Gila Chub

DESCRIPTION:
Gila Chub have a thick, chunky body and a subterminal mouth. The scales are relatively thick, coarse, and overlap broadly and radiate out from the base. Body is dark, sometimes black, with a lighter belly speckled with gray and usually with diffuse lateral lines. Breeding males and to a lesser extent, breeding females develop red to orange on the lower parts of the head and body especially on the bases of the pectoral, pelvic, and anal fins. The fins are small and often darkly pigmented, and the margins are usually rounded (sometimes square rarely convex). Dorsal rays number 8 or fewer anal rays 8, and pelvic rays 7-8.

DISTRIBUTION & STATUS:
Historically, Gila Chub inhabited approximately 43 rivers, streams, and spring-fed tributaries throughout the Gila River basin in southwestern New Mexico, central and southeastern Arizona, and northern Sonora, Mexico.

Gila Chub is currently restricted to the Gila River Basin in Arizona (AZ), New Mexico (NM), and Sonora occupying a highly fragmented range further reduced by water developments and impacts of other non-native species. NM specimens have not been sufficiently examined to pinpoint the species distribution there but was recorded in the past from Apache Creek, Duck Creek, and San Simone Cienega just west of the NM line in the San Francisco Basin and is likely in Turkey Creek, NM. Gila Chub persisted in Mexico in the Rio San Pedro drainage and may survive with other Gila River Basin fishes in the southern loop of the upper Rio Santa Cruz that enters Sonora from AZ, then loops back northward into AZ, where it was last recorded in 1996. The primary threats facing the Gila Chub are predation by and competition with non-native fish and bullfrog species as well as crayfish; disease; and habitat destruction and fragmentation due to water diversion, dredging, recreation, roads and livestock grazing. Gila Chub was listed as endangered in 1994 and in 2002 approximately 85 to 90 percent of the Gila Chub's habitat had been degraded or destroyed.

HABITAT:
Gila Chub is found in well-developed pools in small to middle-sized head water creeks, becoming most common in marshy areas, cutoff pools, or holes undercut in erosive reaches. They are also found in isolated, flood-excavated pools maintained by underflow in intermittent reaches. Fixed channel configurations by canyon walls or instream obstructions promote scour, assuring excavation of depressions that act as permanent pools when substrate percolation through coarse alluvium (rises to fill them. Undercut banks, deep scoured places near obstruction, or cover from woody debris ( ex-large tree branch).

FOOD HABITS:
Gila Chub stomach contents included detritus (dead particulate organic material,), algae – and diatoms, aquatic and terrestrial insects, and fishes. Terrestrial insects include mostly ants with few caterpillars and beetles. Gravel indicated benthic (occurring at the bottom of a body of water) foraging and feeding usually takes place at night or in the late evening.

REPRODUCTION:
Gila Chub matures during the second to third year of life. Young are active throughout the day, while larger individuals tend to be most active in the evening and early morning. Reproduction primarily occurs in the late spring and into summer. Spawning may occur over beds of submerged aquatic vegetation. In relatively constant spring-fed ponds, reproduction may last throughout late winter, spring, and summer — and even autumn.