Faced with the most dismal oyster catch on record, Maryland has opened five areas of the Chesapeake Bay to dredging by watermen's power boats.
Natural resources officials say they authorized the change in an emergency regulation last Friday at the urging of watermen and legislators, who argue that it will increase this year's harvest and rehabilitate oyster bars that are smothered in silt.
Scientists and conservation officials reply that increasing pressure on oysters will not halt the shellfish population decline and could make things worse.
"Power dredging has been severely restricted for more than 120 years because it is so much more efficient [than traditional tonging]," said Roger Newell, an oyster scientist at the University of Maryland's Horn Point laboratory.
"Now we're down to historic lows, and we're changing the rules to harvest more oysters. It's exactly the wrong way to go."
Eric Schwaab, the Department of Natural Resources fisheries director, said the agency would not have acceded to the winter power dredging "if we thought there was a big downside."
He expressed frustration that "for all our years of oyster restoration programs, and a lot of successes, we're obviously not moving in the right direction."
"It's almost a case where we might as well pull out all the stops," he said. "We don't see that we have a lot to lose."
As to whether power dredging will help the oyster habitat, he said, "We don't know how much upside there'll be, other than to help out watermen."
No one will know until the commercial oyster season ends March 31 how many shellfish the power dredging will produce, but it could add up to 10,000 bushels to a projected harvest of 40,000 to 50,000 bushels, Schwaab said.
As recently as 1999, watermen harvested 423,000 bushels of oysters. But two drought years have made the bay saltier, aiding the spread of two parasitic shellfish diseases, MSX and dermo, which have decimated the oyster population and watermen's already sparse winter incomes.
Legislators from the oystering counties of the Eastern Shore and Southern Maryland, encouraged by a pledge from Gov. Robert L. Ehrlich Jr. to help watermen, are working on bills to further expand and make permanent the power dredging, according to DNR officials.
Sen. J. Lowell Stoltzfus and Del. Kenneth D. Schisler, Republicans representing the Mid- and Lower Shore, have made improving the oyster habitat a priority. To that end, they say, expanded power dredging brings buried shells to the surface, creating the hard, clean surfaces ideal for baby oysters to settle on and grow.
"It's going to help reproduction by getting the silt off the oyster beds," Schisler said.
But scientists, including Horn Point's Newell, who has documented the way healthy oyster populations filter enormous quantities of pollutants from the bay, are not convinced.
"This type of bottom rehabilitation actually is the most effective way to restore oysters," he said, "but it's not accomplished by using traditional power-dredging techniques."
Ben Parks, a waterman from Dorchester County, noted that DNR has hired many oystermen there in recent years to dredge up buried oyster shells after the commercial season is over. Cleaned of silt, the shells are piled up to create new habitat in state restoration areas.
"There's not enough money to do much of that, so we thought, if we can get a few bushels of oysters a day power dredging this winter, we can afford to keep cleaning up the bottom in the process," Parks said.
Greg Price, an oystermen out of Chance, Somerset County, has been power dredging for the past four years in a very limited area approved by DNR north of Smith Island. He said he is "absolutely convinced we have improved the bottom there."
Before his power dredging started, he said, his catch was five to six bushels a day. Now it's six to 10 bushels.
"The real change," he said, "is this year we can see a whole lot of spat [baby oysters] on the shells we've been dredging up." Dragging the bottom, he argued, has kept the oyster bars cleaned of silt and primed for the attachment of new oysters.
But scientists say the same salty conditions that allow disease to spread also encourage the production of spat. They say there is no research proving that this kind of winter power dredging improves the oyster habitat -- and some strong evidence that it does not.
Underwater videos commissioned by DNR to evaluate oyster restoration techniques show that shells, once exposed, become covered with silt again, often within a few weeks. The way to generate clean shell for spat settlement would be to expose it around spawning time, in July and August - not in winter, scientists say.
Even in studies of oyster bottoms turned up by dredges in the summertime, "we see no strong indication this vastly improves spat sets," said Chris Judy, chief of DNR's oyster programs.
Also, DNR's videos show that even after several days of power dredging, much of the bottom in the area is unaffected.
The reason is that dredges towed by typical oyster boats operate in a haphazard fashion and are not very efficient at digging up shell, according to Gary Smith, a scientist at the federal-state Oxford Marine Laboratory.
Smith, who has surveyed the habitat on thousands of acres of bay oyster bars with sonar and video, says the watermen do have the correct concept.
"We estimate more than 95 percent of all historic oyster habitat [once covering 200,000 acres] is buried under sediment," he said.
But he said effective dredging usually requires special equipment designed for the task.
There might be "some places out there where traditional watermen's power dredging could help, but no one can say where that is without actually studying the bottom," he said.
Other skeptics of the expanded power dredging include Bill Goldsborough, the Chesapeake Bay Foundation's senior fisheries scientist.
Goldsborough said the environmental group agreed to limited power dredging a few years ago after assurances that four oyster sanctuaries - where the bottom is off-limits - would be created to offset the effects of increased harvests.
He said videos of the bottom on three of those sanctuaries show it to be "worthless" oyster habitat -"shifting sand mostly."
"I'm really disappointed in the whole process," he said.
DNR has also heard concerns from the Maryland chapter of the Coastal Conservation Association, a sportfishing conservation group.
"The big selling point of this power dredging was it would help the oysters while helping the watermen, and we haven't been able to find any information that this is scientifically justifiable," said Sherm Baynard, a CCA spokesman.
Staff writer Mike Dresser contributed to this article.