Standardized Monitoring of Native and Nonnative Fishes in the Colorado River in Glen and Grand Canyons, AZ

The Glen Canyon Dam Adaptive Management Program advises the Secretary of Interior on the effects of dam operations and related management actions on Colorado River resources in Glen and Grand Canyons. Key resources include native and nonnative fishes with the program’s fish monitoring and research efforts focused on native Humpback Chub Gila cypha, an endangered species, and nonnative Rainbow Trout Oncorhynchus mykiss, a popular sport fish. Monitoring activities provide information on population status and trends, species distribution and habitat use, and diet. Research is directed at minimizing or resolving key areas of uncertainty.  These include identifying and understanding factors that control Humpback Chub and Rainbow Trout population dynamics, determining the implications of interactions between native and nonnative fishes, and evaluating the effects of dam operations. Given the complexity and scale of the highly managed Colorado River, long-term, standardized monitoring is an essential component of detecting change in response to environmental variability, management actions, and large-scale experiments. Challenges include issues of scale related to effectively monitoring both an abundant nonnative and a rare native species. Fisheries information is provided to managers and stakeholders to support an adaptive management process designed to protect and benefit resources downstream of Glen Canyon Dam.