History of fish kills in the Shenandoah River watershed

2004 l 2005 l 2006 l 2007 l 2008

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2004 - 2005

A fish kill resulting in the loss of an estimated 80 percent of the adult smallmouth bass and redbreast sunfish occurred in more 100 miles of the South Fork Shenandoah River in Virginia between April and July 2005. Nearly identical fish kills were observed in the South Branch Potomac in 2002 and North Fork Shenandoah River in 2004. Biologists with the Virginia Department of Environmental Quality and the Virginia Department of Game and Inland Fisheries have been investigating the cause of the fish kills in the Shenandoah River system.

Several unusual patterns have been found in these fish kills:

• The majority of fish lost were adult smallmouth bass and redbreast sunfish. Juvenile bass and sunfish did not seem to be affected, and other species were only lightly affected.
• The fish deaths were preceded by the formation of bacterial skin lesions, which progressed to the point that the fish finally died.
• The kills began in early spring and continued for two to three months. At any point in time, only low numbers of fish were dying, but the cumulative effect was very severe, killing approximately 80 percent of the adult smallmouth bass and redbreast sunfish.
• The sequence of the fish kills suggests a geographic movement, with the first kill in West Virginia's South Branch Potomac in 2002, the second in Virginia's North Fork Shenandoah in 2004, and the latest in the South Fork Shenandoah River in 2005.
• The kill area occurred throughout the entire length of the respective rivers, with no clear upstream or downstream boundaries.

Fish pathologists at Virginia Tech and the U.S. Fish Wildlife Service examined specimens and determined that these fish were being stressed by undetermined factors and the bacterial lesions were only a secondary effect. Review of water quality data by DEQ did not indicated the presence of any chemicals at toxic levels, although routine samples are collected only once per month. Much of the concern from citizen callers has focused on possible impacts from agricultural, construction and urban runoff.

There has been a high level of interest in these fish kills from the news media, citizens, river guides, environmental groups, and local, state and federal agencies. DEQ and DGIF have maintained close contact with this diverse group of individuals and organizations, both during and after the fish kills. To ensure a collaborative investigative and communication process, DEQ and DGIF formed the Shenandoah River Fish Kill Task Force in July 2005. The task force includes representatives of state and federal agencies, agriculture, industry, riparian landowners, anglers, academia, and citizen environmental groups from the Shenandoah watershed. The group's mission is to evaluate the potential factors resulting in fish lesions and deaths with the goal of determining a cause and communicate findings to those who can promote or implement corrective actions.

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2006

• Spring 2006 efforts
• 2006 monitoring plan
• Governor Kaine announces funds to support investigation, October 2006
• Task Force investigates fish kills, December 2006

The Shenandoah River Fish Kill Task Force investigated reports of fish deaths and fish with lesions in the Shenandoah watershed during spring 2006 and again in December.

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Spring 2006 efforts

• In the North Fork Shenandoah, numerous smallmouth bass and sunfish with lesions were found and a significant number died. The cause was unknown. These problems began in March and continued through May in the lower North Fork, generally downstream of the Woodstock area. There was also a brief fish kill involving smallmouth bass and sunfish in the lower South River near Grottoes in April.
• The task force received no reports of fish deaths in the South Fork Shenandoah in spring 2006. During fish collections in late May, however, about 20 percent of smallmouth bass and sunfish on the South Fork were found with lesions. DGIF and the DEQ continued to monitor these species.
• Also in late May, a large number of northern hogsuckers died in the mainstem Shenandoah between the Route 7 and Route 50 bridges in Clarke County. The task force investigated the cause of this fish kill and collected dead and live fish for examination. Though there were no lesions on the dead hogsuckers, the task force found lesions on redhorse suckers, some smallmouth bass and some sunfish.
• The U.S. Geological Survey studied these fish at its laboratory in Leetown, W.Va., and conducted fish health studies on samples collected earlier from the Shenandoah fish kills.
• The task force also worked with fishery and environmental agencies in West Virginia and Maryland, where fish kills involving suckers were reported this spring on the South Branch of the Potomac and the mainstem Potomac. Most of the dead fish were redhorse suckers, though some northern hogsuckers also died. These kills were similar in timing and types of fish to the one on the Shenandoah River in May.
• The task force, led by DEQ and DGIF, pursued a number of investigations into water quality and fish health in 2006. Preliminary results from these studies did not identify a specific cause of the fish kills, but they suggest that several stress factors affecting fish may be involved. The task force developed a plan and budget request to continue this work through 2007.

