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Federal Register / Vol. 86, No. 167 / Wednesday, September 1, 2021 / Proposed Rules
Hickman and Fitz 1978, pp. 1038 and Starnes 1977, entire. The snail darter is well adapted to its habitat of clean gravel substrate in large creeks and rivers. The saddle markings on the back of the fish act as camouflage amongst gravel and small cobble, and are a pattern seen in other benthic species Armbruster and Page 1996, pp. 250
252. Snail darters also can burrow into the substrate with just their eyes exposed to escape predation Etnier and Starnes 1993, p. 588. The species spawns in the late winter and early spring, from about February to April.
Adults gather on shoals during the breeding season. While spawning has not been directly observed, it is likely that the eggs are buried shallowly in the sand and gravel similar to how other Percina species bury their eggs. Females produce about 600 eggs per season during multiple spawning events. Eggs hatch after 1520 days and produce pelagic in the water column larvae that drift considerable distances downstream. The developing larvae and juveniles likely use relatively calm deeper areas of rivers and reservoirs. By the end of summer, juveniles are about 1.6 in 40 mm in length and begin migrating upstream. Some fast-growing individuals may reach sexual maturity in their first year, but most mature in their second year Etnier and Starnes 1993, p. 588. Snail darters are shortlived fish that rarely survive to their fourth year. As their name implies, snail darters mostly feed on freshwater snails, predominantly in the genera Leptoxis and Lithasia, as well as caddisfly and dipteran true fly larvae Etnier and Starnes 1993, p. 588.

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Distribution When we listed the snail darter 40 FR
47505; October 9, 1975, the species was only known from about 13 miles 21
kilometers km of the lower Little Tennessee River in Loudoun County, Tennessee. Shortly thereafter, the species was found in the Watts Bar Reservoir portion of the Tennessee River below the mouth of the Little Tennessee River, and efforts were made to conserve the species by translocating individuals into other suitable streams Hickman and Fitz 1977, pp. 8083. Snail darters were collected from the Little Tennessee River and stocked into the Hiwassee, Holston, Nolichucky, and Elk Rivers beginning in 1975 to achieve this objective. The introductions into the Nolichucky and Elk Rivers were halted when sharphead darters Etheostoma acuticeps, a species once thought extinct, were rediscovered there, causing concern about competition
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between the two species. However, the introductions into the Holston and Hiwassee Rivers were successful, and it is thought that the populations in the French Broad and Ocoee Rivers were established by dispersal from these populations Ashton and Layzer 2008, pp. 5556. These locations are presented on a map in Figure 1, below.
After the completion of Tellico Dam on the Little Tennessee River, snail darters were located in five additional tributaries and three reservoirs: Little River 1983, Big Sewee Creek 1981, Chickamauga Reservoir 1976, Nickajack Reservoir 1981, South Chickamauga Creek Tennessee and Georgia portions 1980, Guntersville Reservoir Tennessee portion 1981, Sequatchie River 1981, and Paint Rock River Alabama portion 1981 Service 1983, pp. 1219; Service 2013, p. 7. A
survey in 2005 located the species in seven of the nine tributaries surveyed:
French Broad River, Hiwassee River, Holston River, Little River, Sequatchie River, Big Sewee Creek, and South Chickamauga Creek Ashton and Layzer 2008, p. 54. This survey appears to be the last known record of snail darters in Big Sewee Creek Simmons 2019, unpublished data. In this survey, snail darters were not located in the Paint Rock River or Ocoee River, though they were discovered at both locations in later years Kuhajda 2018, unpublished data. In 2007, a single snail darter was collected in Citico Creek, suggesting that snail darters may have persisted in the Little Tennessee River watershed after the dam was constructed; however, they were not found in follow-up surveys Service 2013, p. 7.
More recent survey efforts have continued to document new snail darter locations, though with limited information on persistence. In 2012, two snail darters were collected in the Flint River in Alabama Simmons 2019, p. 1, but they have not been found there since. In 2015, snail darters were collected in the Elk River in Alabama and in Bear Creek in Alabama and Mississippi, over 100 river miles 160
km from the Flint River location. To verify these collections, TVA began an effort to survey the mainstem Tennessee River reservoirs for snail darters Simmons 2019, p. 2, collecting snail darters from six reservoirs in Tennessee and Alabama: Chickamauga, Nickajack, Guntersville, Wheeler, Pickwick, and the French Broad River arm of Fort Loudoun Reservoir Simmons 2019, p.
7; TVA unpublished data. Later surveys of the reservoirs located juvenile snail darters in Watts Bar Reservoir Matthews 2020, pers. comm., but
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trawling efforts did not locate individuals in Tellico, Wilson, and Kentucky Reservoirs Simmons 2019, p.
6.
In 2017 and 2018, an environmental DNA survey was conducted for snail darters in the Alabama portion of the Tennessee River Basin Shollenberger 2019, p. 6. Environmental DNA eDNA
is a surveillance tool used to monitor for the genetic presence of an aquatic species. These surveys returned positive eDNA detections in the following streams and reservoirs where TVA
surveys had physically collected snail darters during previous survey efforts:
Guntersville Reservoir, Wheeler Reservoir, Paint Rock River, Elk River, Pickwick Reservoir, and Bear Creek. The eDNA surveys returned negative results at locations where snail darters had not been collected recently, such as Wilson Reservoir and the Flint River, although an eDNA detection was found and then validated in 2020 in Shoal Creek, a tributary to Wilson Reservoir Johnson 2020, p. 2.
In summary, the snail darters known range has greatly expanded since it was first discovered see Fig. 1. At the time of listing in 1975, the species was only known from a small reach of the Little Tennessee River. By the early 1980s, new populations had been found or established in 10 widely dispersed locations, and in 1984, we reclassified the snail darter from an endangered to a threatened species 49 FR 27510; July 5, 1984, due largely to an increased number of populations and a considerable range expansion. Since 2010, populations in an additional two reservoirs and three tributaries have been discovered Simmons 2019, pp. 1
2. As a result, snail darters are now considered extant in seven mainstem reservoirs of the Tennessee River Fort Loudoun, Watts Bar, Chickamauga, Nickajack, Guntersville, Wheeler, and Pickwick and 12 tributaries in the Tennessee River watershed Holston River, French Broad River, Little River, Hiwassee River, Ocoee River, South Chickamauga Creek, Sequatchie River, Paint Rock River, Flint River two individuals, Elk River, Shoal Creek one individual, and Bear Creek. We consider the snail darter extirpated from the Little Tennessee River mainstem, Citico Creek, and Sewee Creek, and never established in the Nolichucky River.
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