Fish play a complex role in the health of a river ecosystem such that a diverse mix of species is integral to a properly functioning system. Surveys of the region have found fish on several levels of the food web ranging from insectivores such as northern hog suckers, piscivores such as longnose gar, and detritivores such as central stoneroller. Fish are also important to mussel larvae, known as glochidia, since they require a fish host in order to attain maturity. Fish is an important food source for piscivorous birds, reptiles, and amphibians.

The Scioto River borders several of the park units and undoubtedly supplied the Hopewell with abundant fish for many meals. Based on surveys conducted by the Ohio Environmental Protection Agency, a total of 54 fish species have been collected from this stretch of the river. For fishing enthusiasts, the river is inhabited by smallmouth bass, sauger, and channel catfish. State-listed species can also be found, including the river redhorse, goldeye, and Tippecanoe darter.

Paint Creek, a tributary of the Scioto River, contains a total of 65 fish species along its mainstem and tributary, North Fork Paint Creek. This creek contains many similar species as the Scioto River, as well as some not found in the larger river. Some state-listed species include the river redhorse, eastern sand darter, and bluebreast darter. And the breeding colors of the rainbow darter, orangethroat darter, and variegate darter are quite a sight to see!