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2006 monitoring plan

The task force resumed collecting fish and water samples in March 2006 in the Shenandoah River, the North and South Forks of the Shenandoah, and a reference stream, the Cowpasture River.

2006 work focused on:

• Scattered reports of dead fish and fish with lesions during spring 2006.

• The discovery of fish with male and female characteristics.

The task force evaluated a recent study that found individual fish with characteristics of both sexes, usually identified through microscopic examination of fish tissue. Fish with these characteristics are known as intersex fish. The affected fish were smallmouth bass analyzed by the USGS in 2005 in connection with Virginia's investigation of the fish deaths. Fish from the North and South Forks, the Shenandoah and the Cowpasture had occurrences of intersex. The Cowpasture River was included in the study to help determine background information on fish health. The USGS conducted a similar study in the South Branch Potomac River in West Virginia in 2004 and found the same condition in smallmouth bass. Virginia and West Virginia worked in cooperation with the USGS Leetown Science Center in West Virginia, which has national experience in fish health studies. Microscopic analysis of the testes of some male smallmouth bass revealed the presence of immature eggs. Despite the fish kills and the intersex condition, DGIF fisheries biologists saw good reproduction of smallmouth bass in these waters. Similar fish have been found in other parts of the country, mainly among largemouth bass. (The fish question and answer web page contains additional information about fish with this condition.) There currently is no known correlation between this condition and the fish kills Virginia has experienced. The focus of the task force will continue to be the cause of the fish deaths.

• Daily water quality testing in the North and South Forks.

Among the key investigations in spring 2006 was a comprehensive DEQ water quality study in which daily samples were collected at nine sites on the North and South Forks of the Shenandoah River. (Normally, samples were collected about once a month.) This expanded effort evaluated short-term changes in water quality to identify stressors that are missed during routine sampling. This study intensified during periods of heavy storm water runoff with the collection of samples several times a day at each site.

• Real-time monitoring of water quality.

The USGS conducted real-time monitoring to measure factors such as ammonia, pH, temperature and dissolved oxygen in the North and South Forks every hour around the clock.

• An extensive fish health study of the Shenandoah, North and South Forks, and Cowpasture to seek signs of chronic stress and immune system effects.

DGIF and the USGS, along with the U.S. Fish and Wildlife Service's Fish Disease Laboratory, conducted an extensive fish health study on the Shenandoah, the North and South Forks, and the Cowpasture. Fish were evaluated for indications of stress in their organs, and their blood was analyzed.

The Shenandoah River Fish Kill Task Force also supported additional research as part of its investigation. In summer 2006, researchers from Virginia universities began investigating aquatic insects in the Shenandoah and testing for disease-causing microorganisms using DNA technology. The USGS also began an evaluation of algae in the North Fork and how algae may affect water quality.

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Governor Kaine announces funds to support investigation, October 2006

Governor Timothy M. Kaine announced on October 17 that up to $150,000 is available to support a scientific investigation into the cause of the Shenandoah River fish kills.

The Governor authorized the use of the Virginia Environmental Emergency Response Fund as the source of the additional money, which will help continue research on the fish kills through early 2007. The task force currently is funded through a $200,000 direct appropriation.

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Task Force investigates fish kills, December 2006

The task force, with the assistance of river enthusiasts throughout the watershed, investigated reports of fish kills on the North and South Fork Shenandoah, as well as a fish kill on the mainstem Shenandoah in early December 2006.

