Thesis
Modeling the effects of pesticides and environmental stressors on spring Chinook salmon populations in the Yakima River Basin, WA
Washington State University
Master of Science (MS), Washington State University
2018
Handle:
https://hdl.handle.net/2376/101558
Abstract
Populations are often the endpoints of interest to managers in Ecological Risk Assessments (ERAs). However, many population-level ERAs do not integrate metapopulation dynamics, such as dispersal between locally adapted subpopulations, and thus preclude an understanding of how population viability is affected by toxicants and environmental stressors at a landscape scale. A stochastic matrix metapopulation model was developed using demographic data for three locally adapted spring Chinook salmon (Oncorhynchus tshawytscha) subpopulations and one hatchery subpopulation in the Yakima River Basin (YRB), WA. This model was simulated for 24 exposure scenarios, each with 200 simulations of a 50-year metapopulation projection. Subpopulation size outcomes from the simulations were incorporated as the endpoint of an ERA (Bayesian Network- Relative Risk Model, BN-RRM) that integrates the seasonal effects of organophosphate insecticides and environmental stressors (water temperature and dissolved oxygen) on Chinook salmon into a single probabilistic framework. Risk was defined as the probability that a subpopulation would decline from the initial abundance (500,000 individuals per subpopulation). Results of this ERA indicated that risk for wild spring Chinook subpopulations was higher (97% for the American River and 74% for the Naches River subpopulation) than for non-wild subpopulations experiencing high dispersal with a local hatchery (30% for both the hatchery and hatchery-supplemented subpopulations). A seasonal effect of stressors, driven primarily by high water temperatures in summer, was also detected where summer had the highest risk (68.7%) and winter had the lowest risk (52%). Environmental stressors made up a greater proportion of total risk in most scenarios than exposure to organophosphates. These results suggest that metapopulation spatial structure, local adaptation of conspecific populations, and seasonal differences in exposure to stressors impact the distribution of risk at the landscape scale. This method of using site-specific metapopulation model simulations as a probabilistic ERA endpoint shows promise for estimating the spatiotemporal impacts of stressors on Endangered Species Act (ESA)-listed species at the metapopulation level, where metapopulation dynamics and spatial structure create complex risk dynamics.
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Details
- Title
- Modeling the effects of pesticides and environmental stressors on spring Chinook salmon populations in the Yakima River Basin, WA
- Creators
- Chelsea Jane Mitchell
- Contributors
- John D. Stark (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525092001842
- Language
- English
- Resource Type
- Thesis