Hydrological Disturbances Regimes in Aravaipa Canyon, Arizona: Impacts on Native and Non-Native Fish Communities

Authors: Peter Reinthal, Jessica Gwinn

Year: 2016 (xlviii)

Abstract

Aravaipa Creek is the preeminent native fish assemblages remaining in the Gila Basin and is home to two or three federally li sted endangered or candidate fish species. Hydrologic baseflow and periodic cyclonic and monsoonal flooding events are needed to ensure that (1) diversity and variability of aquatic habitats are maintained for the seven native fish species, and (2) popul ations of exotic species continue at low abundance or are eventually removed from the system. Variability in flow is considered necessary for both the long term perseverance and survival of native fishes and the periodic extrication of exotic individuals from the system. Here we present data from a 50 year monitoring period for Aravaipa fishes that examines short and long-term variation in fish populations. Native species show considerable variability in population abundance and there is a positive relationship betwee n baseflow and native fish populations, but exotic fish populations do not show the same response. After periodic flooding, populations of exotic species are, to a large extent, significantly reduced. Variability is important for the persistence of the native fish populations. In contrast, lack of flow variability results in an increase in nonnative fishes. These results are critical for a scientific evaluation of a water extraction model (Opportune Extraction Model, [OEM]) for the extraction flood flows that some consider surplus to meet biological, hydrological, and physical processes for protection of the wilderness area.