On January 24, 2023, the U.S. Fish and Wildlife Service (Service) proposed to designate approximately 104 river miles as critical habitat for the sickle darter (Percina williamsi) under the Endangered Species Act (ESA). The critical habitat designation would be divided into six areas—Little River, Emory River and Rock Creek, Copper Creek, North Fork Holston River, Middle Fork Holston River, and Sequatchie River—which together span Bledsoe, Blount, Morgan, and Roane Counties in Tennessee, and Scott, Smyth, and Washington Counties in Virginia. Nearly 80 percent of the critical habitat proposed for the sickle darter is already designated as critical habitat for other federally listed species.

The sickle darter is larger than most darters, and can grow to be about five inches long. It is recognizable by a sickle-shaped bar below its eye and a small black bar extending below a black spot at the base of its tail. This darter typically occurs in slow-flowing pools of larger, upland creeks and small to medium rivers, and prefers habitat featuring clean sand or gravel substrates, stands of American water willow, or piles of woody debris. It spends most of its time in the water column, hovering slightly above the stream or river bottom. Because the species has been affected by the construction of reservoirs and other water impoundments, the sickle darter is now found in only six of the nine tributary systems that comprised its original historical range.

Designation of critical habitat for this species has been expected for over two years. The Service issued a proposed rule on November 12, 2020 to list the sickle darter as a threatened species with an accompanying ESA section 4(d) rule. Though the listing of the sickle darter was finalized on November 8, 2022, the Service was delayed in determining critical habitat because it was still in the process of obtaining information about the impacts of the listing designation. After reviewing all relevant information, the Service concluded in its January 2023 proposed rule that designating areas of critical habitat is now finally both prudent and determinable.

The Federal Register notice states that the proposed rule will be open for comments until March 27, 2023. The Federal Register notice and supporting documents are available at regulations.gov, under Docket Number FWS-R4-ES-2022-0098.