ASSESSING THE IMPORTANCE OF THERMAL REFUGE USE TO MIGRATING ADULT SALMON AND STEELHEAD
Ebersole, Joe, M. Snyder, N. Schumaker, R. Comeleo, J. Dunham, M. Keefer, S. Heppell, D. Keenan, AND J. Palmer. ASSESSING THE IMPORTANCE OF THERMAL REFUGE USE TO MIGRATING ADULT SALMON AND STEELHEAD. Oregon Chapter American Fisheries Society Annual Meeting, Bend, OR, February 28 - March 03, 2017.
Many rivers and streams in the Pacific Northwest are currently listed as impaired under the Clean Water Act as a result of high summer water temperatures. Adverse effects of warm waters include impacts to salmon and steelhead populations that may already be stressed by habitat alteration, disease, predation, and fishing pressures. Much effort is being expended to improve conditions for salmon and steelhead, with increasing emphasis on preparing for future climate change. One climate change adaptation strategy that is gaining increased attention is the potential for thermal refuges to help mitigate the effects of increasing temperatures. Thermal refuges are areas buffered from regional climate effects at a range of spatial and temporal scales. These features can be critical to coldwater fish at certain times when rivers would otherwise be too warm for survival. But it has been difficult to estimate the relative benefits of thermal refuges to salmon and steelhead populations, and more information is needed on the relative size, spacing and quality of refuges needed to adequately protect salmon and steelhead now and under future climate conditions. This presentation will describe an individual-based modeling approach we are using to address and identify key uncertainties for evaluating refuge effectiveness. This abstract contributes to ACE CIVA 2.8.
Salmon populations require river networks that provide water temperature regimes sufficient to support a diversity of salmonid life histories across space and time. The importance of cold water refuges for migrating adult salmon and steelhead may seem intuitive, and refuges are clearly used by fish during warm water episodes. But quantifying the value of both small and large scale thermal features to salmon populations has been challenging due to the difficulty of mapping thermal regimes at sufficient spatial and temporal resolutions, and integrating thermal regimes into population models. We attempt to address these challenges by using newly-available datasets and modeling approaches to link thermal regimes to salmon populations across scales. We discuss the challenges and opportunities to simulating fish behaviors and linking exposures to migratory and reproductive fitness. In this talk and companion poster, we describe an individual-based modeling approach for assessing sufficiency of thermal refuges for migrating salmon and steelhead in the Columbia River.