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mooneye (Hiodon tergisus) Photo © Uland Thomas

Features and Behaviors

The body is compressed laterally giving a thin appearance. The upper body is a shiny, light green while the sides and belly are silver. The eye is large. The base of the dorsal fin is in front of the base of the anal fin. A lateral line is present. This species averages about nine to 11 inches long as an adult. There is a fleshy keel on the belly, but there is no jagged row of scales in in the belly’s midline. The fleshy keel is found between the vent and the base of the pelvic fins. There are no scales on the head and no spines in the fins. An adipose eyelid is present. The pelvic fins are abdominal. Teeth are present on the jaws, and the dorsal fin has 11 to 12 main rays.

This species spawns early in spring. Its eggs float and can be dispersed by water currents. Mooneyes eat aquatic insects, other invertebrates and small fishes.

Illinois Range


Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Hiodontiformes
Family: Hiodontidae

Illinois Status: common, native