Roundtail Chub, Gila robusta
Note: This Species is currently considered to be VULNERABLE and if encountered should be handled accordingly.
Roundtail Chub, Gila robusta. Fish caught from El Rito Creek, Santa Rosa, New Mexico, August 2020, quickly photographed in an aquarium type setting and quickly returned to its native environment unharmed. Length: 12.8 cm (5.0 inches).
Roundtail Chub, Gila robusta. Fish caught from Fossil Creek, Camp Verde Arizona, April 2015. Length: 26 cm (10 inches). Catch, photograph, and identification courtesy of Chris Moore, Peoria, Arizona.
Roundtail Chub, Gila robusta. Fish caught from the Verde River, Camp Verde, Arizona, November 2015. Length: 28 cm (11 inches). Catch, photograph, and identification courtesy of Chris Moore, Peoria, Arizona.
Roundtail Chub, Gila robusta. Fish caught from the Verde River, Camp Verde, Arizona, November 2015. Length: 28 cm (11 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
Goundtail Chub, Gila robusta, Breeding Male. Fish caught from the Verde River, Camp Verde, Arizona, November 2015. Length: 28 cm (11 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
The Roundtail Chub, Gila robusta, is a member of the Carp and Minnow or Cyprinidae Family, and is known in Mexico as carpa cola redonda. Globally, there are twenty-one species in the Gila Genus, of which eleven are found in Mexico’s freshwater systems. The Gila Genus is considered to be one of the most fascinating and important fish groups to taxonomists.
The Roundtail Chub is a large minnow that has a deep compressed body with a humped back being slightly deeper anterior to the dorsal fin and tapering to the caudal fin. Their head is flat to slightly concave and their caudal peduncle is slender. They are a dark olive-gray color dorsally that transitions to silvery on the sides. Their lower lip is black. Breeding males develop red or orange colors on the lower half of their cheeks and pectoral and pelvic fin bases. Their head has an overhanging snout and a relatively large terminal mouth that extends to the front of the eyes. Their anal fin has 9 rays; their caudal fin is large and forked; and, their dorsal fin has 9 rays. They have at least 10 gill rakers on the lower arch.
The Rountail Chub is native to high desert freshwater rivers and streams with low to moderate gradient that are found in open areas without cover in both deep water and shallow water pools below riffles, rapids and waterfalls over cobble-rubble, sand-cobble or sand-gravel substrate. During periods of drought, they are forced out of the deeper streams into shallower pools. They have a strong tenacity, capable of maintaining populations in small habitats under severe environmental conditions. They are subject to die-offs in waters in excess of 30.5oC (87oC). They reach a maximum of 43 cm (17 inches) in length. The Roundtail Chub is a voracious predator that consumes large amounts of crayfish, fish, frogs and both aquatic and terrestrial insects. They rely on their cryptic coloration for camouflage to avoid predation but are known to be heavily preyed upon numerous non-native introduced species. Reproduction is polygynandrous (promiscuous) and oviparous with substantial spawning migrations with external fertilization that involves annual breeding cycles commencing in the spring when water temperatures reach 18oC (64oF). The females deposit eggs over clean gravel or cobble substrate at depths over 25 m (82 feet) in the larger pools and bury their eggs to protect them from predation. They have life-spans of up to twenty years.
The Roundtail Chub is found in the fresh water streams and rivers of northwest Mexico in Sonora and Sinaloa including the Rio Yaqui River south to Rio Piaxtla. In the United States their populations are limited to Southern Arizona and they are considered to be endangered with extensive on-going efforts to recover their populations.
The Roundtail Chub is very similar to several chubs that are subject to extensive study as they different populations that have independent evolutionary paths that vary by location and formerly accounted as several species which have recently been reclassified as four subspecies. They are also known to hybridize with Gila cypha. They can be found in warmer waters and easily separated from trout as they lack an adipose fin.
From a conservation perspective the Roundtail Chub is currently considered to be VULNERABLE due to their very limited range and the ongoing destruction of their native habitats especially in arid years. Their populations and ranges are in significant decline and their long-term viability is threatened by water pollution, stream flow depletion, siltation from human activities, and predation by introduced fishes including Channel Catfish, Flathead Catfish, Smallmouth Bass, Brown Trout and Rainbow Trout. In Southern Arizona their long-term survival is of interest to many and numerous efforts are on-going for preservation and reestablishment of native populations. They are scientifically interesting due to their survival skills and taxonomy. In some regions they are considered to be a targeted game fish and heavily pursued by recreational anglers.