Clinch River mussel pulled back from the brink of extinction
A chemical spill, innovative science and a McDonald’s parking lot
Richlands, Virginia - In late August, 1998, a tanker truck carrying a chemical used to make foam rubber overturned on U.S. route 460 spilling its contents into Virginia’s Clinch River. That spill killed stream animals for miles, including more than 7,000 mussels, mainly between the towns of Cedar Bluff and Richlands.
Before the spill, the only place in the world where the golden riffleshell mussel could be found was the Clinch River and one of its tributaries, Indian Creek. The spill eliminated the mussel from the Clinch, meaning the estimated 400 individuals holding on in about a mile of Indian Creek were all that remained in the world. Nearly twenty years later, this number had dwindled to the point that biologists with the Virginia Department of Game and Inland Fisheries were having trouble locating more than just a handful over the course of several weeks of effort, and most feared the mussel’s extinction was imminent.
The plight of the golden riffleshell, which is listed as endangered under the Endangered Species Act, took a leap forward on September 21, as 700 captively-reared individuals were released into three sites – on Indian Creek, and on the Clinch River on the edge of Richlands, Virginia, and further upstream at a site owned by The Nature Conservancy. Site selection came after biologists put a small number of the mussels at five different sites in the river for several months, repeatedly checking the animals for survival and growth before risking placing significant numbers of the imperiled mussels into the wild.
“It’s remarkable to see an animal get this close to extinction, and see such an effort to bring it back,” said Jordan Richard, of the Service’s Abingdon Field Office. “Without the efforts of dedicated staff at state agencies, universities, and non-governmental organizations working collaboratively with the Service, the reintroduction of the golden riffleshell would not have been possible.”
Although tremendous strides have been made in the ability to captively propagate and rear rare mussels for stocking into the wild, standard techniques proved challenging with the golden riffleshell, dimming hopes of restocking the Clinch River. After years of effort with limited success, the state of Virginia looked to neighboring Kentucky, and a little-known technique that proved to be key.
“There were doubts it would be possible to raise this species in captivity, but fortunately innovation on the part of Kentucky biologists saved the day,” said Andrew Henderson, the Fish and Wildlife Service’s lead biologist for the mussel.
Freshwater mussels spend their larval stage attached to fish gills, which provide them with the nutrients needed to develop into young mussels. Monte McGregor, director of Kentucky’s Center for Mollusk Conservation, was familiar with the golden riffleshell from working in Virginia, and had also led a team that developed a way to develop the larval mussels in a nutrient bath, cutting out the need for a temporary fish host – his lab one of only a handful in the nation with this ability.
In 2016, Virginia Department of Game and Inland Fisheries biologists could find only three female golden riffleshell mussels in the wild that were carrying larval young. They placed these mussels in a holding tub and drove them to a McDonald’s parking lot in Pikeville, Ky., where McGregor met them and extracted the larvae, placing them in petri dishes with his nutrient bath. The adults were quickly returned to the river, and over the coming months, McGregor’s lab successfully raised 1,600 young mussels. Using the nutrient bath instead of a host fish proved key. Most of these mussels were transported to Virginia’s Aquatic Wildlife Conservation Center in Marion, Va., where they were grown to adult size. McGregor thinks the released mussels may begin reproducing as early as this fall. Biologists are keeping 300 mussels in captivity to start a captive breeding program in anticipation of future stocking efforts.
Though the stocking of these mussels is a significant milestone in bringing the species back from the brink of extinction, the episode highlights the tenuous nature of stream water quality. While the chemical spill was a lone, rare incident that stressed how quickly and easily stream health could collapse, these mussels are endangered as a result of a long, slow decline resulting from years of habitat loss and low-grade water quality issues.
“Boosting the wild population by releasing these animals buys us with more time to focus on the species’ recovery – time that we weren’t sure we were going to be afforded”, said Tim Lane, the southwest Virginia mussel recovery coordinator for the VDGIF. “By no means is the species out of the woods, just yet. It will take multiple efforts like this over many years to provide adequate numbers for the population to again function naturally. We are thankful for the cooperation and expertise of biologists at partnering agencies, including: the U.S. Fish and Wildlife Service, Kentucky Department of Fish and Wildlife Resources, Virginia Tech University, and the Nature Conservancy. Now it depends on the citizens of Cedar Bluff and Richlands to help our agency protect this unique and valuable resource for future generations.“
The Clinch River, which begins in southwest Virginia and flows southwest into Tennessee, is renowned for the incredible diversity of life in its waters, especially freshwater mussels. Several other federally threatened and endangered mussels are found in the Clinch River, including the Tennessee bean, rough rabbitsfoot, Cumblerlandian combshell, oyster mussel, fluted kidneyshell, and slabside pearlymussel. In addition to being home to a tremendous diversity of life, the Clinch River is a growing river destination for paddlers. The diversity of life, and the river as an outdoor destination and source of income from paddlers, depend on a healthy river, which in turn depends on solid stewardship.
Stream health and water quality is about far more than mussels. Freshwater mussels are indicator species - their well-being reflects the health of the stream where they live. Therefore, when mussels are abundant and doing well, it means the stream is healthy, which in-turn is important to everyone from anglers, to paddlers, to even towns that use streams as a drinking water supply for their residents.
The golden riffleshell was only recently identified by scientists, after genetic analysis revealed tan riffleshell mussels in the Clinch River and Indian Creek were different than those in the Cumberland River system of Tennessee and Kentucky. The Clinch River/Indian Creek population became a separate subspecies, the golden riffleshell; while the Cumberland River population maintained the tan riffleshell common name.
Gary Peeples, firstname.lastname@example.org, (828) 258-3939, ext. 234
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