Maryland agency's oyster assumptions don't jibe with bay scientists' research


July 25, 1992|By TOM HORTON

Of all the visions and strategies for restoring the Chesapeake Bay, none is more compelling than the oyster scenario that has emerged in both the scientific and popular literature of the past few years. It goes like this:

* Until massive overfishing began a century ago, so many oysters populated the bay that ships grounded on the reefs they created. Now the population has shrunk by up to 99 percent.

* The reefs have been ground flat by dredges and hydraulic tongs. The hard, shelly bay bottoms that oysters need to grow are more than half silted over.

* We have lost far more than seafood, or watermen's livings. We also have nearly destroyed a giant biological filter. When they feed,oysters suck water through their gills, removing the very pollutants that deplete oxygen and sea grasses throughout the estuary. Once there were enough oysters to filter all the water every week or so. Now the task takes months.

* This means that cleansing the bay is not just about techno-fixes to sewage plants and industrial discharges. If we allow over-stressed natural systems to rebound, the bay can help take care of itself. Moreover, restoring oyster reefs has side benefits no sewage upgrade can ever match: creating habitats for sport fish, crabs and hundreds of other creatures.

Given this scenario, it's no wonder that environmental groups, private citizens, federal agencies and private industry have begun exploring ways to dramatically increase the numbers of oysters in the bay as a means of enhancing water quality. It appears to be one of those "win-win" solutions.

It also could be dead wrong, according to a controversial opinion now emerging from the Maryland Department of Natural Resources (DNR) unit that manages the bay's oysters. In this view, the population never actually declined as much as was believed; therefore, counting on a huge oyster recovery is unrealistic.

The prevailing wisdom that the bay's oysters have been reduced from some golden age of superabundance to a vastly more degraded state in modern times is so far overblown it verges on "fantasy," says William P. Jensen, DNR's longtime fisheries director.

His department has reanalyzed records of the legendary oyster harvests of old to exclude small shellfish that could not be legally kept under more modern size limits. And the department has used new and better methods of sampling current oyster populations. All the work points to a smaller decline during this century than was assumed.

The loss of oyster reefs and shelly bottom habitat also has been far less dramatic than scientists believe, Mr. Jensen says, adding: "This bay is still incredibly productive of oysters."

DNR's assumptions, based on research by a staff scientist, Mark Homer, are at considerable odds with several papers published by oyster scientists at the two University of Maryland bay laboratories and the Virginia Institute of Marine Science. The DNR research leads it to conclude that overfishing by oystermen is not a problem now, and has not been since the early dec

ades of this century.

Oyster harvests have indeed plummeted to historic lows in the past decade, but the reason is purely the oyster diseases that have invaded the saltier portions of the bay, DNR says. But UM research suggests that while disease is a major factor in oyster declines, restrictions on oystering are essential to recovery -- though unpopular politically.

This debate raises a fundamental question: Are we managing oysters for watermen or for the health of the bay?

If, as some university scientists argue, oysters are now occupying only 1 percent, or a small fraction, of their former ecological role as a water filter, then we must set aside major oyster sanctuaries, or consider a temporary end to watermen's harvests for the greater public good.

If, as the state thinks, there are still massive numbers of oysters out there, then we needn't delve into the stupefying political controversies that have always accompanied attempts to restrict oystering.

Contrary to what you might think, the debate about oysters could actually mean progress. Until now, DNR has rejected most outside science and expert opinion on the ecological potential of oysters to enhance water quality. With Dr. Homer's research, Mr. Jensen now is attempting to justify scientifically the assumptions on which he has pretty much operated all along.

Can Mr. Jensen make the case? Experts who have seen presentations of Dr. Homer's work say they cannot analyze it fully until the work is published.

At a recent meeting where oyster scientists heard DNR's new theories, "everyone's jaw dropped . . . some of what they were claiming just seemed unbelievable to us," recalls Roger Newell, a UM scientist who believes oysters once filtered and cleansed bay waters much more efficiently than today's stocks of the shellfish.

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