Native And Nonnative Fish Community And Food Web Dynamics In Dryland Streams Of The American Southwest

Download or read book Native and Nonnative Fish Community and Food-web Dynamics in Dryland Streams of the American Southwest written by Jane S. Rogosch and published by . This book was released on 2019 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Freshwater biodiversity is at once the most diverse and the most imperiled among the world's ecosystems. In the southwest, regional biodiversity and endemism face challenges imposed by declining water availability and widespread nonnative species proliferation. In this dissertation, I explore how these challenges affect fish community dynamics and native species persistence in dryland rivers, and explore the effectiveness of nonnative removal programs toward native fish conservation. The overarching questions motivating my research are: (1) How are fish communities responding to a changing climate? (2) How does flow intermittence and species origin shape freshwater fish beta diversity across dryland riverscapes? (3) Can we restore native species food-web dynamics through invasive species management? (4) Do strategic and opportunistic removal programs result in measurable, and if so comparable, benefits to native species conservation? Demographic models linking native and nonnative populations to flow dynamics predicted that contemporary declines in the frequency of peak flows, and increases in drought frequency are likely to result in nonnative dominant fish assemblages and diminished native fish populations. I found that intermittent and perennial streams play complementary roles in supporting fish beta diversity, and that contributions of intermittent streams to overall beta diversity were relatively consistent through time, primarily supporting a unique composition of native fishes. Although nonnative species control and removal programs are a common management strategy they have not always been successful. However, I found that nonnative removal efforts allowed native species to recover in their food-web dynamics, by returning to higher trophic levels and isotopic niches comparable to individuals that did not co-occur with nonnative fishes. In a model informed by long-term monitoring programs, I also found that both opportunistic and strategic removal strategies were predicted to decrease native fish extinction probabilities. These results were encouraging, and demonstrated that removal programs can meet recovery goals even over large areas and long after nonnative species are established.