Mechanisms Associated with Success and Failure of the Anadromous Migration of Atlantic Salmon

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Lennox, Robert




Nearly every animal accomplishes life history tasks that enable growth and fecundity, factors that determine the ultimate fitness of an individual's life, by moving. Migration allows individuals to maximize their potential fitness by exploiting temporal differences in productivity of discrete habitats. Migratory species have high cultural and ecological importance as vectors linking and fertilizing separate ecosystems; however, their reliance on multiple habitats and long-distance movements exposes them to stressors. I applied electronic tagging to observe the behaviour of wild Atlantic salmon, a migratory fish threatened by climate change, habitat destruction, disease, and overexploitation. Observations were applied to evaluate how stressors affected migration success. Atlantic salmon were generally tolerant to stressors as they migrated upriver to spawning grounds. Resumption of migration was delayed for stressed salmon relative to a control group (Chapter 2) and captured salmon selected spawning grounds significantly lower in the river than expected based on the distribution of uncaught fish (Chapter 3). Salmon also exhibited movement away from holding sites when captured late in the season (Chapter 4) but the extent of movement was not significantly different from expected based on observations in Chapter 3. Ultimately, most salmon survived stressors and many were recaptured by recreational anglers (Chapter 5); mortality was best predicted by water temperature at capture (Chapter 6). Selection against some migratory behaviours such as early run timing is ongoing, but stabilizing selection for large body size is predicted to preserve migration phenotypes in Atlantic salmon. Oncoming changes to climate, however, were predicted to delay the freshwater entry of salmon (Chapter 7) and may result in multiple stressors during migration. Further research is needed into the cumulative effects of multiple stressors and how they may operate on imperiled salmon populations. Long-term consequences may manifest through carryover effects that reduce the probability of overwinter survival and iteroparity, insidious consequences that should be further investigated. This thesis provides a framework for addressing questions about the survival, delay, and extent of movement of animals encountering anthropogenic stressors during migration. Future work may follow this model to investigate migration and evaluate the impact of stressors on migration success.


Fisheries and Aquaculture




Carleton University

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Theses and Dissertations

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