NMFS, designate and authorize the release of nonessential experimental populations (NEPs or experimental populations) of Sacramento River (SR) winter-run Chinook salmon (Oncorhynchus tshawytscha) and Central Valley (CV) spring-run Chinook salmon (O. tshawytscha) in the McCloud and Upper Sacramento Rivers upstream of Shasta Dam (the NEP Area), California, and, under the ESA, establish a limited set of take exceptions for the experimental populations. Successful reintroduction of populations within the species' historical ranges will contribute to viability and further conservation of these species. The issuance of limited protective regulations for the conservation of these species will provide assurances regarding the regulatory provisions of the ESA as they apply to SR winter-run and CV spring-run Chinook salmon to the people in the Upper Sacramento River and McCloud River watersheds. This final rule also announces the availability of a final environmental assessment (EA) that analyzed the environmental impacts of promulgating the experimental population rule and associated take exceptions. The final rule is effective 27 September 2023. POC is Steve Edmondson, steve.edmondson@noaa.gov or by phone at (916) 930–3600, or by mail at National Marine Fisheries Service, 650 Capitol Mall, Suite 5–100, Sacramento, CA 95814. (Federal Register 28 August 2023 [Rule] Pages 58511-58521)