Graduate Thesis Or Dissertation

 

Evaluating Fish Rescue as a Drought Adaptation Strategy for Imperiled Coho Salmon: A Life-Cycle Modeling Approach Public Deposited

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  • Projected intensification of drought as a result of climate change may reduce the capacity of streams to rear fish, exacerbating the challenge of recovering ESA-listed salmon populations. Without management intervention, some stocks will likely go extinct as stream drying and fragmentation reduce juvenile survival to unsustainable levels. To offset drought-related mortality, fish rescue programs have proliferated, whereby juvenile salmonids are captured and transferred to offsite rearing facilities. However, efficacy of this potential conservation tool remains poorly understood. I developed a life cycle model to examine the implications of fish rescue on coho salmon abundance across serial life stages. The model operates under the assumption that fish rescue improves juvenile survival but may decrease smolt-to-adult return rates, either through lower marine survival or increased straying as a result of offsite rearing. The simulation model examines scenarios across various quantities of rescued fish, time in captivity, drought severity, and reduced smolt-to- adult return rates. My results indicate that rescue increased adult returns and lowered extinction risk, particularly for fish captively reared for 1 year but decreased adult returns and increased extinction risk for fish reared only over summer when smolt-to-adult return rates were low. The findings suggest that fish rescue with long holding periods of approximately 1 year function more like a stock enhancement program than a drought adaptation tool, so its potential effects on adult returns should be evaluated with caution.
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  • Funding provided by the Northwest Climate Adaptation Science Center
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