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Abstract
Migratory fishes have evolved to deal with the unique environmental characteristics of their destination and migratory corridor habitats, but these environments are changing, potentially compromising the continued persistence of migratory populations. The most iconic and conspicuous fish migrations traverse narrow riverine corridors between the ocean (or other large bodies of water) and smaller streams. Humans have adversely affected these habitats by constructing migration barriers, changing land cover, and changing the climate. Investigating the relationship between environmental variation and fish migration is a crucial prerequisite for mitigating these effects. In this dissertation, I quantify the relationship between environmental variation and migration, and evaluate how that relationship affects the population biology of two fishes in two study systems: Chinook salmon (Oncorhynchus tshawytcha) that spawn in central Idaho, USA, and lake sturgeon (Acipenser fulvescens) that spawn in the Niagara River, USA/Canada. For lake sturgeon, I demonstrate that female lake sturgeon, but not males, are more likely to breed in years with warmer spring water temperatures, suggesting that climate warming leads female lake sturgeon to spawn more frequently. For Chinook salmon, I quantify how spatiotemporal variation in habitat variables in a pristine watershed influence the distribution of breeding, and how this variation buffers salmon from predicted changes in water temperature arising from climate change. I also develop a life-cycle model to investigate dam removals along the Snake River migration corridor and find, with conservative assumptions, that the regional population growth rate of Chinook salmon increases by ~7% per dam. Dam removal is predicted to increase the proportion of local sites that support positive population growth, from 24% (0 dams removed) to over 60% (4 dams removed). These results are invariant across three spatial scales of inference.
My results add to the disciplines of ecology and conservation biology by developing and applying cutting-edge statistical models that integrate data from multiple sources to assess ecological dynamics. These models can be used to inform future conservation and management actions for Chinook salmon, lake sturgeon, and other imperiled, migratory fishes.