Oysters apparently surviving disease at greater rates in bay

Lab expresses optimism despite drought's harm

January 06, 2000|By Joel McCord | Joel McCord,SUN STAFF

Nearly all of 2,000 oysters sampled by state scientists in October were infected with Dermo, one of two diseases that ravaged the Chesapeake Bay oyster population in the early 1990s.

But oysters are surviving at greater rates than in 1992 and 1993, the years of record low harvests, suggesting they are becoming more tolerant of the disease, said Steve Jordan, head of the state Department of Natural Resources' laboratory in Oxford.

"If this holds up, we'll be encouraged," he said.

DNR crews dredged samples from oyster bars from Poole's Island to the mouth of the Potomac River over about four weeks to get a picture of the oyster population.

They found the fifth-highest spat set -- oysters less than a year old -- of the last 10 years, and a bay-wide disease rate of 90 percent, worse than in 1992. They found a death rate of about 34 percent, higher than recent years, but well below the 45 percent of the 1993-1994 season.

The disease rates and death rates were not unexpected, given the lack of rain over the past two years that raised the salinity of the bay, creating conditions ripe for Dermo and MSX. The diseases kill oysters, but do not harm humans.

DNR crews found signs of a harvest in the range of 400,000 bushels -- about the same as the 1998-1999 season, but an improvement over the previous five seasons.

"We're hopeful, said Eric Schwaab, head of DNR's fisheries division, "but we're not ready to unfurl a banner yet."

Oysters are an integral part of Maryland's seafood industry and they are vital to the bay's ecology. They filter pollutants, improving water clarity so that crucial light reaches underwater plants. Their bars and reefs provide habitat for themselves and other organisms.

Oyster landings once averaged 24 million bushels a year, but plunged in recent decades, partly because of over-harvesting and partly because of Dermo and MSX. The harvest bottomed out at 79,618 bushels in the 1993-1994 season and has been recovering slowly.

One sign of that is the growing number of oyster boats in the eastern bay, said Chris Judy, director of DNR's shellfish division.

"There's an active fleet of 20 to 40 boats working every day in there. Three, four years ago, you didn't see any activity," he said.

But those improvements could be lost without an infusion of fresh water to lower the salinity levels, Jordan said.

"It all has to do with rain, and not how much rain falls on the Eastern Shore," he said, but in the valleys of the Susquehanna and Potomac rivers.

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