On December 11, dead sunfish were found on the North Fork near Passage Creek, and dead sunfish and a smallmouth bass were found on the South Fork in Front Royal.

During the week of December 3, anglers fishing the Shenandoah River between Route 50 and the Lockes Landing access in Clarke County reported seeing numerous dead fish on the bottom of the river. Biologists with DGIF identified the fish as northern hogsuckers and indicated that some of the fish had been dead for several days.

Also that week, the Shenandoah Riverkeeper, members of the Potomac Smallmouth Club, local fishing guides, DGIF and DEQ personnel, riparian landowners, and members of the Shenandoah River Fish Kill Task Force canvassed the South Fork, North Fork and mainstem Shenandoah River to determine the extent of the fish kill. Though observers did find one dead northern hogsucker at one location on the North Fork Shenandoah, the kill appeared to be centered on the mainstem Shenandoah downstream of Morgan's Ford.

The task force contacted West Virginia authorities, who have received no reports of dead fish in the West Virginia portion of the Shenandoah River. At the time, no dead fish were observed on the South Fork Shenandoah.

Biologists will not be able to fully assess the impact to the sucker population until sampling the river in spring 2007. This is the same area of the river where a similar fish kill involving northern hogsuckers occurred in late May 2006. Investigators were not able to determine the cause of that kill.

The task force did not know whether the December 2006 fish kills were related to fish kills that have occurred throughout the Shenandoah watershed in the past three years. Information collected from these incidents will be included in the Shenandoah watershed fish kill investigation.

Fish kills that have affected the Shenandoah, James, Cowpasture and Maury rivers this spring apparently are abating, investigators announced today. This matches the pattern seen in similar fish kills on the North and South Forks of the Shenandoah that began in 2004.

Fish collections this week from the affected rivers have shown fewer problems than those taken earlier in the season, and reports from citizens have been declining. Though scientists have not confirmed any causes of the fish kills, the investigation is making progress and is now concentrating on several key areas.

The Department of Environmental Quality and the Department of Game and Inland Fisheries are coordinating the fish kill investigation. Numerous studies are under way to narrow the focus of possible causes of the fish illnesses and deaths. The current investigation includes:

• An expanded advisory group of scientists to include areas such as fisheries, fish diseases, microbiology, chemistry and agriculture to provide additional expertise for the investigation. DEQ and DGIF expect the panel to be in place in July.
• Analysis of the chemical makeup of agricultural waste streams in the river watersheds. Many of the water quality tests so far have been evaluations of river water and have focused specifically on nutrients and ammonia, which are normally associated with agricultural waste. A plan is under development for expanded, comprehensive testing of waste streams and sources connected with agricultural land uses, with assistance from the Department of Conservation and Recreation. That information will be compared with chemicals found in fish tissue, sediments and water in the fish kill areas.
• Continued evaluation of viruses, bacteria and parasites. This is being coordinated with work by the U.S. Geological Survey, the U.S. Fish and Wildlife Service disease laboratory, and Cornell University. Also, numerous fish collected this spring are being saved for further analysis, after additional chemical information comes in from water quality and agricultural samples.

The task force encourages the public to report any information on the location, number and type of fish found dead or sick in the Shenandoah, Cowpasture and James river systems.

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2007

• Virginia focuses fish kill investigation efforts, March 2007
• Scientists collect fish for fish kill investigation, March 2007
• Task force investigates new fish deaths in Shenandoah watershed, April 25, 2007
• Virginia seeks public's help in fish kill investigation, April 26, 2007
• Fish kill reports on upper James, lower Cowpasture rivers, May 17, 2007
• Fish kills continue; task force expands investigation, June 11, 2007
• Fish kills diminish; Investigation narrows focus, June 15, 2007

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Virginia focuses fish kill investigation efforts, March 2007

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Scientists collect fish for fish kill investigation, March 2007

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Virginia seeks public's help in fish kill investigation, April 26, 2007

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Fish kills continue; task force expands investigation, June 11, 2007

The Virginia fish kill task force has expanded its work to include the Cowpasture, Maury and upper James rivers. Fish that have either died or are ill have been observed in these rivers for the past several weeks.

