State biologists are investigating watermen's reports of a major die-off of oysters in the upper Chesapeake Bay that may have been caused by Tropical Storm Lee, a spokesman said today.

"They’re out there on the bars checking to see if the reports are true, and what’s the cause," said Josh Davidsburg with the Maryland Department of Natural Resources. He said officials hoped to have information later this week.

The Annapolis Capital reported Sunday that watermen who've been working in the South River and other local Western Shore waters say their oyster tongs and dredges are coming up full of empty shells.

The early September storm dumped nearly 29 trillion gallons of rain on the mid-Atlantic region, by one estimate, flooding the upper Bay with fresh water and flushing an estimated 4 million tons of sediment into it from the Susquehanna River alone.   The dirt and debris turned the water a chocolate brown, and the surge of fresh water from rivers lowered salinity levels to near zero for weeks after the storm.   Oysters don't grow or reproduce well in water with low salinity, and can even die if trapped in fresh water for extended periods of time.

UPDATE:Davidsburg called back to say DNR biologists are in the midst of checking the upper bay as part of an annual survey of 400 oyster bars in state waters. While not willing to describe the extent or severity of the mortality yet, Davidsburg said, "Preliminary reports show that it's a salinity event."

Larry Simns, president of the Maryland Watermen's Association, said his members say 95 to 100 percent of the oysters are dead along the western Shore as far south as the Bay Bridge.   The Chester River, Eastern Bay and other areas along the Eastern Shore were not hit as badly.  Oysters can only survive about 10 days in fresh water, Simns said.

Oysters farther down the bay appear not to have been greatly affected, if at all.  At the Chesapeake Bay Maritime Museum Oyster Fest in St. Michaels on Saturday, Southern Maryland oyster grower Jon Farrington of Johnny Oyster Seed Co.  told me that salinity levels had dropped alarmingly in the lower Patuxent River after Hurricane Irene in late August, which produced locally intense rainfall.  But the freshet did not last, and his oysters survived, he said.  I noticed that many of the oysters served on the half-shell at the fest came from the Choptank Oyster Co., which raises them in floats near Cambridge. (CORRECTION: Those were being served at one tent - museum spokeswoman Tracey Munson reports the bulk of the oysters served at the fest were wild-caught by members of the Talbot County Watermen's Association. Apologies to them.)

A Deal Island waterman who works Tangier Sound told me there appeared to be a good supply of oysters there, but he was worried about added fishing pressure on them because watermen from up the bay are coming down to harvest there.

(Oysters in tongs; 2008 Baltimore Sun photo by Barbara Haddock Taylor)