For such a tiny fish, the snail darter has haunted Tennessee. It was the endangered species that swam its way to the Supreme Court in a vitriolic battle during the 1970s that temporarily blocked the construction of a dam.

On Friday, a team of researchers argued that the fish was a phantom all along.

“There is, technically, no snail darter,” said Thomas Near, curator of ichthyology at the Yale Peabody Museum.

Dr. Near, also a professor who leads a fish biology lab at Yale, and his colleagues report in the journal Current Biology that the snail darter, Percina tanasi, is neither a distinct species nor a subspecies. Rather, it is an eastern population of Percina uranidea, known also as the stargazing darter, which is not considered endangered.

Dr. Near contends that early researchers “squinted their eyes a bit” when describing the fish, because it represented a way to fight the Tennessee Valley Authority’s plan to build the Tellico Dam on the Little Tennessee River, about 20 miles southwest of Knoxville.

“I feel it was the first and probably the most famous example of what I would call the ‘conservation species concept,’ where people are going to decide a species should be distinct because it will have a downstream conservation implication,” Dr. Near said.

The T.V.A. began building the Tellico Dam in 1967. Environmentalists, lawyers, farmers and the Cherokee, whose archaeological sites faced flooding, were eager to halt the project. In August 1973, they stumbled upon a solution.