The fish species mainly affected continue to be smallmouth bass and redbreast sunfish, though other types of fish have been found with sores. The task force, headed by DEQ and DGIF, is coordinating efforts with anglers, conservation organizations and university scientists to identify the location and extent of the fish kills.

In the past three weeks, the number of reports of distressed fish has continued to increase. On the James, the fish have been found as far downstream as Lynchburg. DEQ and DGIF biologists also are investigating new reports from Buena Vista on the Maury River and the mainstem Shenandoah River.

The U.S. Environmental Protection Agency collected sediment samples in late May to test for toxicity and estrogen-related chemicals in some of the rivers. Water samples have been collected from the affected rivers to be tested for known fish viruses. Weekly and continuous water quality monitoring is still under way, and the task force remains in contact with counterparts in West Virginia as they investigate similar fish kills in the Potomac River system.

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Fish kills diminish; Investigation narrows focus, June 15, 2007

Fish kills that have affected the Shenandoah, James, Cowpasture and Maury rivers this spring apparently are abating, investigators announced today. This matches the pattern seen in similar fish kills on the North and South Forks of the Shenandoah that began in 2004.

Fish collections this week from the affected rivers have shown fewer problems than those taken earlier in the season, and reports from citizens have been declining. Though scientists have not confirmed any causes of the fish kills, the investigation is making progress and is now concentrating on several key areas.

The Department of Environmental Quality and the Department of Game and Inland Fisheries are coordinating the fish kill investigation. Numerous studies are under way to narrow the focus of possible causes of the fish illnesses and deaths. The current investigation includes:

• An expanded advisory group of scientists to include areas such as fisheries, fish diseases, microbiology, chemistry and agriculture to provide additional expertise for the investigation. DEQ and DGIF expect the panel to be in place in July.
• Analysis of the chemical makeup of agricultural waste streams in the river watersheds. Many of the water quality tests so far have been evaluations of river water and have focused specifically on nutrients and ammonia, which are normally associated with agricultural waste. A plan is under development for expanded, comprehensive testing of waste streams and sources connected with agricultural land uses, with assistance from the Department of Conservation and Recreation. That information will be compared with chemicals found in fish tissue, sediments and water in the fish kill areas.
• Continued evaluation of viruses, bacteria and parasites. This is being coordinated with work by the U.S. Geological Survey, the U.S. Fish and Wildlife Service disease laboratory, and Cornell University. Also, numerous fish collected this spring are being saved for further analysis, after additional chemical information comes in from water quality and agricultural samples.

The task force encourages the public to report any information on the location, number and type of fish found dead or sick in the Shenandoah, Cowpasture and James river systems.

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2008

• Fish kills have developed more slowly in 2008, Virginia reports, June 13, 2008
• Findings from 2007 fish health studies released, May 19, 2008
• State agencies gear up for potential fish health issues, March 28, 2008
• Fish kill task force evaluates results of latest study, Nov. 18, 2008
  

Fish kills have developed more slowly in 2008, Virginia reports, June 13, 2008

Fish kills are occurring in Virginia rivers again this year but have developed more slowly than in past years, according to ongoing studies by the Department of Environmental Quality and the Department of Game and Inland Fisheries. The severity of the kills in the Shenandoah River watershed may be more moderate this year, though fish kills in the upper James River watershed appear similar to those in 2007, the agencies reported today.

Fish kills and fish with lesions have been observed in the upper James River and some tributaries, including the Jackson and Cowpasture rivers. DGIF sampling on these rivers has confirmed recent anglers' reports that 25 percent to 30 percent of fish have lesions.

