The sturgeon chub is a slender minnow with small eyes, a long, fleshy snout, and a small, horizontal mouth. Many of the scales on the back and sides have a low ridge or keel — a unique characteristic for this minnow. The mouth has a small, conical barbel at each corner. The snout is long and flattened, projecting far beyond the upper lip. The eye diameter is much less than the length of the snout (the distance from the front edge of the eye to the tip of snout). The front of the dorsal fin is closer to the tip of the snout than to the base of the tail fin.
This fish is light brown on the back, thickly dusted with fine dark specks; the sides are silvery without definite markings. The belly is silvery white. The lower lobe of the tail fin is darker than the upper lobe. Males in breeding condition have small tubercles along the rays of the pectoral fins.
Length: adults are typically 1¾ to 2½ inches, with a maximum of about 3 inches.
Occurs in the Missouri River and in the Mississippi River downstream from the Missouri’s mouth. It does not typically enter tributary streams, nor does it ascend the Mississippi above the mouth of the Missouri.
Habitat and Conservation
The sturgeon chub is confined to the open channels of large rivers, where it lives in a strong current over a bottom of sand and fine gravel. The construction of several large reservoirs upstream from Missouri have eliminated much of this fish’s habitat, since these dams and lakes function as huge sediment traps, arresting the river’s current and causing silt to fall to the bottom behind the dam. Downstream of the dams, however, the river bottom has become less muddy, and the amount of gravel bottom has increased, thus sturgeon chub mainly occur in Missouri’s section of the river.
This small, little-known minnow is beautifully adapted for life in muddy, murky water, where vision is of little value and the sense of smell is the best way of locating food, with its small eyes and plentiful external taste buds on the head, body, and fins. It navigates well in swift waters thanks to its streamlined body shape, deeply forked tail, and keeled scales.
Food
Sturgeon chub feed on bottom-dwelling immature insects such as midge larvae and other small aquatic insects and crustaceans. To forage, the fish swims slowly along the bottom of the channel, dragging its large pectoral fins and barbels along the substrate. Taste buds on these parts and the head aid them in detecting food. Large amounts of sand and other sediment are taken into the mouth along with food items; the food is swallowed, and the sand is ejected from the mouth and gill openings.
Status
A species of conservation concern in Missouri; classified as vulnerable in our state.
Life Cycle
Sturgeon chub can live up to 4 years, but a lifespan of 2 years is more common. They spawn from May through August. Fertilized eggs are slightly heavier than water and must drift in the river current for several days as they develop. Dams fragment this fish’s habitat in detrimental ways: eggs that drift into a river impoundment, where the current is arrested, will not survive. Sturgeon chub occasionally hybridize with the speckled chub, M. aestivalis.
Human Connections
The Missouri River upstream from our state is impounded by six major dams. People constructed those dams in order to control the river for our own purposes, but the dams and impoundments have eliminated almost half of this fish’s former range. Missouri’s portion of the Missouri River is free-flowing, and thus our state holds some of the best remaining habitat for sturgeon chub.
Ecosystem Connections
The open river channels where sturgeon chub live are sparsely populated by other small fish, except for speckled chub, sicklefin chub, and flathead chub. These river chubs are important food for sturgeon species, including the federally endangered pallid sturgeon that lives in our rivers.
This species’ common name comes from the resemblance of its head to that of a sturgeon. Both the sturgeon chub and sturgeon face similar environmental challenges, and both have rather similar foraging strategies, so even though they are very unrelated, it is little surprise they should look similar.
