Red Shiner Eradication: A History of Endangered Species Recovery through Non-Native Removal in the Virgin River

Authors: Sarah Siefken, Rick Fridell, Kevin Wheeler, Melinda Bennion, Martin Schijf, Christian Edwards, Erik Woodhouse, Kody Callister

Year: 2022

Abstract

Native fish populations in arid regions throughout North America are threatened by numerous anthropogenic stressors, including the introduction of non-native fish species. This presentation highlights the Red Shiner, Cyprinella lutrensis, a small minnow native to the Mississippi River Basin that was identified as one of the greatest threats to native fish recovery in the Virgin River. The Virgin River is a tributary to the Colorado River with a unique species assemblage that includes the endangered Virgin River Chub, Gila seminuda, and Woundfin, Plagopterus argentissimus. By the 1980s, Red Shiner had colonized 86 miles of the Virgin River in Utah and decimated native fish populations. In response, the Utah Division of Wildlife Resources and its partners developed a six-phase eradication plan that aimed to completely remove Red Shiner from the Virgin River in systematic, step-wise, downstream phases. Each phase of the eradication plan involved five steps: 1) segmenting the river into manageable phases separated by fish barriers, 2) intensively monitoring Red Shiner distribution, 3) mapping all occupied and potential refuge habitat, 4) mechanically removing Red Shiner whenever possible, and 5) conducting chemical treatments using rotenone. Implementation of the eradication plan began in 1996, and the final phase was completed in 2021 when a chemical treatment was conducted in the Virgin River Gorge along the Utah-Arizona border. The final chemical treatment was a complex, interagency effort that successfully removed Red Shiner from the entire Virgin River in Utah and marked the culmination of nearly three decades of collaborative conservation. Post-treatment sampling indicates that native fishes have recolonized reaches cleared of Red Shiner. Nevertheless, ongoing management will be necessary to address other threats to native fishes and ensure that these enigmatic species persist in the Virgin River.