There have been no problems reported on the mainstem Shenandoah River, though the upper North and South Forks of the Shenandoah have seen low numbers of affected fish this year. The sections of both forks that experienced kills in past years are reporting greatly improved catches this spring.

Though the fish kills each year apparently have followed the onset of warmer water temperatures during the spring, no cause for the fish deaths and lesions has been identified. The kills have not occurred after June in previous years. The Shenandoah River Fish Kill Task Force, chaired by DEQ and DGIF, began extensive investigations into the problem in 2005.
The number of kills began to increase this spring after stream temperatures rose in late May. Investigators have collected water and fish samples before and during the fish kills, and the same type of sampling has been conducted at other streams in rivers with similar fish species but no fish kills. Laboratory processing of these samples may take several months.
Here is a summary of fish problems reported in 2008:

James River and tributaries

• The upper James River began showing signs of ailing fish in early April. Numbers of dead fish and fish with lesions mostly smallmouth bass and sunfish have increased since stream temperatures increased and stayed warm. Anglers are reporting that fishing remains slow, and many are seeing numerous dead fish on each trip. They also are seeing lesions regularly on the live fish they catch.
• For the first time, the Jackson River is experiencing fish kills. Anglers on the lower Jackson downstream of Covington are providing reports similar to those on the James. Fewer reports have been received from the Jackson than from the James, possibly because there are fewer fishermen on the Jackson.
• The Cowpasture River has generated fewer reports than last year, but the reports all include some lesions and dead fish.
• Craig Creek, a tributary of the James at Eagle Rock, has seen a small number of reports of dead fish and lesions. Fish kills have not been reported on this stream in past years.
  

Shenandoah River, and North and South Forks

• No problems have been reported this year on the mainstem Shenandoah River, downstream of Front Royal.
• Compared to past years, fairly low numbers of dead fish have been reported on the North and South Forks. Lesion rates of 10 percent to 20 percent have been reported in the past several weeks, primarily upstream of the Mount Jackson-Edinburg area on the North Fork and upstream of Elkton on the South Fork.
• Anglers on most sections of the Shenandoah are reporting excellent success and few fish with visible problems. In particular, the lower North Fork from Woodstock to the mouth is producing very good catches this year. The South Fork also is supporting excellent catches in areas that previously experienced fish kills. Sunfish and rock bass, whose numbers were reduced during the kills, appear to be recovering well.

DEQ and DGIF have set priorities for available funds and are coordinating a number of investigations this year. For example, studies in 2008 include sampling before, during and after fish kills in the rivers experiencing those problems. The investigation also is emphasizing rivers where fish kills have not occurred, expanded lists of chemical analyses with a focus on storm flows, and multiple fish health investigations.

The investigating agencies and the fish kill task force encourage the public to provide information on the location, number and type of fish found dead or sick in the Shenandoah and James river systems. Anyone with information is asked to call the DEQ regional office in Harrisonburg at (540) 574-7800, or toll-free in Virginia at 1-800-592-5482. Information also can be emailed to fishreports@deq.virginia.gov.

• 2008 fish report locations (PDF)
• 2008 fish kill reports (PDF)

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Findings from 2007 fish health studies released, May 19, 2008

DEQ and the Department of Game and Inland Fisheries have released a report on the findings from fish health studies conducted during 2007 for the Shenandoah, James and Cowpasture rivers.

• Download report: 2007 Findings: Virginia Fish Kill Investigations (PDF)

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State agencies gear up for potential fish health issues, March 28, 2008

DEQ and DGIF are directing numerous scientific studies and surveillance programs this spring in the western portion of Virginia in preparation for potential fish kills.
Unexplained fish kills and episodes of fish with sores and lesions have occurred during each of the last four springs in the Shenandoah River system. In 2007, similar events also occurred in the upper James and Cowpasture rivers.

The fish kills since 2004 have been unusual, affecting mainly adult smallmouth bass and sunfish. Slow fish die-offs have begun in early April and continued through May. Despite the efforts of many fish health and water chemistry experts, the causes of the fish kills remain unknown.

