Oyster bed checks Survival: A biologist and Chesapeake Bay Foundation staff members are trying to save bay oysters from fatal diseases.

July 17, 1996|By Timothy B. Wheeler | Timothy B. Wheeler,SUN STAFF

CROCHERON -- Standing hip deep in murky water, with the bottom mud sucking at his feet, Kennedy Paynter checked the table setting for what he hopes will become a movable feast.

The biologist from the University of Maryland reached into the water and hefted a 30-pound, plastic-mesh sack of oyster shells.

"Nothing yet," he said, peering into the glistening mass of greenish shells, tinted by a thin coating of algae.

With the bay's oyster population ravaged by diseases, Paynter has teamed with the Chesapeake Bay Foundation to try "catching" freshly spawned baby oysters where they are most plentiful and moving them out of harm's way. The parasites that kill oysters -- MSX and Dermo -- favor the same waters.

Trying a new twist on century-old oyster farming practices, Paynter and foundation staffers are planting 200 sacks of empty shells in shallow water around the foundation's 20-acre education center on the southern tip of this marshy Dorchester County peninsula.

If successful, the experiment could help revive the bay's decimated oyster industry, which has seen annual harvests dwindle from a million-plus bushels 20 years ago to just 200,000 bushels last year.

But the research project also holds promise for restoring the bay, because thriving oyster reefs attract other marine life, explained William Goldsborough, the foundation's senior fisheries scientist.

This part of the bay often gets good natural oyster reproduction, but the same conditions that are prime for spawning oysters also aid the parasites. Since the late 1980s, Dermo and MSX have killed young oysters before they could grow to legally edible size.

While some researchers are trying to use biotechnology to produce disease-resistant oysters, Paynter said this experiment is inspired by traditional aquaculture techniques that were commonplace a century ago.

"This is nearly an ancient technique of collecting oysters," Payn- ter said. French aquaculturists in the late 19th century were catching oysters on tree branches they had bound together and anchored in shallow water, he said.

Freshly hatched oyster larvae swim about in the water, but soon begin searching for someplace to settle. Paynter said that shellfish will attach themselves to many different kinds of hard, clean surfaces, though oysters apparently are attracted to each other in ways that scientists do not yet fully understand.

The bags -- each holding about a half-bushel of shells -- were produced and donated by the Oyster Recovery Partnership, a cooperative effort by watermen, aquaculturists and environmentalists that is trying to restore shellfish in Maryland waters of the bay.

The partnership has worked with state officials on producing disease-free oysters at two hatcheries on the Eastern Shore and in Southern Maryland. But when conditions are right, natural reproduction dwarfs the man-made output.

In a good year, each bag could attract up to 1,000 baby oysters, Goldsborough said. Only a fraction of those would survive to maturity under the best of circumstances, he added, but the 200 shell sacks being planted could produce perhaps 2,000 bushels of legally harvestable oysters.

First, though, the researchers have to catch some freshly spawned oysters. Paynter and the foundation staff came up empty-handed this week when they checked five piles of shell bags planted last month.

By this time most summers, oyster larvae should be attaching themselves to hard objects. But this is hardly a normal summer, as snow melt and heavy rains have deluged the bay with fresh water.

Paynter scrutinized the pearly inside of several shells in vain for the speck-sized "spat," or newly attached oysters. Oysters do better in saltier water, and Paynter speculated that the drop in the bay's salinity has delayed the spawning season, which normally runs from mid-May through early August.

Undeterred, the researchers put another 60 shell sacks in the water this week, piling them on wooden pallets to keep them out of the muck on the bottom.

Assuming some baby oysters settle on the shells in the bags, the researchers plan to transfer them in October to the Severn River near Annapolis, where diseases are not as prevalent. The bags are to be placed on an old reef recently restored with shells.

The state's traditional oyster repletion program moves "seed" oysters from where they are spawned in the lower bay to fresher waters, which discourage the growth of the parasites.

Instead of outwitting the organisms, the movement has unfortunately spread them around the bay because the oysters are not moved until nearly a year later, by which time they have become infected.

The researchers hope to succeed by moving the young oysters after just a few months, while they are still no more than a millimeter or two in size. Samples of the oysters will be tested before being transplanted to ensure they are disease-free, Paynter said.

Though barren so far of young oysters, the shell bags already are serving one important ecological role -- as magnets for

aquatic creatures.

On calm days, when the water is clear, fish can be seen loitering around the submerged shell piles, said Scott Culpepper, a Washington College graduate in biology working as an intern at the foundation.

And, as Paynter pulled bags out of the water onto a nearby skiff to check them, tiny crabs, skilletfish and even a slithery eel emerged from the shells.

"We've got all sorts of life here!" exclaimed Jessie Marsh, another bay foundation educator and a former waterman.

Pub Date: 7/17/96

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