Fish assemblage restoration in the lower Blue River, Arizona

Authors: Brian Hickerson, Anthony Robinson, Kent Mosher

Year: 2019

Abstract

Opportunities for multi-species native fish restoration efforts are sparse in the desert southwest and such efforts are not always successful. Native fish restoration efforts are often impeded by biotic factors that can potentially be controlled (e.g., presence of nonnative fishes), but equally important are the abiotic factors that cannot be controlled (e.g., annual discharge and flow regime). The Blue River native fish restoration project began in 2009 with the goal of increasing the abundance of existing Loach Minnow, Rhinichthys cobitis, and establishing Spikedace, Meda fulgida, and Roundtail Chub, Gila robusta. The project involved several steps including the completion of a fish barrier to exclude nonnative fish, removal of nonnative piscivores in the lower portion of the river above the barrier, stocking of native fishes, and annual monitoring. The fish community of the Blue River experienced a significant shift from roughly equal proportions of native and nonnative fish in 2012 to an exclusively native fish community dominated by the three focal species in 2018. Nonnative piscivore removal efforts were successful as Channel Catfish, Ictalurus punctatus, were last captured in 2013 and Green Sunfish, Lepomis cyanellus, in 2016. We evaluated whether relative abundance of native fish was related to a number of factors including: time since stocking, relative abundance of nonnative fishes, and several discharge metrics using generalized linear modeling. Time since stocking best explained the relative abundance of the three focal species, but discharge may also play a role. Relative abundance of pre-existing native fishes was most influenced by relative abundance of nonnative predators. The distribution of the three focal species within the mainstem increased rapidly from 2012 to 2018 and Roundtail Chub were detected several miles upstream in a major tributary in 2019. A comprehensive approach to native fish restoration resulted in the eradication of nonnative fishes and the establishment of robust populations of sensitive native species in the lower Blue River. By evaluating factors that contributed to successful establishment of focal species, we can implement future restoration efforts with a more informed approach, ultimately resulting in additional successful restoration efforts.