Fish species in the Bill Williams river include largemouth bass, yellow bullhead, green sunfish, bluegill, carp, mosquitofish, red shiner, razorback sucker, and others. The lowland leopard frog, North American river otter, beaver, muskrat, Arizona toad, and spiny-spotted turtle are among the major aquatic vertebrates found in or near the water. Plants in the riparian zones include several kinds of willows as well as bulrushes, and saltcedar. The Bill Williams Wildlife Refuge near Parker is frequented by at least 335 species of birds.