Life History, Distribution, and Impact of Nonnative Smallmouth Bass (Micropterus Dolomieu) at Range Boundaries in the Columbia River Basin

Download or read book Life History, Distribution, and Impact of Nonnative Smallmouth Bass (Micropterus Dolomieu) at Range Boundaries in the Columbia River Basin written by Erika S. Rubenson and published by . This book was released on 2019 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: Riverine distributions of nonnative smallmouth bass (Micropterous dolomieu) are changing in response to climate change, with smallmouth bass upstream extent increasing as temperatures warm to within its thermal tolerances. Although smallmouth bass continue to shift its distribution into new upstream habitat, little is known about the mechanisms that drive or limit distribution changes, its current distributions in the Columbia River Basin, or the potential impacts expanding smallmouth bass may have on juvenile salmonids, each of which I address in this dissertation. Like most ectotherms, each life history stage (i.e., egg, juvenile, adult) of smallmouth bass has unique thermal optimums and limits that may disproportionately affect successful establishment of new self-sustaining populations. In my first two chapters, I examined the effects of increasingly colder temperatures on spawning patterns, reproductive success, and recruitment across a broad (> 60 km) spatial extent in the North Fork John Day River. In my third chapter, I assessed the inter-annual differences in maximum upstream distribution, seasonal changes in local abundances, and seasonal movement patterns of adult bass to assess the role of adult dispersal in range dynamics. Using these data on reproduction, recruitment, and adult movement patterns, I found key behaviors and physiological constraints that limit or drive range expansion and present management strategies that may be useful to managers tasked with preventing future range expansion of smallmouth bass. In my fourth chapter, I developed a species distribution model of smallmouth bass for the Columbia River Basin using a combination of historical distribution data and environmental DNA (eDNA) distribution data collected at predicted range boundaries. Here, I found that smallmouth bass is widely distributed and predicted to overlap with 3-62% of critical salmonid spawning and rearing habitat. Under a moderate climate change scenario, I found that smallmouth bass is predicted to increase its distribution by over two-thirds, highlighting management challenges throughout the Columbia River Basin. Finally, in my fifth chapter I examine potential competition and predation dynamics in a food web that includes smallmouth bass and juvenile Chinook salmon (Oncorhynchus tshawytscha). Here, I found little evidence for a strong predation or competition threat to juvenile Chinook salmon, suggesting that although smallmouth bass is likely to increase its overlap with native salmonids, its greatest impact to salmonids appears to occur in mainstem habitats. Taken together, the five chapters of this dissertation advance the understanding of the physiology, behavior, distribution, and impact of nonnative smallmouth bass in the Columbia River Basin, which will directly contribute to the management of streams home to myriad threatened and endangered native species.