Oyster Dredge Results In OXFORD, MD (wypr) - State biologists tracking the Chesapeake Bay's oyster population say they have seen a glimmer of hope in what has long been a dreary picture. WYPR's Joel McCord reports.

Department of Natural Resources scientists say they've seen "reduced mortality" among oysters in Chesapeake Bay for the last five years. Or, in English, oysters aren't dying off as quickly as they had been from the diseases dermo and MSX.

Mike Naylor, head of the department's shellfish division, said three of those five years could be explained by heavy rains that boosted the flow of fresh water into the bay and reduced the salinity. The diseases flourish in saltier water. But that doesn't explain the last two years.

"The last two years we've had a pretty much normal rainfall totals and yet we haven't seen mortality levels return to normal. So that's really encouraging. We're not sure why we're seeing this trend, but we certainly hope that it continues and it bodes well for the future of oysters in the near term."

The results are gathered from surveys like this one aboard the Miss Kay, a DNR research vessel dredging on Stone Church bar in the Tred Avon River off Oxford. Yesterday's trip was for demonstration purposes, but from mid-October to mid-December, the boat works oyster bars from Poole's Island to Tangier Sound.

"This past survey we visited 282 bars, took almost 400 samples--some of the bars we take double samples. And this is our day, just going through this ad nauseum."

Mitch Tarnowski is a shell fish scientist with DNR and editor of the latest report.

He and Robert Bustle pour over a washboard full of oysters, sorting smalls not legal size yet--markets and boxes. Boxes are empty shells, indicating oysters that were killed by disease.

Tarnowski says you can tell a shell is empty just by bumping it against another. It rings hollow.

"In 2002, when we had high mortalities, you drop that, open up the dredge and the contents would fall out of the dredge onto that metal surface and you'd hear the boxes, just the death rattle of the boxes hitting that metal." FADE UNDER SCRIPT

The oysters go to the Cooperative Oxford Lab, where state and federal scientists study diseases in fish, shellfish and other aquatic life. Scientists slice off tiny bits of oyster tissue, treat them and then slice them up even smaller until they get down to pieces the thickness of a single cell.

The whole process takes two weeks from the time the oysters hit the dock until the samples are ready for the microscope. (ROOM AMBI: TRACK 30)

"And what you see are some rather prominent purple spots. And that is the MSX parasite, plasmodium."

Carol McCollough is a natural resources biologist working at the lab. This oyster has MSX for sure, and probably has dermo, but it doesn't show up on this slide.

Neither disease is readily evident to the naked eye. You couldn't tell if the oysters on the half shell at your favorite restaurant were diseased. But McCollough said not to worry, the diseases don't affect humans.

"Generally an oyster that's heavily infected is not very palatable; it doesn't look good, so you're not likely to eat it anyway. But oysters with light infections look very normal. And I'm certain since I eat raw oysters I've consumed a fair amount of dermo and MSX in my life time."

And maybe the oysters themselves are developing some resistance to the disease. . Naylor said with infection rates higher than 60 percent, there is constant pressure on oysters to resist the disease.

"As each individual survives a year it passes along its ability to survive. And the individuals most that are susceptible to disease die off. So they're not able to reproduce."

So, the resistance probably will develop over time, but the time frame probably will be a lot longer than we'd like.

I'm Joel McCord, reporting in Oxford for 88.1, WYPR.
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