ABSTRACTREGIONAL INFLUENCE OF LANDSCAPE FEATURES AND PROCESSES ON FLUVIAL FISH ASSEMBLAGESByDarren Jay Thornbrugh Habitat fragmentation, degradation and loss are dominant reasons for global declines in biodiversity of fishes in stream systems, and humans have drastically modified landscapes drained by streams due to activities including urbanization and agriculture. Such human land uses are known to change stream habitats through inputs of excess nutrients, sediments, or toxics and through changes in stream flow and thermal regimes, and human land uses have been shown in many studies to negatively affect stream habitats and the fishes they support. Despite this understanding, degradation of stream habitats and fishes continues globally, and freshwater fishes remain one of the most threatened groups of organisms on the planet. Less understood are the specific mechanisms by which land uses affect stream habitats and how these can vary by region, and how additional landscape-scale characteristics may alter effects of human land uses, resulting in regionally-specific responses in stream fishes to stressors. Such differences across regions may render one locale more sensitive to biodiversity loss or fish assemblage change from the same magnitude of anthropogenic disturbance in the landscape and confound efforts to develop and apply specific actions to conserve biodiversity of stream fishes. The goal of this study is to help address these limitations in understanding. In these chapters, I characterize important natural landscape factors and human land uses influencing distributions and abundances of stream fishes across large regions in both Michigan and within five freshwater ecoregions in the eastern portion of the United States. The results show major regional patterns of natural landscape factors and human stressors that affect fluvial fishes and how these factors vary in influence across regions. This more in-depth understanding of landscape influences on fluvial fish assemblages will allow managers to better account for this regional variability when working to protect and conserve freshwater fisheries and biodiversity of fluvial fish assemblages from both current and future threats.
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