The Potomac River and its tributary streams within the George Washington Memorial Parkway (GWMP) are home to at least 61 species of fish (and one hybrid). Mine Run in Great Falls Park has the highest species richness of any stream in GWMP with 22 species recorded. Within GWMP, the Fallfish (Semotilus corporalis) and Longear Sunfish (Lepomis megalotis) are found only in Mine Run, the Swallowtail Shiner (Notropis procne), Fantail Darter (Etheostoma flabellare), Potomac Sculpin (Cottus girardi), and the Satinfin Shiner (Cyprinella analostana) are restricted to Turkey Run, and the Northern Hogsucker (Hypentelium nigricans) and Margined Madtom (Noturus insignis) are found only in Difficult Run. While on the Maryland side of GWMP the Sea Lamprey (Petromyzon marinus), Golden Redhorse (Moxostoma erythrurum) and Greenside Darter (Etheostoma blennioides) are known to occur only in Cabin John Creek. The American Eel (Anguilla rostrata) is found in more GWMP streams than any other species. Dyke Marsh, located along the Potomac River, is home to at least 38 species.