Re-Purifying the Virgin (River): Alleviating Native Fish Stressors through Red Shiner Management

Authors: Skyler Hedden, Julie Carter, Brandon Albrecht, Ron Rogers, Kevin Guadalupe, Brandon Senger

Year: 2021

Abstract

Native fish populations, in the American Southwest are in a dire state because of numerous stressors negatively acting upon communities. Often managing these stressors is difficult because of the uncertainty of impact and the synergistically relatedness of such stressors. Nonnative fish removal is a management strategy that is often a priority because of the perceived negative impacts nonnatives impose on native communities and the direct ability to quantify number of nonnatives removed. However, controlling nonnative fish populations can be limited in their temporal and spatial extent, leading to mixed results and benefits to native fish. This study highlights ongoing management strategies in the Virgin River, a tributary to the Colorado River, controlling the negative associations between red shiners (Cyprinella lutresnsis) and the native fish community. Furthermore, we compared alternative management solutions, to ongoing chemical control, by assessing fish responses to flow metrics from 2009-2020. Successful eradication of red shiners has occurred from over 50 miles of the Virgin River. Additionally, flow manipulation strategies may be a viable option for controlling red shiners in reaches where they are still present, as red shiner densities were 60% lower when peak summer flows were higher. Our results suggest that increases in reservoir outflow during monsoonal rains may help reduce red shiner populations in reaches that still contain this species. With the use of multiple management techniques, we may become better able to successfully eradicate and control red shiner populations for the benefit of native fishes across a broad spatial extent.