chester River would still be open to commercial harvest. The Sun regrets the error.