Population characteristics and movement of roundtail chub in the lower Salt and Verde Rivers, Arizona

Bryan, Scott; Robinson, Anthony

During April 1999- August 2000, we PIT tagged 877 roundtail chub in the lower Salt and Verde rivers to aid in .determining their local life history; including habitat use, population characteristics, and general movement. In addition, we radio-tagged 20 roundtail chub in the two rivers in 2000 and tracked their movement over a five month period (March- July). Habitat use was consistent with existing literature, with roundtail chub inhabiting pool-glide complexes that were adjacent to swift moving riffles. Over 6,400 roundtail chub (95% Cl = 5,048-8,397) were estimated to occupy the lower Salt and Verde rivers from mark-recapture data. Roundtail chub were larger in size than found in most river systems, attaining lengths up to 502 mm and weights up to 1,406 g. Length-frequency histograms of round tail chub collected in the two rivers show a disparity of juvenile fish and several"missing" year-classes. This may be a reflection of a lack of precipitation and spring runoff, which in tum appear to have an impact on reproduction and recruitment. Both radiotelemetry and PIT tagging data indicated that roundtail chub were somewhat sedentary in the lower Salt and Verde rivers during our study. The maximum distance traveled was approximately 7.5 km, but the mean distance traveled by all roundtail chub was less than 2.5 km. There was no apparent movement related to spawning events. Although we determined that the roundtail chub population in the lower Salt and Verde rivers is larger and more stable than previously reported and we collected important baseline infonnation, more work is needed to fully understand the local life history of this unique population.