Freshwater Mussels in the Powell River
Mussels have a hinged shell like clams and live embedded in the gravels and sands of sections of the river where there is significant water flow. Mussels filter river water through their systems. They are sustained by bits of vegetation, bacteria, algae and digestible detritus that is suspended in the water. They are fed by what’s edible in the river and they are poisoned by what’s poisonous in the river.
There are 33 different species of mussels currently in the Powell River. Fifteen of these species are Federally (or State) listed as “Threatened” or “Endangered,” that is, in danger of going extinct as a species. Some species are relatively common, others are quite rare. Two species only exist in one other river. Some species are smaller than your thumb; some are larger than the palm of your hand. A couple species can live to be up to 75 years old. A few species have been lost to extinction over the last 40 years. The Clinch and the Powell Rivers harbor more species of Federally listed mussels than any other river in the United States. (The Powell River is a tributary of the Clinch River; where it joins the Clinch at Norris Lake, a large TVA managed lake in Northeastern Tennessee.)
They are therefore of interest to biologists and scientists for two reasons: (1) they clean the water of organic matter which would otherwise decay in the river, and (2) they are like canaries in the coal mine – they are an indicator of the aquatic health of the river. If the river is relatively free of harmful toxins, heavy metals, pesticides, excessive sediments, etc., the mussels will thrive. If the river is commonly contaminated with these types of harmful substances, the mussels will suffer and their numbers will fall. Right now mussels in the Powell are slowly coming back from a series of coal slurry spills in the upper reaches of the Powell River in the 1990's and earlier and also from chronic ongoing, though improving, river contamination from mines, farm runoff, and urban sources. The most severe historical impact originated in the Virginia headwaters of the Powell where there is a large concentration of coal mines. One can still easily find light-weight, well-rounded, black "stones" (coal) in the Tennessee portion of the Powell River.
A very interesting fact about mussels is that they depend on fish to incubate their young. Actually fish gills to be specific. To implant the larvae in a fish’s gills requires that the mussel be able to lure a fish into close proximity. Many species of mussel have their own unique form of mimicry. One species has a little flap of tissue that looks exactly like a common river minnow. A smallmouth bass is attracted to the waving bit of tissue and comes close enough to get a gill full of mussels-to-be. When time comes, the mussels drop off at a new place in the river. The fish is unhurt. And the next generation of mussels are able to relocate. Amazing!
Different mussel species employ varying ingenious reproductive strategies.
On September 25, 2012 US Fish and Wildlife Service released 5,000 Federally Endangered mussels at four locations of the Powell River. Approximately 45 people were on hand to watch and to participate in the mussel release including faculty from Lincoln Memorial University, a Regional Director and staff from US Fish and Wildlife Service, Tennessee Wildlife Resources Agency (TWRA) biologists, and scientists from Virginia Tech’s Mussel Lab who actually raised the mussels. Three Film crews were on hand to document this the largest mussel release in the Powell River to date. One of the reasons that US FWS decided to commit this level of resources to the Powell River is because of the mapping, species sampling and water quality analysis that Lincoln Memorial University has produced with the support of the Well Being Foundation.
In October 2016, endangered species of mussels were again released at two sites in the Powell River.