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Fish kill on river remains mystery
30% in Cowpasture show infection
BY CHARLES GARRATT • STAFF WRITER
 | | These fisherman on the peaceful, placid, and clean Cowpasture River are not looking for dinner. Department of Game and Inland Fisheries biologist Paul Bugas (left) and Virginia Tech student Toby Coyner shock and net fish last month looking for diseased specimens. Sampling and water testing continue as the fish kill problem lingers through June. (Recorder photo by Charles Garratt) |
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MILLBORO - Fisheries biologist Paul Bugas is worried about the sick and dying fish in the Cowpasture River and he's concerned that more people aren't worried, too.
Bugas, with the Virginia Department of Game and Inland Fisheries, said while the fish kills in the James and Shenandoah rivers have begun to decline in recent days, sampling in the Cowpasture is still turning up a high percentage of sick fish.
Of the samples taken last week near Sycamore Bend Farm and Fort Lewis Lodge, 30 percent of the rock bass and all the dozen smallmouth bass netted had bacterial lesions.
"The sunfish family had issues," Bugas said. The water temperature at both locations was in the low 60s, he said, a bit low for this time of the year.
 | | Last week, fish biologists continued to net bass and sunfish with lesions like these on this bass caught last month from the Cowpasture. The common bacteria causing the lesions has been identified, but the reasons why the fish have suddenly been weakened enough to be susceptible to the bacteria are still a mystery. (Recorder photo by Charles Garratt) |
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The bacteria causing the lesions and fish kills has been identified as aeromonas salmonicida, Bugas said. This is a common bacteria that has been around for decades and decades, he added.
A. salmonicida was first identified in trout at a German fish hatchery in 1890. The bacteria was long thought to be a pathogen only of cold water fish species like trout and salmon.
Varieties of the bacteria are now known to infect warm water species including bass and sunfish and can be a major pest of goldfish in commercial operations and in the wild.
Those investigating the fish kills don't know why fish in the Cowpasture are suddenly susceptible to the common bacteria. Bugas said some of the fish with lesions found last week will likely recover, but he couldn't say what percentage that might be.
The United States Geological Service Fish Health Branch distributes a pamphlet on A. salmonicida primarily to people involved in fish culture, including hatcheries and fish farms.
In the dense populations of fish common in aquaculture, and the bacteria can be a major problem if not controlled. In commercial operations, antibiotics can be used to treat infected fish.
Even in commercial operations, the bacteria do not infect healthy fish. In commercial operations damage to scales from tanks and other fish offer an opening to infection. Factors which stress the fish and weaken the immune system can also lead to infections.
In the James and Shenandoah where the fish kill is declining, Bugas says the water temperature has risen faster than in the Cowpasture. The bacteria causing the lesions "likes cool water," he added.
As the water temperature in the Cowpasture creeps up, Bugas looks for things to slow down and return to normal. "It's going to take a little while," he said, "but if the pattern holds, the river will go into a calming mode."
The real question of what happened in the river to weaken the fish so they became infected with the bacteria still remains.
Bugas is concerned people are not paying attention to what is happening in the river. "These watersheds belong to everybody," Bugas said. "Think of where we would be without them."
Watersheds are used for everything, including being dumping grounds for all kinds of waste. "Some of these rivers are at maximum assimilation point," Bugas said. Fish kills are one way the river has of manifesting itself.
"The biology is trying to tell us something," Bugas said. The Cowpasture is at "yellow stage." Dying wildlife species like fish are a red flag, he said.
"It benefits everybody to have everything in balance," Bugas said. "People need to appreciate their watersheds more. Fresh, clean water is more and more scarce." Bugas believes most people don't understand the importance of clean water to all life.
Don Kain, co-chair of the task force investigating fish kills in the Shenandoah River, appreciates Bugas' concern about public interest. Kain is with the Department of Environmental Quality office in Harrisonburg; the task force is a joint effort of DEQ and DGIF.
The task force has been issuing press releases and seeking assistance from citizens for a number of years. People in organizations like the Cowpasture River Preservation Association, the James River Association and Friends of the North Fork ,are concerned and they offer help.
"We don't know what to do to get the public in general behind it," Kain says. "The rest of the community, the rest of the valley, needs to get involved."
The infected fish in the Cowpasture were first discovered in April as part of routine sampling done in conjunction with studies trying to determine the cause of fish kills in the Shenandoah River watershed.
The Cowpasture was selected by the task force as a "control." Known to be one of the most pristine rivers in the state with similar flows and fish species as the Shenandoah, the task force planned to use the Cowpasture to compare with the Shenandoah in the hopes of finding a cause for the kills by identifying what's different in the two river systems.
In the past month, DGIF personnel have found infected fish in the Maury River near Buena Vista and in the upper James from Horseshoe Bend upstream of Buchanan all the way to Lynchburg. For a number of years, similar fish kills have been reported in parts of the Potomac River watershed in West Virginia.
Scientist at the USGS Leetown facility in Kearneysville, W.Va. have been studying the Virginia and West Virginia fish kills. Last month, technicians collected tissue samples from infected fish in the Cowpasture.
Bugas said more samples were taken last week and some of these will go to Cornell University. Even as infections in the rivers begins to decline, the investigation will intensify. Scientist at Cornell will take a more intensive look at viruses, Bugas said. Fish in the Cowpasture were screened for viruses in 2006, he said, and came up clean.
Kain thinks current data makes a case for a biological cause, such as a virus, to some degree. DEQ will step up studies of water quality, he adds, since nothing can be ruled out at this point.
In addition to diseased and dying fish, a high incidence of intersex has been noted in the Cowpasture and Shenandoah, Kain said. "Intersex" is a term for fish that exhibit traits of both sexes, such as male fish having eggs.
The intersex fish may point to a chemical that acts like a hormone or it may be a normal condition. Some pesticides and industrial chemicals can mimic the effect of normal hormones. Whether this is connected to or related to the fish kills is unknown.
DEQ has a lot of data pending, Kain says. "Virtual fish" were placed in the Cowpasture just before the fish kill began and were in place during the first weeks of the problem. The virtual fish collect chemicals and particles from the river much the way a fish's membranes do. DEQ will send the collectors to a laboratory for analysis.
In addition to collecting and analyzing water and fish samples, DEQ is beginning to do some exposure testing in the laboratory to see if it can create the symptoms, Kain says.
With the huge volume of data already collected and more coming in every day, the task of finding what changed is immense.
As the season warms and the rivers return to normal, Bugas says he is working "to be ready for anything happening next year."
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