The Great Vanishing of Life on the Bay's Bottom

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At the docks on Kent Island in the Chesapeake Bay, Andrew Wright looks over the idled work boats. For 35 years, Wright was a clammer. He worked a hydraulic escalator dredge -- a machine that uses a high-pressure hose and steel conveyor belt to dig up clams from the bottom.

But now both Wright and the old dredger tied up next to him are unemployed because of a sudden and mysterious disappearance of the Bay's clams.

"The clams just got worser and worser. Now it's just, it's gone," Wright said. "Now you can't catch two bushel a day. When I started, we could catch 40 bushel in about three hours... It got down worser and worser. And now it's gone."

Wright ended up losing his livelihood and had to sell his house. He points the finger at himself — blaming overfishing by watermen — and at the hundreds of condos that brought sewage spills and pollution to an historic island community.

If that were the cause of the decline, then the disappearance of the Bay's clams would be a sad but familiar story. But the vanishing of the mollusks is more puzzling and complex than that – and it's a story that not many people know.

"It is a mystery," said Chris Dungan, a scientist with the Maryland Department of Natural Resources.

Dungan (right) is one of the co-authors of a report written for the federal government in January that for the first time documented what it called "unprecedented... catastrophic" deaths of bivalves across the Chesapeake Bay five years ago.

It did not attract public attention at the time. But in late 2003, clammers began to report to state fishery regulators that many of the razor clams they were dredging up were already dead.

Razor clams are narrow and yellow, about the size of a man's thumb, and they are caught mostly as bait for crabs. They hide in long tunnels on the bottom, sticking out pale tentacle-like tubes to suck in and gobble up algae.

When Dungan's colleagues investigated in 2004, they found the deaths were much worse than anyone had guessed. Across Maryland's portion of the Chesapeake Bay, almost 80 percent of all razor clams — once common on the bottom — had died off in a single year, according to the report.

The loss was doubly hard on watermen, because they had only started dredging razor clams about 20 years ago as a last resort — after a disappearance of the Bay's other large clam species: soft clams.

Soft clams, also called white clams or long-necked clams, have thick black siphons and are more oval in shape than razor clams. They are sold to restaurants in New England, where they are called "steamers" and eaten, dunked in butter.

"We know that there huge harvests when the fishery was first initiated about 1950," Dungan said. "And since about 1990, the landings of softshell clams from Maryland waters have plummeted dramatically, to below 100 bushels a year. And during 2006 and 2007, there are actually no official landings of softshell clams for Maryland waters."

Researchers found a tiny parasite – a protozoa called Perkinsus – that appeared to be killing off the soft clams. But it's not clear where it came from. And even more puzzling is the disease that suddenly swept the razor clams (pictured in Dungan's lab, right). The disease appeared to be a leukemia-like blood cancer – scientists call it "DN Disease" -- but they still don't know if it is caused by a virus, parasite, or something else. DN Disease has also infected soft clams.

There's no evidence the diseases are dangerous to people. But the implications of the great vanishing could ripple up and down the Bay's food chain, in part because the estuary's other main filter feeders – oysters— are also nearly gone. Fewer clams and oysters filtering and cleaning the Bay means more algae and murkier waters. And it also means the survival of fewer blue crabs, tundra swans and fish like black drum, because they all eat clams and oysters.

Bill Goldsborough, director of fisheries for the Chesapeake Bay Foundation, said Dungan's report is "very significant." He noted that the disruption of the ecosystem caused by the clam die-off could be complex. For example, with fewer clams to eat, cow-nosed rays will be forced to turn to other sources of food -- such as oysters planted on the bottom in preserves, as part of an attempt to restore that species.

The future for clams in the Bay is not all cloudy. At the same time diseases have been killing razor and softshell clams, in the saltier waters of the southern Chesapeake, watermen have learned to farm a different local species that appears to be resistant to disease — hard clams, including the littlenecks and cherrystones popular in restaurants. There are now about 100 clam farms in Virginia that grow more than 200 million hard clams a year worth at least $27 million.

That's a sign that, at least in some areas, watermen like Andrew Wright can evolve, and rise from their shells — clam dredgers reborn as clam cultivators.

(Drawing of softshell clam (above) courtesy of Maryland Department of Natural Resources website. Photos of Andrew Wright (top) and Chris Dungan (middle) and razor clam in Dungan's lab by Tom Pelton)