Fish Kills in the Shenandoah River

Numerous environmental issues have surfaced in recent years as both direct and indirect results of growing populations and urban sprawl. Expanding communities, new business, and new industries are continuously being constructed in newly developing areas. Pollution, erosion, and destruction of habitat are some of the most common environmental issues which are regularly encountered in developing areas. One particular area of interest is the rapidly expanding area in and around the Shenandoah watershed. In recent years, fishermen and scientists have been observing lesions on smallmouth bass and redbreast sunfish removed from the waters of the Shenandoah. Fish kills were also first observed in the Shenandoah in 2004, and they have been ongoing since. Research is being conducted to link the fish kills and lesions to a specific cause, but scientists have been unable to pinpoint a cause for the problem at this time. The presence of these lesions along with the recurring kills lead scientists to believe that the conditions exist due to some newly surfacing environmental problem in or around the watershed. Environmental planning and action will be necessary to correctly identify the problem, link the problem to a specific source, and plan to take action to correct and prevent the problem.

The first fish kill in the Shenandoah River was observed in the spring of 2004, and more kills have occurred since. A fish kill removed nearly 80 percent of the adult smallmouth bass population in 2005. As locals and fisherman began to notice these mass numbers of dead fish along the riverbanks, more attention was drawn to the problem. Scientists began to observe that smallmouth bass and redbreast sunfish began to develop lesions on their bodies in the spring while they were spawning. Further research showed that the fish affected with lesions also had suppressed immune systems. Some affected fish were found alive but obviously dying. These fish also had the same lesions as the dead fish, and they appeared to swim aimlessly as if drunk. Since scientists were unable to determine a direct cause of these problems, further research was conducted following the 2005 fish kill. This research led scientists to discover the presence of inter-sex fish in the same areas where the fish with lesions occurred. These two problems are likely interrelated. Further studies were conducted to assess the sexual and seasonal variations in muscle tissue of smallmouth bass in the Shenandoah. These studies showed significant relationships between mercury levels and length, weight, and age of the fish observed. Studies also showed that mercury levels also varied greatly between sexes in the fish. More recently, fish kills are still occurring in Virginia’s rivers, but they are developing more slowly this year according to the Department of Game and Inland Fisheries. The severity of the kills in the Shenandoah watershed is more moderate this year, and around 30 percent of the fish in the James River have lesions. The fish kills tend to follow the onset of warmer water temperatures each year in the spring. Due to this wide range of problems observed in the fish it has become difficult for scientists to point out a specific cause at this time. Therefore, extensive research is being done at this time to investigate a number of potential causes in order to correctly identify and treat the problem.

Researchers are investigating a number of potential causes of these lesions and kills in the Shenandoah. Although the exact source of the problem is still unknown, several theories have been developed and the fish kills are likely a result of a combination of some of these possible causes. Since most fish kills occur as a result of oxygen depletion, scientists looked into this issue initially. Oxygen levels in the water depend on the water temperature, depth, and the amount of water movement. High nutrient levels in the water can easily lead to oxygen depletion. High nutrient levels may have likely resulted in the Shenandoah as a result of over fertilizing. Nutrients, sediments, and toxins were also expected to contribute to poor water quality in and around the Chesapeake Bay area. Herbicides and degradation products were the most frequently detected chemicals when tests were conducted, and the herbicide degradation products were the toxins occurring in the highest concentrations. Exposure to these products as well as other agricultural chemicals can easily result in fish mortality. The south fork of the Shenandoah also had tests conducted for the presence of similar toxins. There was bacterial impairment detected in the river concerning fecal bacteria which exceeded state standards. This is likely a result of sewage contamination or agricultural runoff. Another potential cause of the kills other than toxins and agricultural runoff is the rapid, poorly planned development on the land near the Shenandoah. This development is such a threat to the Shenandoah River that it has become the fifth most endangered river in the nation. The most endangered rivers report suggests that the poorly planned development may be linked to the recent fish kills and lesions. One other potential cause being further examined is the presence of pharmaceutical chemicals in the water. This is a possible problem linked to the characteristics of both sexes in fish which was recently observed. Also, the highest severity of lesions was noted during the spawning season. This led researchers to believe that the lesions along with presence of inter-sex fish indicated exposure to estrogenic compounds. This may be a result of the presence of pharmaceuticals such as birth control in sewage and water. Although, scientists have yet to confirm a direct cause, these problems are likely a result of one of these environmental impacts or a combination of a number of impacts.

Research and studies are still being conducted in areas in and around the Shenandoah River watershed. The fish kills are still occurring, and fish with lesions are still being discovered in the Shenandoah and James rivers. Investigators will continue to collect fish samples to investigate the fish kills that have plagued the Shenandoah for the past several years. Members of the Department of Environmental Quality, Department of Game and Inland Fisheries, the U.S. Geological Survey, and Virginia Polytechnic Institute and State University will be collecting samples and participating in investigations. The studies are funded by $200,000 in state appropriation. Virginia Tech is involved with implementing the use of “virtual fish” to assist with monitoring and investigation of the river. As studies continue, the potential causes will be uncovered and researches hope to fully understand the problem. Once scientists are able to pinpoint a specific cause of the fish kills, environmental planning will be necessary. Some environmental policy will likely be required to regulate the agriculture and development in the area since these are causes likely responsible for the fish kills. Stricter policies for toxins, fertilizer, pesticides, herbicides, and other agricultural runoff may be implemented. Also, some stricter zoning ordinances and construction regulations might be necessary to prevent heavy environmental impact due to rapid construction and development in areas.