Blue Chub

The blue chub has its dorsal fin supported by 9 soft rays while the anal fin contains 8 or 9 soft rays. It has a large eye, a pointed snout with a terminal mouth which extends as far as the front of the eye. It has a rather slender, laterally compressed body with a slender caudal peduncle. They have silvery sides with a dark back. The males develop a blue snout, orange fins and orange flanks in the breeding season. They rarely exceed 38 cm (15 in) in length, with a maximum total length of 41 cm (16 in).

The blue chub is endemic to the Western United States where it is found in the Lost River and the Klamath River in California and Oregon. It has colonised reservoirs downstream of Klamath Falls where it was not thought to be present in the past. It has also been introduced to other river catchments in Oregon. This species prefers rocky habitats in pools of small streams to large rivers and along the rocky shores of reservoirs and lakes.

The blue chub is classified in the genus Gila, a genus proposed in 1853 by Spencer Fullerton Baird and Charles Frédéric Girard. Baird and Girard did not explain what the name alluded to, it may be to the Gila River, although Baird and Girard said the first three species they classified in this genus were found in the neighbouring Zuni River, which they may have thought were both part of the same drainage. Alternatively, they chose the name to give the genus a southwestern United States flavor. The specific name, coerulea is an alternative spelling of caerulea, which means "dark blue". Girard described this species as having a grayish blue back.