Fish
Snail Darter
Percina tanasi · also called snail darters
A fish barely longer than a finger, picking snails off a gravel riverbed in Tennessee, once stood at the centre of a US Supreme Court case that stopped a nearly finished federal dam in its tracks, a legal fight that made the snail darter one of the most famous fish in American history.
Overview
The snail darter, Percina tanasi, is a small, snail-eating fish native to clean, flowing river shoal habitat across several tributaries of the Tennessee River system in Tennessee and Georgia. Its central role in a landmark Endangered Species Act court battle, specialised snail diet, and eventual full recovery and delisting make it one of the most historically significant small fish in the United States.
A tiny fish that changed environmental law
When construction of the Tellico Dam threatened to destroy the only known habitat of a fish scientists had barely finished describing, the resulting legal battle helped define how far the Endangered Species Act could reach, regardless of a species’ size or economic importance.
Status
Least Concern and formally delisted from the US Endangered Species Act in 2022, following successful relocation to additional Tennessee River tributaries and decades of population recovery.
Snail Darter: common questions
Why is the snail darter famous?
The discovery of this small fish in the Little Tennessee River in the 1970s became the centre of a landmark US Supreme Court case, Tennessee Valley Authority v. Hill, which temporarily halted construction of the nearly completed Tellico Dam under the Endangered Species Act, making the snail darter one of the most widely recognised examples of endangered species law in American history.
Is the snail darter still endangered?
No, the species was formally removed from the federal endangered species list in 2022 after decades of recovery efforts, including the successful relocation of populations to several additional Tennessee River tributaries beyond its original discovery site, a conservation outcome considered one of the notable success stories to come out of the original controversy.
What does a snail darter eat?
This species feeds primarily on small aquatic snails, a diet more specialised than many other darter species, which typically take a broader mix of small invertebrates, and it forages by picking snails directly off clean, gravelly or rocky river bottoms in flowing water.
What habitat does the snail darter need?
This species depends on clean, well-oxygenated river shoals with gravel or rocky bottoms and flowing water, a habitat type sensitive to sedimentation, pollution, and the still-water conditions created by dam impoundments, which is exactly the kind of habitat the proposed Tellico Dam threatened to eliminate at the original discovery site.