Estimates of the age and growth of roundtail chub Gila robusta were made by analyzing thin cross sections of sagittal otoliths from 280 specimens collected in the upper Verde River, Arizona, from January 1997 to December 1999. Marginal increment analysis indicated that a single annulus completed formation between January and May. The use of otoliths to age roundtail chub was further validated using otoliths of known-age, hatchery-reared fish for which (upon examination) the number of annuli agreed 100% of the time with the true age of the fish. In addition, daily increments were observed on sagittal otoliths of age-0 roundtail chub and, when counted, agreed with the true age of fish 70% of the time; daily ring counts were within 1 [...]
