USFWS determined threatened species status under the ESA for the Big Creek crayfish (Faxonius peruncus) and the St. Francis River crayfish (Faxonius quadruncus), two crayfish species from southern Missouri. They also finalize a rule under the authority of section 4(d) of the Act that provides regulatory measures that are necessary and advisable to provide for the conservation of these species. In addition, they designate critical habitat for the species; in total, approximately 1,069 river miles (1,720 river kilometers) for the Big Creek crayfish and 1,043 river miles (1,679 river kilometers) for the St. Francis River crayfish in Iron, Madison, St. Francois, Washington, and Wayne Counties, Missouri, fall within the boundaries of the critical habitat designations. This rule applies the protections of the Act to these species and their designated critical habitats. This rule is effective 30 May 2023. POC is John Weber, Field Supervisor; USFWS; Missouri Ecological Services Field Office; 101 Park DeVille Drive, Suite A; Columbia, MO 65203–0057; tele: 573–234–2132. (Federal Register 27 April 2023 [Rule] Pages 25512-25542)