The bonytail chub is native to the Colorado River drainage. Originally abundant throughout basin, it has declined to the point it is now endangered and is the rarest of the endemic big-river fishes of the Colorado River system. No young individuals have been captured in recent years and it has been called functionally extinct. In order to preserve the species biologists captured adults from Lake Mohave from 1976 to 1989. Their young, the hatchery fish, and maybe a few adults in the wild, are the entire known population of bonytails. While little is known about this chub, it is believed they prefer backwaters with rocky or muddy bottoms and flowing pools, rather than swift currents.
This large chub can reach 24 inches in length and is typically green-gray on top, with whitish undersides. During spawn male’s paired fins and belly turn reddish-orange. Their fins are large coupled with a streamlined body that is very thin at the tail. They are long-lived, with specimens aged at 50 years.
Bonytails spawn in the spring and summer over gravel bottoms. The eggs are broadcast over the bottom and there isn’t any parental care. Females produce up to 17,000 eggs that hatch in about nine hours after fertilization. They are thought to sexually mature in 2 to 3 years.
While little is known of chubs feeding habits, adults are thought to feed mostly on small fish, algae, plant debris, and terrestrial insects.
Bonytail Chub in Colorado
Courtesy of Natural Diversity Information Source species profile.
Habitat: Little is known about this species. The bonytail prefers eddies and pools, not swift currents (Vanicek and Kramer 1969).
Description: A highly streamlined fish; concave skull arching into a nuchal hump predorsally; caudal peduncle pencillike, long and slender; snout does not overhang upper lip; scales often minute or absent from chest, stomach and caudal peduncle; fins falcate with 10 dorsal fin rays, and 1011 anal fin rays; in young, less than 5.9 inches, eye diameter greater than 2/3 caudal peduncle depth. Adults are dark on top, light below. Often they are very dark in clear waters and pale in turbid waters. Fins are dusky with yellow pigment near base (Minckley 1973). Adults (7 years of age) can be 14 inches long and weigh more than one pound (Vanicek and Kramer 1969).
Range in Colorado: Found historically throughout the Colorado River Drainage, in recent years bonytail have only been taken from the Green River in Utah and lakes Havasu and Mohave (Miller, et al. 1982). Jordan (1891) reported one bonytail from the Gunnison River near Delta and other specimens have been taken in the Green River in Colorado. No bonytails had been collected in Colorado for several years until 1984, when one individual was collected at the Black Rock area of the Colorado River west of Grand Junction, Colorado, (L. Keading, personal communication). The bonytail is listed as a federal and state endangered species.
Status: Federally Endangered, State Endangered
The taking of Bonytail Chub for any purpose is prohibited.