Effects of flooding on recruitment of roundtail chub, Gila robusta, in asouthwestern river.

摘要

Floods are an important abiotic factor regulating stream fish assemblages. Alterations to the natural hydrograph (e.g., water storage and diversion dams) which have reduced or eliminated flooding have been blamed, in part, for the decline of many native fishes in the desert Southwest. Proposals to divert water from the upper 72 km of the Verde River of Arizona have raised concerns about the sustainability of native fish populations. I examined the relationship between late winter/early spring flooding and recruitment of roundtail chub, Gila robusta, to age I in an unregulated section of the upper Verde River, Arizona, and determined if significant differences in mean catch per unit effort (CPUE) of age 1 roundtail chub existed over an 11-year period. A strong positive relationship between maximum mean daily discharge in year, and mean CPUE of age I roundtail chub in year,, was apparent. Mean CPUE of age I roundtail chub significantly increased or remained high in years following a flood in late winter/early spring of the previous year. and significantly decreased or remained low in years without flooding. Conversely, mean CPUE of subadult/adult roundtail chub did not significantly differ among years; thus, whether or not periodic strong year-classes are needed to maintain adult populations is uncertain. Nonetheless, recruitment of roundtail chub, and possibly other native fishes, to age 1 appears to be dependent on late winter/early spring floods, and a reduction in flood frequency likely would be detrimental to native fishes.