Flathead Chub

Platygobio gracilis

Flathead_Chub_Platygobio_gracilis_8-27-13.jpg

Flathead chub side view photo with black background
Flathead chub, Platygobio gracilis
Lance Merry
Endangered
Species of Conservation Concern
Family

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

Description

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.

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

Size

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.

Foods

The flathead chub 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. Today, it is nearly gone.

Status

State Endangered; a Species of Conservation Concern in Missouri.

Historically the flathead chub 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 extirpated from our state.

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 chubs 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, taking into account the many complex issues involved.

Ecosystem connections

Clearly, this species is adapted for unclear waters, and it 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 many catfish, which also use taste as the way to find food.