- The Washington Times - Sunday, December 28, 2008

ROANOKE | Scientists studying the large number of dead fish in several of Virginia’s western mountain rivers say they have promising leads but not definitive answers.

Tests of dying fish this year in the Shenandoah, upper James and Cowpasture rivers revealed the presence of a strain of bacteria that causes a disease with symptoms such as the cigar-burn-like lesions found on the fish.

While the discovery of the bacteria Aeromonas salmonicida could be significant, it raises even more questions than scientists already were asking about the fish kills, said state Department of Environmental Quality biologist Don Kain.

One issue: This type of bacteria is most commonly found in fish that inhabit cold northern waters, such as salmon or trout. Virginia has trout streams that run into the Shenandoah and James, Mr. Kain said, but no trout have died.

Most of the fish affected in Virginia were smallmouth bass or redbreast sunfish. Fish kills have been recorded over the past five years in the Shenandoah River and the past two in the James and Cowpasture, though the numbers were smaller this year.

Scientists found that the bacteria strain was present in the dying fish but not in the water and not in fish before or after the kills.

Could this bacteria, which causes a disease called furunculosis, be responsible for the kills?

“The answer is maybe,” Mr. Kain said. “Right now there appears to be a strong association, which is not the same as cause and effect.”

One question that major biologists need to answer is whether the fish were already dying when they were infected by the bacteria.

The goal next year will be to learn whether Aeromonas salmonicida is causing the kills and how it is getting to fish in these rivers.

State scientists will get help from a U.S. Geological Survey scientist who is familiar with the strain, Mr. Kain said.

This strain of bacteria cannot live in water warmer than roughly 77 degrees. The upper James, the Shenandoah and the Cowpasture typically are warmer than that during the summer. So Mr. Kain said the organism either may be living in feeder trout streams that stay cool or is being reintroduced into the rivers every spring.

That leads to the question of how it’s getting into the fish. The strain could be carried by wildlife such as birds, Mr. Kain said, or in fishermen’s bait buckets.

However, tests so far have shown no presence of the bacteria in fish in the Maury River, which is between the Shenandoah and the James.

The poultry industry has received increased scrutiny since the unexplained kills began. But one task-force finding appears to absolve agricultural runoff. And other aquatic life remains unharmed.

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