Understanding climate impacts on American shad recovery, fisheries management, and influences of dams

Introduction and Rationale: American shad, Alosa sapidissima, is an anadromous fish that historically supported economically and culturally important fisheries. The species has declined throughout its range due to changing ocean climate, commercial fisheries, and hydropower dams. In response, NOAA Fisheries Services’ Northeast Fisheries Science Center has undertaken the development of quantitative support tools to quantify the impacts of dam passage performance standards (passage rates and survival) on the productivity of various shad stocks in the Northeast U.S. These models allow for incorporation of uncertainty in life-history parameters, behavioral ecology, human impacts, and environmental drivers. Climate change scenarios have not been integrated into the existing model. This is a critical omission as changing temperatures can significantly alter population productivity through a number of mechanisms that would impact growth and survival in marine and freshwater habitats, as well as the timing, duration, and success of spawning migrations. Riverine and marine temperatures have the potential to influence the net productivity of a population; consequently, changing climate might favor drastically different management strategies with respect to fisheries harvest or dam passage.

Summary of Work: This study proposes to evaluate the influences of multiple factors on the recovery and productivity potential of several American shad stocks in the Northeast U.S. through the integration of climate uncertainty into existing decision support tools. Climate uncertainty will be incorporated by: i) hindcasting historical impacts of ocean temperatures on American shad growth to establish climate-informed reference points; ii) integrating temperature projections from multiple climate models into American shad models to improve resilience of management decisions related to fishery harvest and dam passage; and iii) assessing sensitivity of model projections to climate change in concert with fishery harvest, dam passage performance standards, and uncertainty in life history and ecology of this species.

Relevance to Competition: The proposed work targets Coastal and Ocean Climate Applications (COCA), Competition II: Understanding Climate Impacts on Fish Stocks and Fisheries in the Northeast U.S. Continental Shelf Large Marine Ecosystem. The quantitative consideration of uncertainties associated with life-history characteristics, population benchmarks, and climate change will make management of fishery harvest and dam impacts more robust and resilient. The proposed work also addresses multiple sub-objectives in the NOAA Next-Generation Strategic Plan under the following long-term goals: i) Climate Adaptation and Mitigation; ii) Healthy Oceans; and iii) Resilient Coastal Communities and Economies. This project will directly assess the sensitivity of population productivity and recovery to interactions between predicted climate change, fishery harvest, and management of fish passage as a holistic approach to understanding influences on sustainability of management decisions. The resulting decision-making tool will allow managers to consider uncertainty in climate change and life-history parameters in the decisions they must make with respect to the management of fishery harvest and dam passage for adults and juveniles. The incorporation of temperature effects through multiple biological pathways constitutes a relatively unique approach to fishery stock assessment that will promote resiliency and sustainability in long-term decision making. This tool is readily extended across multiple systems and can support the development of American shad management plans throughout the Northeast U.S. Continental Shelf Large Marine Ecosystem.