KNOXVILLE, Tenn.— The U.S. Fish and Wildlife Service announced a proposed rule today to protect 104 miles of rivers as critical habitat in Tennessee and Virginia for a fish called the sickle darter under the Endangered Species Act. The Service designated the sickle darter as a threatened species in November.

The sickle darter was protected following a 2010 petition filed by the Center for Biological Diversity and a 2015 agreement with the agency to protect the fish.

“Critical habitat is essential for this beautiful bronze fish and the rivers it calls home,” said Will Harlan, a scientist at the Center. “Protecting these 104 miles is an important step toward restoring not only the sickle darter but the health of Appalachian rivers.”

The sickle darter used to be found in rivers across southern Appalachia. Today only six populations remain, living in southern Virginia and eastern Tennessee.

The proposed critical habitat protects 16 miles of the Little River, 30 miles of the Emory River, 14 miles of Copper Creek, 25 miles of the North Fork of the Holston River, 14 miles of the Middle Fork of the Holston River, and five miles of the Sequatchie River.

“It’s disappointing that the designation doesn’t include portions of the French Broad River watershed so the species can fully recover,” said Harlan. “The sickle darter once thrived in the French Broad River and other rivers in North Carolina’s Blue Ridge region.”

Critical habitat is key to an endangered species’ survival. Species with designated critical habitat are twice as likely to be recovering as species without it.

The primary threats to the sickle darter are siltation, water pollution and dams. Siltation from logging and development fills the spaces between rocks on the river bottom that the fish needs to lay eggs and find prey. The sickle darter’s water is also polluted by animal waste, domestic sewage, pesticides, and heavy metals from mining. Dams have isolated sickle darter populations and limited their movement.

“When we protect the sickle darter’s future, we’re also safeguarding our own,” said Harlan. “People need healthy water and healthy rivers, just like the animals who live in them.”

The sickle darter is one of the largest darters, growing to be nearly five inches long with a prominent black side stripe, and can live up to four years. It uses its large mouth and pointed snout to feed on larval mayflies, midges, riffle beetles, caddisflies and dragonflies. Its scientific name is Percina williamsi, honoring renowned biologist Jim Williams who has been working to describe and protect freshwater species from the southeastern United States for more than half a century.