Gila Chub, Gila intermedia
Note: This Species is currently considered to be ENDANGERED and if encountered should be handled accordingly.
Gila Chub, Gila intermedia. Accidental catch from a small stream in Arizona, September 2020. Length: 8.9 cm (3.5 inches). Fish was immediately photographed and quickly returned unharmed to its native environment.
The Gila Chub, Gila intermedia, is a member of the Carp and Minnow or Cyprinidae Family, and is known in Mexico as chirality del Gila. Globally, there are twenty-one species in the Gila Genus, of which eleven are found in Mexico’s freshwater systems.
The Gila Chub is a mid-sized-finned minnow with a deep chubby compressed body. They are a dark olive gray dorsally transitioning to silver ventrally with their scales having dark margins. While breeding their eyes become yellow-orange and the females develop a soft, fat, broad hump on the nape of their necks and the males develop distinct intense coloration with red and orange and the lower cheeks, rear portion of the lips and on their fins. The females are approximately 40% larger than the males. They reach a maximum length of 38 cm (15 inches) with the females being approximately 40% larger than the males. Their anal fin has 8 rays, their caudal fin is large and deeply forked and their dorsal fin has 8 rays. They have less than 10 gill rakers on the first arch. They are covered with large thick scales.
The Gila Chub is highly secretive freshwater species with the adults preferring deeper, quieter waters in pools and eddies below riffles or runs, often remaining in cover from terrestrial vegetation, boulders, and fallen logs at elevations between 600 m (1,970 feet) and 1,700 m (5,600 feet). The juveniles are found within the shallow margins of pools with aquatic vegetation or debris for cover. Older juveniles may reside in higher velocity runs and riffles. They are normally found mixed in with Desert Suckers, Gila Topminnows, Longfin and Speckled Dace, and Sonora Suckers. They are omnivores that consume algae, small fishes, aquatic insects, and terrestrial insects. They rely on their cryptic coloration for camouflage to avoid predation. Reproduction is polygynandrous (promiscuous) and oviparous with external fertilization that involves annual breeding cycles commencing in the spring. The females deposit eggs in the larger pools and bury their eggs to protect them from predation. The Gila Chub, in general, is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
In Mexico the Gila Chub has a vary limited distribution being limited to the Santa Cruz River system in Sonora.
The Gila Chub is a straight forward identification and cannot be easily confused with any other species.
The Gila Chub is a freshwater species that is endemic to the Gila River drainage in Arizona and the Santa Cruz River system in Sonora. They are found within the smaller headwater steams, springs, and marshes. The adults reside in deep water pools and the juveniles are found in riffles, pools and under banks. They frequent heavily vegetated areas that the utilize for protection and for foraging.
From a conservation perspective the Gila Chub is currently considered to be ENDANGERED, residing within critical habitat. With their native habitats undergoing human development which includes water diversion, elimination of aquatic habitats, removal of beavers that create dams that generate deep pools, the introduction of non-native predatory fishes (Green Sunfish, Lepomis cyanellus) and Largemouth Bass (Micropterus salmoides), and bullfrog and crayfish predation.