Flathead Chub

Platygobio gracilis


Color illustration of Flathead Chub
Joseph R. Tomelleri. Used with permission.
Species of Conservation Concern

Cyprinidae (minnows) in the order Cypriniformes (carps, minnows and loaches)


A slender, silvery minnow with small eyes, a large, slightly oblique mouth and sickle-shaped, pointed, pectoral fins. Head distinctively wedge-shaped in profile. Mouth with a small barbel at corner. Snout flattened and rather pointed, projecting slightly beyond upper lip.

Back light brown; sides and belly silvery-white without definite markings. Lower lobe of tail fin darker than upper lobe. Breeding males without special colors, but with very small tubercles on upper surface of head and body and along some rays of all fins except tail fin.


Adult length: about 3½ to 7½ inches; maximum about 9½ inches.

Habitat and conservation

In big rivers, this species prefers the continuously turbid waters where the current is swift and the bottom composed of sand and fine gravel. But where it occurred in tributaries in northwestern Missouri, it lived in pools of small creeks with clear water, little current, with coarse gravel and bedrock bottoms. These might represent different subspecies of flathead chubs.


The flathead chub is apparently depends largely on external taste buds and to a lesser extent on sight to find its food. The diet consists mostly of terrestrial insects that fall into the water, along with lesser quantities of small invertebrates and plant material. In the past, before upstream damming, the murky Missouri River offered little competition for this feeding niche. Today the river is much clearer and the flathead chub is outcompeted by visual feeders such as the emerald shiner.

image of Flathead Chub distribution map
Distribution in Missouri

Historically inhabited the entire Missouri River, and some of its tributaries, and the Mississippi River between the Missouri’s mouth and the Arkansas line. In the 1940s, it made up 31 percent of all small fishes in the Missouri. By the 1980s, it was only 1.1 percent. Today, it is nearly gone.


State Endangered; a Species of Conservation Concern in Missouri. The rapid, fifty-year decline of this species coincided with the construction of a system of six large reservoirs on the Missouri River upstream of the state. The dams changed the flow and altered the bed load and turbidity (muddiness) of the water. The flathead chub is adapted for finding food in muddy water, where sight-feeding fish have trouble. With clearer water, sight-feeders outcompete the chubs for food.

Life cycle

Details of this fish’s spawning habits are unknown, but in Missouri the fish is thought to spawn in July or August. It is believed that flathead chub live for at least 3 or 4 years.

Human connections

When humans alter a landscape, it always effects plants and animals. There are complex issues involved in the decision to dam a river, and a great many interests at stake. Biologists can point out the effects on nature, but in a democracy, it is up to the voters to make informed, wise choices.

Ecosystem connections

Clearly, this species is adapted for unclear waters, and is an example of how the demands of a particular environment—the Muddy Missouri—have formed a fish capable of thriving in it. Other fish adapted for murky river conditions are catfish, which also use taste as the way to find food.