Roundtail chub

Roundtail chub Gila robusta
Conservation status
Vulnerable  (IUCN 2.3)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Cypriniformes
Family:	Cyprinidae
Genus:	Gila
Species:	G. robusta
Binomial name
Gila robusta S. F. Baird & Girard, 1853

The roundtail chub, Gila robusta, is a cyprinid fish in the Gila genus, of southwestern North America. It is native to the Colorado River drainage basin, including the Gila River and other tributaries, and in several other rivers. It is part of the “robusta complex”, which includes the Gila robusta robusta, G.r. grahami, and G.r. seminuda.

Description

The body of Gila robusta is significantly larger forward of the dorsal fin, and posteriorly it is tapered towards the tail. The forehead area is concave. The mouth is largish, but does not reach as far as the pupil of the eye, and is overhung by the snout. The tail is deeply forked. Color is a grayish brown above, and a lighter shade below. Mature males sometimes acquire red-orange lower cheeks and paired fins during breeding season. Roundtail chub can reach almost to about 49 cm (19 in), but usually only grow to about 25–30 cm (10–12 in). Recently, it has been recorded at up to 43 cm in length.
Roundtail chub are also described to be “trout-like” because they possess a large mouth with the lower lip outlined in black. However, they lack the adipose fins on trout species.

Range

The range of Gila robusta is within the Colorado River drainage basin, found from the headwaters down to the mouth, in Utah, Colorado, Arizona, Nevada, and California, and northwest Mexico; as well as in other rivers of northwestern Mexico.

This species is rather variable, and formerly accounted as several species, until intermediate forms were discovered. Recognized subspecies include:

• Gila robusta grahami
• Gila robusta jordani - small streams along the White River (Nevada)
• Gila robusta robusta - small rivers
• Gila robusta seminuda

The roundtail chub has been extirpated from the Zuni and San Francisco Rivers of New Mexico.

In Arizona, specifically in Gila, Mohave, and Yavapai Counties, the roundtail chub occupies several tributaries: Fossil Creek, Oak Creek, Burro Creek, Francis Creek, Big Sandy River, Santa Maria River, Boulder Creek, Trout Creek, Sycamore Creek, Beaverhead Springs, and throughout the Verde River. It is also found in the Gila River and the Rio Yaqui

Biology

Roundtail chub is very prolific in nature.

Diet

Roundtail chub is a voracious predator, consuming large amounts of fish, crayfish, frogs, and insects. Roundtail chub adults primarily consume aquatic and terrestrial insects, other fishes, and sometimes algae. Roundtail chub juveniles fish eat smaller insects, crustaceans, and algae.

Conservation

The decreasing population of the roundtail chub (Gila robusta) is primarily due to the result of habitat loss, and predation, and competition by non-native fish. Although the populations in the Salt and Verde Rivers were stable ten years ago, they have been exponentially decreasing. Recent conservation efforts include more research to determine the mechanisms of the their sudden disappearance, and population surveys conducted by the Arizona Game and Fish and US Forest Service (in progress).

Arizona Game and Fish Department considers roundtail chub a sport fish. They put up a strong fight for anglers, and the meat is described as "firm, white and very mild tasting." Intermuscular bones or floating bones are present, which can be cut out prior to cooking.

Gila robusta is a candidate endangered species of the United States Fish and Wildlife Service, under the Endangered Species Act criteria.

References

• Ira La Rivers, Fishes and Fisheries of Nevada (University of Nevada Press, 1994), pp. 388–390
• Froese, Rainer; Pauly, Daniel (eds.). "Gila robusta". FishBase. May 2006 version.