 However, many of the plant and animal species inhabiting the current Chautauqua Lake and Wildlife Refuge and adjacent Illinois River are nonnative and invasive species such as the Asian carp.As of 2005, of the 4,388 acres (17.8 km²) of the Chautauqua National Wildlife Refuge, 3,200 acres (12.9 km²) were classified as an open pool, 800 acres (3.2 km²) were classified as "water and timbered bottomland", and the remaining 388 acres (1.6 km²) were classified as upland forest.The closest numbered highway is U.S. Highway 136 in Mason County.