The snail darter is a small (up to 9 cm long), rare fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 found in the waters of East Tennessee

East Tennessee

East Tennessee is a name given to approximately the eastern third of the U.S. state of Tennessee, one of the three Grand Divisions of Tennessee defined in state law. East Tennessee consists of 33 counties, 30 located within the Eastern Time Zone and three counties in the Central Time Zone, namely...

. It is a variety of darter

Darter (fish)

The fish popularly known as darters are small perch-like fish.They inhabit freshwater streams in North America. They are members of the family percidae and include members of the Ammocrypta, Crystallaria, Etheostoma and Percina genera....

 which feeds primarily on aquatic snail

Snail

Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s.

The snail darter was initially native only to the Little Tennessee River

Little Tennessee River

The Little Tennessee River is a tributary of the Tennessee River, approximately 135 miles long, in the Appalachian Mountains in the southeastern United States.-Geography:...

. It was discovered in 1973, and subsequently was at the center of a legal controversy

Snail darter controversy

The snail darter controversy involved the delay of the construction of the Tellico Dam on the Little Tennessee River in 1973. On August 12, 1973, University of Tennessee biologist and professor David Etnier discovered the snail darter in the Little Tennessee River while doing research related to a...

 in which construction of the Tellico Dam

Tellico Dam

Tellico Dam is a dam built by the Tennessee Valley Authority in Loudon County, Tennessee on the Little Tennessee River just above the main stem of the Tennessee River. It impounds the Tellico Reservoir....

 was delayed due to concerns that it would extirpate the species. The snail darter was declared an endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 in 1975 under the U.S. Endangered Species Act

Endangered Species Act

The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

 (ESA) of 1973; this halted construction of the dam for two years, until an amendment to the Act officially exempted Tellico. The snail darter was later introduced successfully to the Hiwassee River

Hiwassee River

The Hiwassee River has its headwaters on the north slope of Rocky Mountain in Towns County in northern Georgia and flows northward into North Carolina before turning westward into Tennessee, flowing into the Tennessee River a few miles west of State Route 58 in Meigs County, Tennessee...

. On July 5, 1984, its status was lowered to threatened

Threatened species

Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...

.