Project
Understanding hypoxia’s impact on Lake Erie fisheries under altered nutrient and climate conditions
Eutrophication-driven bottom hypoxia has become a growing problem worldwide, yet its long-term impact on fish populations and the fisheries they support remains speculative in most ecosystems. This uncertainty includes Lake Erie, where eutrophication-driven hypoxia has reemerged as a problem in its central basin during recent decades. A full understanding of how hypoxia has and will continue to influence fishery dynamics in the face of planned phosphorus abatement programs and continued climate change is lacking. To help agencies achieve this ability, we will use a multi-modeling approach to investigate the degree to which hypoxia can influence fisheries production, emphasizing lake whitefish and walleye, which differ in their physiological needs and foraging habits. We hypothesized that bottom hypoxia has influenced the spatial distribution of harvest of both species by modifying habitat quality, with its effect being greater for lake whitefish, a coldwater benthivore, than for walleye, a cool-water benthopelagic piscivore. Further, we hypothesized that impending nutrient abatement programs designed to mitigate bottom hypoxia would differentially affect the capacity of central Lake Erie to support fisheries production, with climate change modulating these effects through its influence on vital habitat features (e.g., temperature, prey production, and water clarity). To test these hypotheses, we will: 1) link output from existing water quality models to newly developed habitat quality models for walleye and lake whitefish to identify parsimonious predictive models of fisheries harvest in central Lake Erie and forecast how impending nutrient reduction and climate change will affect the harvest of both species (Objective 1); and 2) use Ecopath with Ecosim to assess how impending nutrient reduction and climate change will affect fish production in central Lake Erie (Objective 2). By completing these objectives, we aim to help Lake Erie Committee agencies better understand the degree to which they need to consider hypoxia in their management decision-making, as well as learn how anticipated variability in bottom hypoxia associated with planned nutrient reductions and continued climate change will influence fishery harvests and production potential. This understanding could also help LEC agencies better manage the expectations of their constituents (recreational anglers, charter boat captains, commercial netters) such that they do not exceed the lake’s production potential as it changes with nutrient abatement and climate change.