Mooneye distribution is limited to the large river drainages across the state. The species is commonly found in the Mississippi and Missouri rivers, and in a number of the larger interior streams, such as the Des Moines River. Populations are concentrated more along the southern and eastern borders of the state, where it is occasional to common in abundance.

Mooneyes have deep bodies that are strongly compressed laterally. Color varies from steel blue on the back to silver sides and a white belly. The eye has a silvery iris. The belly has a fleshy keel but lacks scutes. The head is blunt and rounded with a slightly oblique mouth. Teeth occur in both jaws as well as on the roof of the mouth and on the tongue. There are 15 to 17 gill rakers along the lower limb of the first gill arch. The fish has adipose eyelids. Scales are cycloid and the lateral line contains 52 to 57 scales. The dorsal fin has 10 to 14 rays and inserts forward of the anal fin, which has 26 to 29 rays. Males have a sickle-shaped anal fin, and in females it is concave. An axillary process is found near the base of the pelvic fin.

Mooneye prefer swift, clean water and will not tolerate silted conditions. Little is known of the spawning ritual of this fish, but it probably occurs at random in April and May in shallow areas of cleaner streams. Each female produces about 10,000 to 20,000 eggs, and no care is given to the young. Mooneye commonly reach 9 to 11 inches in length, with a maximum size of about 10 to 12 inches. Food consists mostly of plankton during the young stages of life, but the fish switch quickly to insects, mollusks, crayfish and small fish at later stages.

*Mayhew, J. (editor). 1987. Iowa Fish and Fishing. Iowa Department of Natural Resources, Des Moines, Iowa. 323 pp.