A Mystery of Fish Mortality

What that something is, though, remains elusive. In January, a report from two university professors listed more than 20 theories that might explain the problem. The suspected causes include a virus, pesticides and the dumping of illegal drugs. None of the theories has been proved.

Vicki S. Blazer, a researcher with the U.S. Geological Survey, said a major factor could be manure washed down from the chicken and cattle farms that dot the Shenandoah Valley. Animal waste carries hormones, such as estrogen, that can cause immune problems in fish.

"It overwhelms the fish, is my feeling. But we don't have any proof of that yet," Blazer said.

One piece of evidence supporting this theory is the "intersex" fish found in some of the same rivers: male bass are growing eggs, possibly because of hormone-rich pollution.

A new wrinkle was added to the mystery this year when fish died in the Cowpasture and upper James Rivers in far western Virginia. Both of those waterways are unconnected to the others. For now, nobody can say whether it is the same problem or, if it is, how it traveled overland.

The affected rivers seem significantly changed. Although some fish species, including catfish and carp, have come through unharmed, others, including smallmouth bass and redbreast sunfish, have been devastated. After the 2006 fish kills, state scientists estimated that in sections of the Shenandoah, 80 percent of the smallmouth bass had died.

"I think we're talking millions of fish," said Jeff Kelble, an environmental advocate who is called the Shenandoah riverkeeper.

State officials said they have no way of estimating the total number of fish killed

Even the bass that remain can seem weak and ill. One morning this week, Kelble, a former Shenandoah fishing guide, launched an inflatable boat here into a shallow, deep-green section of river. The scene was pastoral: hayfields on the banks, mountains in the background and great blue herons skimming the surface. But when Kelble reeled in a bass, something was wrong.

"That fish should have a belly," Kelble said, but the stomach, which should have been fat from spring feeding, seemed caved-in and gray. "You see how that's concave? That fish should have a belly there."

Parasites or diseases might have taken advantage of the fish's poor health, Kelble said.

The Shenandoah's famous bass fishery is not officially dead. The president of a local chamber of commerce declared last week, "We are open for business, and the fishing's good."

But the kills have made an economic dent. Last year, a James Madison University researcher estimated that the gruesome kills had scared 2,100 fishermen from the Shenandoah area, at a cost of $686,000 to the local economy and the state.

At Mossy Creek Fly Fishing in Harrisonburg, Va., Colby Trow said many clients -- once drawn by the Shenandoah's famous bass -- had stopped coming.

"They basically just said, 'We'll keep in touch, but we won't be back until that river's clean,' " Trow said.

Instead of driving a few minutes to the South Fork of the Shenandoah, Trow goes 120 miles each way to bring clients to a section of the James River.

Bob Cramer, a fishing guide in Dayton, Va., had been taking clients from Northern Virginia out on the Shenandoah for $300 a day. Now he's helping a friend install invisible pet-control fencing for $75 a day.

But Cramer said the loss was more than financial: It is a sin, he said, that this rural stream seemed to be more toxic than big-city rivers.

"To me, it's just an embarrassment," Cramer said. "We live in such a beautiful place, and we have such terrible water quality."