Studies by state and federal scientists and several university researchers during these fish kills have focused on water chemistry and the health of fish and other aquatic life. Water quality studies to date have targeted nutrients, ammonia and selected organic compounds, but they have not identified any specific chemicals at levels that would be expected to cause the fish kills.

Fish health findings suggest that multiple stressors may be involved, because the symptoms do not clearly indicate any single cause. Fish health and disease experts with the U.S. Geological Survey, the U.S. Fish and Wildlife Service, Cornell University and Virginia Tech have found gill, liver and kidney damage; large numbers of parasites; and signs of bacterial infection. Viral studies have ruled out the likely fish viruses. More detailed investigations focusing on biological sources of disease are planned for 2008.

Since 2004, state agencies and their partners have led multiple investigations into these fish kills. In 2005, DEQ and DGIF formed the Shenandoah River Fish Kill Task Force, an open group of stakeholders, including university and government scientists, environmental groups, fishing guides, and volunteer monitors. This group identified a list of theories on possible causes of the fish kills and methodically reviewed studies to test those theories.

In 2007, DEQ contracted with fisheries experts Dr. Greg Garman of Virginia Commonwealth University and Dr. Don Orth of Virginia Tech to lead a research advisory committee of experts in chemistry, water quality, toxicology, soils science and agriculture. The committee is an independent advisory panel to DEQ and has recently completed a recommended work plan for 2008.

Based on recommendation from the committee and the Fish Kill Task Force, DEQ and DGIF have set priorities for available funds and are coordinating a number of investigations. Studies in 2008 will emphasize additional non-fish kill sites, expanded water quality chemical lists with a focus on storm flows, and multiple fish health investigations. Scheduled projects and lead investigators include:

• Expanded fish health study to evaluate organs, blood chemistry, parasites and tissue contaminants - Virginia Tech and USGS.
• Watershed and fish kill contaminant profile - Virginia Institute of Marine Science.
• Measuring pesticides, organic compounds and heavy metals in storm runoff - James Madison University.
• Measuring organic compounds in the river during the spring using passive samplers, devices which allow measurement of chemicals that are normally not detectable using conventional methods - DEQ and USGS.
• Biweekly analysis of heavy metal concentrations in the rivers during the spring - DEQ.
• Fish kill and fish behavior surveillance by volunteer citizen monitors - task force, state agencies and citizens.
• DEQ and DGIF investigators also are participating in a coordinated study with USGS, the U.S. Environmental Protection Agency, and the West Virginia Department of Environmental Protection on additional fish health studies at several sites within the Potomac River watershed.

If any fish kills are observed this year, the task force encourages the public to provide information on the location, number and type of fish found dead or sick in the Shenandoah, Cowpasture and James river systems. Distressed fish are found mainly in eddies and shallow areas away from the main current.
Anyone with information is asked to call the DEQ regional office in Harrisonburg at (540) 574-7800, or toll-free in Virginia at 1-800-592-5482. Information also can be emailed to fishreports@deq.virginia.gov.

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Fish kill task force evaluates results of latest study, Nov. 18, 2008

The Shenandoah River Fish Kill Task Force met Nov. 17, 2008, to review the latest research on the causes of unexplained fish kills in several Virginia river systems since 2003. Though researchers have not identified a cause, they are evaluating several significant findings and considering several theories. Theories include the possibility of multiple stressors on fish populations that make the cause of the kills more complex than a single contaminant, virus or bacteria. Fish kills mainly have affected smallmouth bass and redbreast sunfish, though the incidence of fish deaths was relatively low in 2008.

