The Fish and Wildlife Service (Service) determines five freshwater mussels, the fat threeridge (Amblema neislerii), shinyrayed pocketbook (Lampsilis subangulata), Gulf moccasinshell (Medionidus penicillatus), Ochlockonee moccasinshell (Medionidus simpsonianus), and oval pigtoe (Pleurobema pyriforme) to be endangered species, and two freshwater mussels, the Chipola slabshell (Elliptio chipolaensis) and purple bankclimber (Elliptoideus sloatianus) to be threatened species under the Endangered Species Act of 1973, as amended (Act). These mussels are endemic to eastern Gulf Slope streams draining the Apalachicolan Region of southeast Alabama, southwest Georgia, and north Florida. Their center of distribution is the Apalachicola- Chattahoochee-Flint (ACF) River basin of southeast Alabama, southwest Georgia, and northwest Florida, and the Ochlockonee River system of southwest Georgia and northwest Florida. They are currently known from restricted portions of from one to four independent river systems. These species inhabit stable sandy and gravelly substrates in medium- sized streams to large rivers, often in areas swept free of silt by the current. The abundance and distribution of the seven mussel species decreased historically from habitat loss associated with reservoir construction, channel construction and maintenance, and erosion. These habitat changes have resulted in significant extirpations (localized loss of populations), restricted and fragmented distributions, and poor recruitment of young.