The tiny snail darter makes a big comeback thanks to a decades-long lift from federal biologists.
"Do you know what this is?"
Tennessee Valley Authority aquatic zoologist Jeff Simmons still remembers asking the question to a colleague as they pulled a snail darter from a seine net in 2015.
The two biologists were part of a TVA stream monitoring crew sampling Bear Creek, a Tennessee River tributary some 152 miles downstream of the nearest snail darter sighting, which had occurred in North Alabama's Flint River three years prior.
"I just remember thinking, and no one is going to believe this," Simmons said. "We knew then, the only way these fish could have gotten there was through the mainstem Tennessee."
Just two weeks after the Bear Creek discovery, a TVA crew working in the Elk River recorded its first snail darter sighting after more than 25 years of sampling.
These discoveries prompted a five-year TVA survey that found healthy populations throughout more than 400 miles of the Tennessee River system.
U.S. Fish and Wildlife Service officials reviewed the data and determined the fish no longer merited protection from the Endangered Species Act.
"We've had a long history with this fish," TVA aquatic zoologist Dave Matthews said. "It feels good to know this fish is in good shape now and will be here for years to come. It just goes to show that the Endangered Species Act works."
TVA's 49-year history with the snail darter first began when University of Tennessee ichthyologist Dr. David Etnier discovered the small unknown fish in the Little Tennessee River in 1973.
The darter was declared endangered by 1975 and became the poster child of the Endangered Species Act when a 1978 Supreme Court decision temporarily halted TVA's construction of Tellico Dam.
The Court ruled in favor of the fish. The following year, Congress exempted the Tellico Project from the protection of the Endangered Species Act.
To protect the fish from extinction, TVA state and federal biologists relocated snail darters to various free-flowing rivers in the area prior to the Tellico Dam's completion in November 1979.
TVA's decision to complete the 15,560-acre Tellico Reservoir brought recreational opportunities to the region but created an ecosystem in which snail darters could no longer thrive.
Although additional populations of snail darters were discovered in South Chickamauga Creek in 1980 and in Sewee Creek, Sequatchie River, and Paint Rock River in 1981, sightings of the fish remained scarce and isolated to East Tennessee and North Alabama for 30 years.
TVA biologists suspect snail darters expanded their distribution into the lower Tennessee River system thanks to larval drift.
But understanding what conditions allowed populations to seed and spread after decades of dormancy is more complex.
"When snail darter larvae hatch, they swim up into the water column and develop," Simmons said. "This had been happening for years, but it wasn't until water quality improved throughout the river system that these larvae could actually survive and grow into adulthood on the bottom of the Tennessee River."
Simmons credited the Clean Water Act of 1973 with the initial enhancement of water quality but said the river experienced a further boost beginning in 1991 when TVA implemented both its Lake Improvement Plan and the Reservoir Release Improvement Program.
The two TVA initiatives took a more holistic approach to river management by balancing the competing demands of flood control and power production with the agency's environmental stewardship and economic development initiatives.
TVA established minimum-flow requirements and added oxygen-enriching technologies such as auto-venting turbines, surface-water pumps, oxygen-injection systems, aerating weirs, and low-pressure blowers.
Before the installations, the only way TVA could boost oxygen levels was to spill water over its dams, which did not generate electricity.
"TVA was at the front of these new technologies as they came online," said James Everett, senior manager of the TVA River Forecast Center. "When we installed those systems, they allowed us to maintain oxygen and still reach peak load. They were a win-win because the cost paid for itself through power generation."
By improving water quality and maintaining adequate reservoir flows, TVA helped protect and improve aquatic biodiversity throughout the Tennessee River watershed.
In addition to TVA's initial river-management improvements of the 1990s, the agency conducted further reservoir research in 2004.
Its Reservoir Operations Study had a doubling-down effect on the agency's overall river-management policy as it confirmed the economic and environmental benefits of the previous programs.
The new study reinforced the mission of the TVA Act of 1933 and underscored TVA's commitment to enhance "recreational opportunities while avoiding unacceptable effects on flood risk, water quality, and TVA electric power system costs."
Further improvement measures included TVA's deployment of continuous dissolved-oxygen monitors throughout the watershed. Digital recorders at agency power plants ensured discharge temperatures did not impede the healthy fishery that now supports an annual $12 billion recreation industry.
"We're looking at all that data minute by minute, hour by hour, to monitor oxygen content and make adjustments as needed," Everett said. "Because TVA engineers and scientists have developed this technology, we've seen improvements in river and reservoir health while still keeping true to our flood-control, navigation, and power-generation responsibilities."
Valley-wide operational changes, combined with habitat improvements, benefited many at-risk aquatic species.
These initiatives also benefited Tennessee River mussel populations and provided incentives for the Lake Sturgeon Reintroduction Project.
In addition to oxygen and Tennessee River flow improvements, TVA works with partners throughout the Valley to implement water quality and habitat improvements in its tributaries.
"These partners – leveraging funding and implementing projects such as streambank stabilization – reduce erosion, establish vegetative stream buffers to improve habitat, and remove stream barriers to connect upstream and downstream habitat for aquatic life," said Shannon O'Quinn, senior water resources specialist with TVA Natural Resources and Recreation Management.
"The snail darter's recovery is just one example of how our comprehensive conservation strategy works to preserve these natural resources for the next generation."
In short, the advanced technology and river-management practices ultimately created the conditions necessary for snail darters to migrate.
"The success story here is that we've included protecting biodiversity in TVA's way of operation and policies, which allows native species like the snail darter to exist," Simmons said.
TVA joined multiple state and federal partners at a U.S. Fish and Wildlife Service delisting ceremony at Seven Islands State Park on Oct. 4.
The snail darter is one of only 55 species to have ever been delisted due to recovery.
The Endangered Species Act protects more than 1,300 plant and animal species.
As part of the delisting protocol, TVA will continue to work with U.S. Fish and Wildlife Service officials to monitor snail darter populations for the next five years.
Daniel Elbert, U.S. Fish and Wildlife Service field supervisor for the Ecological Services Program in Tennessee said the recovery of the snail darter is the story of second chances envisioned by the Endangered Species Act and made a reality by a community that solved challenging issues and created an extraordinary outcome.
"It is partners like the TVA who are committed to working together to change the trajectory of species like the snail darter that gives hope to ongoing conservation efforts across the country, and promises that our natural resources will be enjoyed by future generations,” Elbert said.
The Tennessee River and its tributaries harbor 62 federally listed species of fish, mollusks, and crayfish. As ongoing environmental stewardship efforts continue to improve biodiversity across the region, TVA and its state and federal partners hope the snail darter's recovery is the first of many more to come.
"I like to think of our rivers and streams as the arteries of the Tennessee Valley," Matthews said. "We're keeping our finger on the pulse."
Learn more about TVA’s environmental stewardship efforts.