Fish kill investigation findings:

• Water quality and environmental conditions
• Analyses of passive samplers (imitation fish tissue)
• Bottom-dwelling stream life
• Fish health
• Bacteria and viruses

Water quality and environmental conditions

DEQ monitored every two weeks from March through May at multiple sites in the Shenandoah, James and Cowpasture rivers, and several comparison streams, for metals. Dr. Dan Downey of James Madison University conducted a study on the South Fork Shenandoah River and a heavily farmed tributary, Cub Run, that evaluated physical and environmental conditions, metals, nutrients, organic chemical, and pesticides. This was done at frequent intervals before, during and after storm events between March and May 2008. The fish kills have occurred mostly during the spring months, starting when water temperatures reach about 59 degrees Fahrenheit in March and April, and ending when temperatures reach the mid- to upper 70s in mid-June. Fish kills appear to be connected to spawning periods for many of the fish species that have been affected. Water quality data from these studies and from extensive sampling during previous fish kill seasons have not identified any contaminants at levels that exceed water quality criteria or known levels of concern for toxic chemicals. This monitoring does not cover every possible water quality parameter, though it does include the most likely potential contaminants.

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Analyses of passive samplers (imitation fish tissue)

Passive samplers were placed at multiple sites in the Shenandoah and Cowpasture rivers in spring 2007 by the Friends of the North Fork and DEQ. Additional samplers were deployed in spring 2008. These samplers imitate fish tissue and chemicals during a four- to six-week period and allow measurements of chemicals that are normally not detected in conventional water samples. A wide range of chemicals were detected and quantified, but no chemicals were found at levels equal to or above known water quality criteria at any sites.

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Bottom-dwelling stream life

Dr. Reese Voshell of Virginia Tech led a multi-year study that evaluated invertebrate communities in the North and South Forks of the Shenandoah and a number of tributaries. Data analyses included comparisons with other large river systems, historical comparisons in the Shenandoah River, and indications whether areas with severe fish kills had corresponding harm to small creatures living on stream bottoms. None of the large river sites in the Shenandoah basin showed significant reduction in biological conditions. The health of small stream creatures showed no patterns that corresponded with areas of heavy fish kills. The data provided no evidence that toxic substances were present in amounts that would cause biological harm. In general, the presence of these creatures in the large river sections appears to be consistent with streams that have high levels of nutrients.

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Fish health

Studies of fish health continued in 2008 by Dr. Vicki Blazer of the U.S. Geological Survey, and Dr. Don Orth of Virginia Tech and associates. Studies focused on fish kill areas in the Shenandoah, James and Cowpasture rivers and included comparison sites in the Rappahannock, New, North Fork Holston and other rivers. Fish were collected before, during and after fish kills. Specimens were examined externally and internally for lesions, general health and abnormalities of skin, gills and internal organs. In addition, parasites were identified and quantified, microscopic analysis was conducted on gills and internal organs, and blood chemistry was evaluated. As seen in previous years, male fish from the Shenandoah and Cowpasture rivers had a high incidence of immature female eggs in the testes, known as intersex. The studies suggest that a wide variety of parasites, bacteria and viruses caused infections in fish that died. It is not known whether fish kills and reproductive issues are linked. 

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Bacteria and viruses

In 2008, Dr. Rocco Cipriano of USGS conducted bacterial analyses on numerous specimens from fish kill and comparison sites before, during and after kills in the Shenandoah, James, Cowpasture and other rivers. Cultures were obtained from skin, gills and internal organs. The findings show that pre-kill fish had diverse types of bacteria, but no symptoms. Once the fish kills and symptoms such as skin lesions began, the dominant bacteria shifted to Aeromonas salmonicida. When fish kills ended in mid- to late June, the bacteria in fish from the rivers with fish kills returned to the diverse groups seen before the kills. Specimens examined from streams without fish kills did not appear to host Aeromonas salmonicida at any time, even when fish kills were occurring in other rivers. Aeromonas salmonicida causes furunculosis, a disease with symptoms consistent with those observed in dead and dying fish in the Shenandoah, Cowpasture and James rivers. However, the investigation has not determined whether the bacteria caused the fish kills or is related to them.

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