The snail darter (Percina tanasi) is a small species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is found in East Tennessee freshwater in the United States. First recorded in 1973, the snail darter was listed as endangered under the U.S. Endangered Species Act of 1973 by 1975. The species was at the center of a major environmental law controversy that involved a lawsuit seeking to halt the completion of Tellico Dam, which posed a risk of extinction for the snail darter by blocking its migratory route. The case was eventually appealed to the U.S. Supreme Court, which ruled on it in its 1978 decision Tennessee Valley Authority v. Hill. In 1978, the U.S. Fish and Wildlife Service, Tennessee Valley Authority (TVA), and Tennessee Wildlife Resources Agency launched a recovery plan to preserve the snail darter by transferring the species to other river systems. Its native range was originally in the lower parts of the Little Tennessee River, the Sequatchie River, and in Chickamauga Creek, but was later eliminated from the Little Tennessee River by the completion of Tellico Dam. The species was then transplanted into the Hiwassee River in southeastern Tennessee. The species inhabits large creeks or deeper portions of rivers and reservoirs with gravel and sand shoals substrate. The snail darter spawns between February to mid-April with the female producing 600 eggs which drift downstream. Juveniles occupy slack water habitats and migrate upstream to the breeding ground. The lifespan of the snail darter ranges between 2 and 4 years. The snail darter adult length ranges between . The species’ diet consists mostly of snails and insects (caddisflies, midges, and blackflies). Snail darters have camouflage dorsal patterns and burrow in the substrate to conserve energy and hide from predators. They are largely preyed upon by banded sculpin (Cottus carolinae). The specific name tanasi derives from capital of the Cherokee Nation located on the Little Tennessee River where the species was first recorded. The species was relisted as threatened in 1984 after being successfully transplanted into other river systems. Geographic distribution The original range of the snail darter was thought to be strictly in the lower portion of the Little Tennessee River with a few individuals dispersing into the headwaters of the Watts Bar Reservoir below Fort Loudon Dam. Prior to the completion of