The French Creek Watershed contains 27 of Pennsylvania’s approximately 65 species of freshwater mussels, the most diverse population of any stream in the state, and any stream further north and east in the nation. Four of these, the Northern Riffleshell (Epioblasma torulosa rangiana), Rayed Bean (Villosa fabalis), Snuffbox (Epioblasma triquerta) and Clubshell (Pleurobema clava), are classified as federally endangered in North America, and ten others are endangered in Pennsylvania. Mussels require clean, oxygen-rich water to filter food and absorb dissolved oxygen. In the microscopic larval stage mussels often attach to the gills of fish such as darters and are transported to different sites on the stream. As a result, their distribution and numbers are directly linked to the survival of these host fish.