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Photo Courtesy of Utah Division of Wildlife Resources
Roundtail Chub
Gila robusta
NatureServe conservation status
Global (G-rank): G3
State (S-rank): S2
- Reason: Few occurrences and increasingly unsuitable habitat conditions throughout the Utah range.
External links
General information
The roundtail chub, Gila robusta, is a fairly large minnow native to the Colorado River system of the western United States. The species prefers large rivers, and is most often found in murky pools near strong currents in the main-stem Colorado River, and in the Colorado River's large tributaries. Although locally common in places, roundtail chub have been reduced in numbers and distribution due to flow alteration and the introduction of exotic fishes.
Roundtail chub eat terrestrial and aquatic insects, mollusks, other invertebrates, fishes, and algae. The species spawns over areas with gravel substrate during the spring and summer. Eggs are fertilized in the water, and then drop to the bottom where they adhere to the substrate until hatching about four to seven day later.
Species range
This fish is endemic to the Colorado River drainage where it occurs in the large, mainstem rivers and also in tributary streams, particularly in the low-gradient reaches of large tributaries.
Migration
White (2005) tracked 6 roundtail chubs in the Navajo River, a tributary of the San Juan River. Individuals made substantial spawning migrations; some moved between the Navajo and San Juan rivers and between pool and riffle habitats within each river. The average distance moved between contacts was 650 meters and the maximum was over 13 kilometers.
Habitat
This species inhabits main channels of large rivers. Lanigan and Berry (1981) reported, in the White River, Uintah County: "Young roundtail chubs commonly were found in pools where there was some water movement, such as those below riffles, and pools formed by debris on the margins of the river. Adults, which are well adapted to swift current, were found in deeper water than were the young."
Food habits
Opportunistic; eats available aquatic and terrestrial insects, gastropods, crustaceans, fishes, and sometimes filamentous algae (Sublette et al. 1990). Subspecies "JORDANI" apparently prefers algae, which may be an important food in other populations (Sigler and Sigler 1987). See Tyus and Minckley (1988) for information on the possible importance of the Mormon cricket as a food source.Schreiber and Minckley (1981) reported that subadults and adults in Aravaipa Creek, Arizona, ate a total of 21 items which included ephemeropterans, odonates, belostomatids, trichopterans, dipterans, coleopterans, hymenopterans, Meda fulgida, Agosia chrysogaster, Sceloporus magister, algae, detritus and sand. These chubs were sampled in January, April, July, and October of 1975, and again in January of 1976.
Ecology
The roundtail chub is associated with a native fish fauna that varies over its extensive range but would typically include speckled dace (RHINICHTHYES OSCULUS), one or more CATOSTOMAS sp., and one or more PANTOSTEUS sp. Historically it was also associated with woundfin (PLAGOPTERUS ARGENTISSIMUS), bonytail chub (GILA ELEGANS), humpback chub (GILA CYPHA), squawfish (PTYCHOCHEILUS LUCIUS), and razorback sucker (XYRAUCHEN TEXANUS), now extirpated over most of their former range (Minckley 1973).
Reproductive characteristics
In the lower Colorado River basin, breeding colors and tubercles in Gila species have been noted from December to June (primarily February to June), mature gonads from December to June (primarily April to June), and spawning activity from March to May (primarily April to May) (Neve 1976, Minckley 1981). In the upper Colorado River basin, Gila species spawn from mid- to late June or early July, when water temperatures reach 18 C (Vanicek and Kramer 1969). Roundtail chubs mature between 2-5 years of age. A few may live to an age of up to 20 years (Scoppetone 1988), but the largest and oldest individuals are more commonly around 7-10 years of age and about 400 mm TL (Bezzerides and Bestgen 2002).
Threats or limiting factors
Evident population declines are following the pattern of range reduction and fragmentation seen in populations of other large-river fish species occurring in the Colorado River System. Roundtail chub populations have been affected by the dramatic alteration of habitat in the Colorado River and its tributaries following the construction of large reservoirs in this system. Changes in the physical properties of the aquatic habitat can directly affect survivorship and reproductive success. Habitat conditions have allowed introduced populations of nonnative fish species to flourish, affecting roundtail chub populations through predation or competition.
References
- Biotics Database. 2005. Utah Division of Wildlife Resources, NatureServe, and the network of Natural Heritage Programs and Conservation Data Centers.
- Sigler, W. F. and J. W. Sigler. 1996. Fishes of Utah[:] a natural history. University of Utah Press. Salt Lake City. 375 pp.
