AUTHORS: Randall H. Wilson, Kansas Cooperative Fish and Wildlife Research Unit, Division of Biology, Kansas State University
Daniel S. Sullins, United States Geological Survey, Kansas Cooperative Fish and Wildlife Research Unit, Kansas State University
Keith Gido, Division of Biology, Kansas State University
ABSTRACT: The Colorado pikeminnow (Ptychocheilus lucius), a federally endangered fish species, historically inhabited much of the Colorado River Basin. Despite extensive restocking efforts in the San Juan River, New Mexico, self-sustaining populations of Colorado pikeminnow have not been established. One potential factor contributing to this failure is predation by avian piscivores, particularly the Great Blue Heron (Ardea herodias) and the Common Merganser (Mergus merganser). Our study aims to quantify predation loss of Colorado pikeminnow to these avian predators, assess avian predator abundance along the San Juan River from Fruitland, NM, to the Four Corners Bridge, and evaluate their habitat use along the river. We will employ a Before-After Control-Impact study design, I will deploy approximately 100 trail cameras prior to the release of Colorado pikeminnow, monitoring for a duration of about two years following stocking. Additionally, point count surveys and behavioral observations will be conducted, alongside vegetation surveys to gain insights into the habitat use of these avian predators. Data collection is set to commence in October 2024. Preliminary analyses of eBird data indicated that Common Merganser abundance peaks from December to February, while Great Blue Herons were most abundant during the fall migration, which coincides with the timing of Colorado pikeminnow stocking. By assessing rates of predation on Colorado pikeminnow, estimating the abundance of avian predators, and exploring their ecological requirements, this research aims to provide critical insights for fishery managers. Our results may also inform other fish stockings by enhancing the understanding of the impacts of avian predation on stocked fish populations. Ultimately, this study seeks to inform conservation strategies to improve the survival and establishment of Colorado pikeminnow in the San Juan River ecosystem.
