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Montana Field Guide

Montana Field Guides

Flathead Chub - Platygobio gracilis

Native Species

Global Rank: G5
State Rank: S5
(see State Rank Reason below)

Agency Status


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State Rank Reason (see State Rank above)
Currently ranked a S5 because it is common, widespread, and abundant (although it may be rare in parts of its range). Not vulnerable in most of its range.
General Description
The flathead chub has one of the greatest north-south distributions of any of the minnows. It extends from New Mexico to the northern Yukon Territory in Canada. Here in Montana it is found in the plains and foothill streams of our Missouri-Yellowstone River complex and is an indicator species of the Medium Warmwater River Fish Assemblage. Its most conspicuous features are a barbel or "whisker" at each corner of its mouth, flattened head and streamlined appearance. The sleek body shape and pointed fins are believed to be adaptations for living in fast water. Flathead chubs grow to about 12 inches in length and are sometimes used as bait. They are often caught by anglers.

Diagnostic Characteristics
Very silvery, shading to brown or dusky on back. Mouth large with a conspicuous barbel at each corner. Pectoral fin sickle shaped with long, sharply pointed tip that may extend almost to front of pelvic fin.

Species Range
Montana Range


Western Hemisphere Range


Range Comments
In Montana, the linear distance of streams and rivers occupied by the flathead chub is between 10,000-20,000 km (6,000-12,500 miles). Linear range was calculated to be a conservative 10,961 km (6850 river miles) of actual documented occupied streams to a more liberal river extent of >12,400 km (8,000 miles) based on MFISH river miles calculations associated with surveys, this was calculated for the Nature Serve Species ranking in 2012.

Observations in Montana Natural Heritage Program Database
Number of Observations: 1877

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Makes spawning run to lower Marias River.

Plains rivers and streams with some to moderate turbidity. Many reaches of prairie streams and rivers have the characteristic riffle/run/pool habitat and gravels preferred by flathead chubs. Studies on middle Missouri River showed it was relatively more abundant in the lower gradient downstream sections.

Food Habits
Eats mostly aquatic invertebrates of all sorts but includes some vegetation. Heavy seasonal use of terrestrial insects.

Were most common in main channel border and side channel chute. Habitat types on middle Missouri River. Commonly found in both riffles and pools.

Reproductive Characteristics
Sexually mature at 2 years. Probably spawns during July. Middle Missouri River study showed spawning from mid June to latter half of July with peak in early July.

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Citation for data on this website:
Flathead Chub — Platygobio gracilis.  Montana Field Guide.  .  Retrieved on , from