Marbled Darter (Etheostoma marmorpinnum) Status: Listed as endangered (as part of the Duskytail darter group) in 1993 Range: Six river miles of the Little River, Blount County, TN Population: Fewer than 1,000 ________________________   Tan Riffleshell (Epioblasma florentina walkeri) Status: Listed as endangered in 1977 Range: The only reproducing population is found on two-kilometer reach of Indian Creek, a tributary of the Clinch River in southwest Virginia Population: The current population is unknown. In 2001, the population was determined to be approximately 2,000 adults.

The Tennessee Watershed incorporates numerous manmade reservoirs, nine major rivers, and countless tributary streams and creeks that flow through the state. These hundreds of thousands of lake acres and some 60,000 river-miles sustain Tennessee’s communities, provide recreation, support the state’s economy, and are home to an extraordinary variety of aquatic species, including a significant number of endangered species. The watershed is particularly important to two groups of imperiled species—darters (small, non-game fish) and mussels. The Little River, which rises from the highest elevation in the state and flows for approximately sixty miles before emptying into Fort Loudoun Lake, is the only remaining habitat of the marbled darter. The Clinch and Powell rivers, which flow from the Appalachian Mountains of southwestern Virginia, are the only remaining undammed headwaters of the Tennessee River system, and the Clinch River basin, which is home to at least thirty-five mussel species, is one of the most critical hotspots in the nation for imperiled species, including the tan riffleshell.

The marbled darter is a small and short-lived fish, with a typical lifespan of just one year; because of this, the darter usually has only one opportunity to spawn. Females lay multiple clutches of eggs on the underside of slabshaped rocks in the slower-moving waters of the Little River, and the males guard the eggs. Both young and adult marbled darters live in slow runs and pools, and require relatively silt-free cover and plentiful aquatic insects for feeding; the darter’s diet includes mayfly nymphs and other larvae. Marbled darters were originally identified by a single specimen found in the Holston River in Tennessee; they are now extinct in the Holston, and are found only in the lowermost six river-miles of the unimpounded portion of the Little River in Blount County, Tennessee. Conservation Fisheries is captively propagating marbled darters in hopes of establishing additional populations further upstream in the Little River, with the longer-range goal that populations will be reestablished in the Holston River, as well.

The tan riffleshell is a small freshwater mussel with a brown- to yellowcolored shell with numerous green rays. These tiny shellfish make a living by eating small particles suspended in the water, serving to clean and restore nutrients to their habitat. Tan riffleshells belong to the genus Epioblasma, which are the most endangered unionids in the United States. As of 2001, all but one of the remaining species in the genus were listed as endangered. Once widely spread throughout rivers and lakes in Tennessee and southwestern Virginia, the tan riffleshell is now on the edge of extinction. The only known population includes fewer than 1,000, and is isolated in less than a two-mile reach of the Indian Creek tributary of the Clinch River in southwest Virginia. Since 2002, the National Park Service has collaborated with the U.S. Fish and Wildlife Service, other state and federal agencies, and two mussel hatcheries to breed freshwater mussels, including the tan riffleshell, and reintroduce them to the Clinch River habitat.

Water in the Balance

While this watershed is widespread, covering much of the state, it is significantly altered. The Tennessee Valley Authority currently operates twenty-nine dams on the Tennessee River and its tributaries, making it one of the largest hydropower systems in the world. Dividing up the river and its tributaries in this way has caused species populations to become highly isolated, with no suitable habitat corridors to connect the populations. Species with small isolated populations have become particularly vulnerable to water quality threats.

Both the marbled darter and the tan riffleshell are significantly threatened by water degradation in their respective habitats. The marbled darter, which, like the tan riffleshell, serves as an ecological indicator, has been heavily impacted by agricultural practices in the Little River watershed—including the use of pesticides, herbicides, and fertilizers—and especially by increasing amounts of silt in the river. The darter is further affected by commercial and residential development, both of which pollute the darter’s habitat with large quantities of silt from construction and unpaved roads. Recreational overuse of the river by tourists upstream of the marbled darter’s habitat also contributes to the degradation of their fragile habitat.

Once one of the healthiest and most diverse streams of its size in the country, the Clinch River and its many tributaries, including Indian Creek, are heavily threatened. Fossil fuel development, bridge construction and maintenance, and construction of TVA and Corps of Engineers dams decimated populations of the tan riffleshell in Tennessee, Virginia, and Kentucky. The last remaining reproducing population, found in a short stretch of the Indian Creek, is primarily threatened by hazardous byproducts of the coal-fired power plants and the coal mining industry in the greater Tennessee watershed. Repeated spills of sulphuric acid and heavy metals from mining have compounded contamination in the Clinch River and its watershed. Illegal discharges of coal ash (also known as fly ash), which contains a number of deadly toxins, continues to impact both ground and surface waters, heavily polluting this species’ small and fragile habitat. Like all freshwater mussels, the tan riffleshell is a proverbial “canary in the coal mine.” When these filter feeders are inundated with sediment and pollution, and entire colonies die off, alarm bells should be ringing.