Roundtail Chub (Gila robusta): Species Profile

The roundtail chub, Gila robusta, is a native freshwater fish found in the western United States. It belongs to the minnow family, Leuciscidae, which includes various dace and chub species. It has historically played an important role in the Colorado River basin ecosystem.

Physical Characteristics

The roundtail chub has a streamlined, elongated body, deeper near the dorsal fin and tapering to the tail. Its head is flattened or slightly concave, with a large mouth overhung by the snout and extending to the front of the eye.

It is olive-gray or brownish on its back, transitioning to a silvery or white underside. During breeding, males develop red-orange hues on their lower cheeks and paired fins. They have a large, forked tail fin, with nine rays on their dorsal and anal fins. Adults typically reach 25–30 cm (10–12 in), though some grow up to 49 cm (19.5 in).

Habitat and Geographic Distribution

Native to the Colorado River drainage basin, including its major tributaries, its historical range spans Arizona, Colorado, New Mexico, Utah, Wyoming, and parts of northwestern Mexico. It prefers warm streams and large rivers with low to moderate gradients. They inhabit deep pools, rocky runs, and eddies, often concentrating in swift water below rapids or murky pools near strong currents.

Diet and Life Cycle

It has an omnivorous diet. Larvae eat diatoms and filamentous algae; juveniles consume aquatic insects (e.g., midges, mayflies), crustaceans, and algae. Adults add terrestrial insects, other invertebrates, plant matter, small fish, and occasionally small reptiles to their diet.

Spawning occurs in late spring and early summer, coinciding with snowmelt runoff when water temperatures reach 18 °C (64 °F). Adhesive eggs are broadcast over gravel substrates in shallow, slower-moving waters, adhering to the bottom. Eggs hatch in four to seven days, and individuals mature between two to five years. While some live up to 20 years, most reach 7-10 years.

Conservation Status

Roundtail chub populations have significantly declined across much of their historic range. This is due to habitat modification, primarily from dam construction and water diversions. These alterations fragment habitats, change river flows, and lead to warmer water temperatures, which are less favorable for native fish.

Another factor is the introduction of non-native predatory fish, such as smallmouth bass, northern pike, and channel catfish. These predators compete with and prey on roundtail chubs, especially their early life stages. While considered a “species of concern” with decreasing distribution and abundance, its official protection status varies by state. However, some populations show stabilization or increases due to ongoing conservation efforts.

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