New hope for restoration of oyster

ON THE BAY

Ariakensis: Introducing a non-native species could produce a sea change - for good or ill. Few are certain.

April 06, 2001|By Tom Horton | Tom Horton,SUN STAFF

IS IT TIME to throw in the towel on the bay as we have always known it, to consider importing a new and (maybe) improved ecosystem to help the troubled estuary recover?

Such decisions seem possible after an informal meeting of a few dozen watermen, scientists and environmental managers last week in Annapolis.

They gathered to see a creature named Crassostrea ariakensis, the Suminoe oyster, native to China, Japan, India, Pakistan and other coastal nations of Southeast Asia.

Virginia has been experimenting since 1996 with ariakensis, a cousin to our bay's native Crassostrea virginica.

Ariakensis looks like our oyster, tastes as good, grows a lot faster and is highly resistant to the MSX and Dermo diseases that continue to depress the bay's shellfish to near-historic lows.

"It looked pretty phenomenal, to be honest," says Bill Goldsborough, chief fisheries scientist for the Chesapeake Bay Foundation, which has always been against introducing "exotic," or non-native, species to the bay.

But the new oyster on the block presents a tempting prospect.

Oysters have finally gained recognition as being more valuable to the bay than just as tasty, profitable hors d'oeuvres. They also provide, in the myriad nooks and crannies of the reefs or "rocks" they form, a protective habitat for blue crabs, juvenile fish, their own young - more than 300 different kind of organisms in all. Larger species feed on the reefs, making oyster rocks prime fishing grounds.

Most important, it has been calculated that oysters, as they pumped water through their gills to feed, once filtered and cleansed a volume of water equal to the whole bay every few days.

Today's oysters, their numbers severely depleted, take more than a year to do the same work of clarifying the bay's algae-clogged waters.

Oyster restoration has become a key strategy of the bay cleanup by Maryland, Virginia, Pennsylvania and the federal government. Increasing oysters tenfold by 2010 is the ambitious goal.

But, with the seemingly intractable disease problems, achieving the cleansing filtration of centuries past could at best take many decades and cost many tens of millions of dollars, says Ken Painter, an oyster scientist with the University of Maryland.

"The results we need may be in someone else's lifetime," agrees Jim Wesson, who heads Virginia's oyster restoration program.

No one, including watermen who came last week to see and taste the new oyster, advocates a bombs-away introduction of ariakensis to the bay.

The evidence is that such an introduction would be irreversible, that the virginica oyster that co-evolved with the bay's other creatures over thousands of years would be overrun. (Virginica and ariakensis don't interbreed.) Also, there's ample history to caution against new species introductions - from marsh-chomping nutria to underwater grass-eating mute swans, from zebra mussels threatening Great Lakes food webs to the MSX disease that came from putting another Asian oyster variety in the bay decades ago.

That oyster, Crassostrea gigas, didn't survive here, but the disease it brought can't be eradicated.

"I hate to say it, but we're not going to beat these damn oyster diseases, and we're not going to beat this cloudy bay water. We see it getting worse and worse every year," says Larry Simns, head of the Maryland Watermen's Association.

"So we're looking at everything to help us from going down the tubes - crab hatcheries, maybe some kind of underwater grass that can survive polluted waters, and these new oysters. I hate to say it, but it tastes just as good as our own oysters," Simns says.

What watermen, environmentalists and state fisheries experts in Maryland seem to agree on is that we should begin careful experiments to evaluate ariakensis, as Virginia is doing.

Virginia has been using a strain of the oyster it has bred to be sterile (an unequal number of male and female sex chromosomes prevents reproduction).

Introduced species of "exotic" oysters can be highly successful. Crassostrea gigas has become the basis of huge shellfish industries in France and on the U.S. West Coast.

The bay states must proceed with caution, but they must proceed. Regaining large stocks of oysters to filter the water could be a key to jumpstarting the return of underwater grasses and aquatic oxygen levels, both victims of algae-filled waters.

There might be a middle ground, short of letting the new oyster run wild. The technology exists to mass-produce them in sterile versions as the basis of an oyster-farming industry.

This could have social consequences. What would happen to the market for wild, native oysters harvested by watermen?

Other downsides are bound to occur. There are hints that the new oyster's shell might not be thick enough, when young, to withstand blue crab predation, and that it might not form reefs like the native oysters.

But, states including North Carolina are doing evaluations of ariakensis, and Painter says, "There's a real danger, if we stick our heads in the sand, someone else is going to do this anyhow."

Imagine how these oysters could filter the Chesapeake

Talk about filtering the bay: Archaeologists in Peru's Andes have uncovered fossil oysters that lay on the seabed 200 million years ago. Each is 11 feet across and 660 pounds.

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