Northern studfish have a light brown back with a short gold streak down the center of their back just in front of the dorsal fin. The dorsal and anal fins are set far back on the body like other topminnows. Their sides are silver or blue in color with reddish brown spots on the sides of their head and many reddish brown horizontal lines along their sides. On breeding males these lines and spots are a brilliant red over a vivid light blue background. Breeding males also have a bright orange margin to their tail followed by an almost black band.
Habitat and Habits
Northern studfish are found along the edge of pools and riffles in a wide size range of streams. They tend to stay in shallow water often only a couple of inches deep, preferring clear waters with clean sand and gravel substrates. Northern studfish spawn in shallow water along the edge of streams. Unlike most topminnow species, they spawn on clean gravel substrate rather than plants. It has been reported that they may occasionally use the nests of longear or other sunfish species as spawning sites. No parental care is given to the eggs or young. (Brian Zimmerman, ODNR Division of Wildlife)
Northern studfish are native to the southern portion of the gulf drainage (the shallow, gravelly stream margins along tributaries of the Mississippi), but have been encroaching into Ohio and Iowa, probably as a result of illegal releases of aquarium pets. Where they occur outside of their native range, northern studfish may displace native topminnows.