Roundtail Chub

DESCRIPTION:
Roundtail Chub has a streamlined, moderately slim body. Based on the population means the caudal peduncle length divided by its depth is greater than 2.3 and the head length is divided by the caudal peduncle depth is greater than 3.25. Scales are thin and overlap narrowly, have weal or no basal radii, and typically number 75 to 90 (usually more than 78:extremes 71 and 99) in the lateral line. There are 9 (rarely 8 or 10) dorsal and anal fin rays, and usually 9 pelvic fin rays. Body color is silvery, darker above and lighter below; lateral blotching is common in adults from the Verde River system, otherwise rare. Breeding males, and to a lesser extent females, develop orange to red on the lower parts of the head, lower sides and belly, and fin bases. Both sexes also develop small breeding tubercles, more extensive in males than in females.

DISTRIBUTION & STATUS:
Roundtail Chub are endemic to the Colorado River Basin, California, Colorado, Nevada, New Mexico, Utah, and Wyoming including the Bill Williams and Gila river systems of Arizona and New Mexico, and onto the delta in Baja California and Sonora. In New Mexico, the historic range of Roundtail Chub included the San Juan River and its tributaries, the Zuni River (a Little Colorado River tributary), and the Gila and San Francisco rivers. Within their ranges, this species moved freely among the larger, interconnected rivers, but has now disappeared from many. Today the range of Roundtail Chub has been reduced to several basins within Arizona and New Mexico; Apache, Coconino, Gila, Graham, Greenlee, La Paz, Maricopa, Mohave, Navajo, Pinal, Yavapai, Catron (NM), and Grant (NM). In the Gila River drainage of New Mexico, Roundtail Chub are limited mainly to the upper East Fork Gila River, the lower Middle Fork River, and lowermost West Fork Gila River. They are threatened by water development, pervasive predatory and competitive non-native fishes. In other areas, smaller headwater tributaries, livestock grazing is a common threat. Livestock reduces cover for Roundtail Chub (adults, juveniles, young-of-year) by flattening the stream banks and consumption of most, if not all, the riparian vegetation. The federal status of this species is not listed. However in Arizona it is a designated species of special concern, in New Mexico it is endangered, and in Mexico they are listed as threatened.

HABITAT:
Roundtail Chub is secretive and is often found in pools and is locally abundant in channels of large rivers or in association with cover such as boulders or overhanging cliffs, cut banks, or vegetation in smaller streams. They are most commonly found in pools with cover (boulders, uprooted trees, and undercut banks) having depths of 2 m or more with sand and gravel substrates. Juveniles are occasionally found in shallower and faster velocity water then adults; such areas typically are along undercut stream banks with overhanging vegetation. In Arizona rivers, the fish tend to occupy pools and eddies, often concentrating in relatively swift, swirling waters below rapids, and moving into smoothly-flowing chutes in small groups.

FOOD HABITS:
Roundtail Chub are omnivores, consuming a wide variety of aquatic and terrestrial invertebrates, aquatic plants, and detritus. They appear to be rather opportunistic and sporadic in its feeding habits, taking fish, aquatic insects, and terrestrial insects. Midge larvae and mayfly nymphs were the most abundant food items in the smaller fish, whereas adults consumed a greater diversity of food items, including aquatic and terrestrial insects. Young-of-year move into quiet backwaters until 25 to 50 mm long, where they feed on
small insects, crustaceans, and algal films.

REPRODUCTION:
Roundtail Chub reproduce in spring and early summer in pool habitats, often in association with beds of submerged vegetation or other kinds of cover such as fallen trees and brush. They have been observed broadcast spawning in deeper pools or in riffles upstream of pools with loose rocks or gravel beds. Typically there is one female and multiple male "escorts". Females do not spawn until Age 3 but males have been recorded spawning as early as Age 2.