Dams have dramatically altered riverine systems and are a major contributor to native fish population declines. Dam removal is now a common stream rehabilitation practice in the United States; however, many dams serve important ecological, social, and economic functions, such as flood control, invasive species control, and provision of recreational opportunities. Therefore, dam removal is often contentious among stakeholders and involves making tradeoffs among multiple competing objectives. Decision makers benefit from a thorough evaluation of the ecological, economic, and social consequences and tradeoffs of changes to connectivity using decision analysis and predictive models, yet few examples exist in the literature. The objectives of this research were to use a decision analytic framework and predictive models to evaluate the ecological, economic, and social consequences and tradeoffs of enhancing connectivity for migratory fishes in the Great Lakes basin. In Chapter 1, I used structured decision making to engage a diverse group of stakeholders and rightsholders to evaluate the ecological, social, and economic consequences and tradeoffs of enhancing connectivity for migratory fishes in the Boardman-Ottaway River watershed. The optimal management alternative was passage of native fishes only; however, the optimal alternative varied based on the weight stakeholders might place on each objective. Four weighting scenarios were developed to evaluate the change in optimal management alternative with changes in objective weights. In Chapter 2, an individual-based model framework was developed to forecast the response of migratory fishes to changes in connectivity and applied to predict the change in abundance and growth of six species under various fish passage scenarios on the Boardman-Ottaway River. Population response to barrier removal was species-specific and varied based on initial population size and distribution within the watershed, the number of fish passed upstream, and species life history traits. Species that were found only below the barrier prior to removal benefitted most. Non-native species were found to have greater production potential than native Great Lakes basin species under full passage scenarios. In Chapter 3, I evaluated stocking scenarios for lake sturgeon Acipenser fulvescens to aid decision making in the rehabilitation of an imperiled native Great Lakes basin species. Using the model from Chapter 2, several lake sturgeon stocking scenarios were simulated to forecast the potential time to reach a recovered lake sturgeon population. Sensitivity analysis and expected value of perfect information were used to elucidate key areas of uncertainty. The median time to reach the target abundance was estimated to take between 31 and 91 years, depending on the stocking strategy. The results of this research will help inform decision-makers in the Great Lakes basin on management alternatives for fish passage and restoration that are preferred by stakeholders and that are likely to achieve their objectives.
Read
