INDIVIDUAL BASED MODELLING APPROACH TO THERMAL REFUGE USE BY MIGRATING ADULT SALMON AND STEELHEAD: Part II
Snyder, M., Joe Ebersole, N. Schumaker, R. Comeleo, J. Dunham, M. Keefer, S. Heppell, D. Keenan, AND J. Palmer. INDIVIDUAL BASED MODELLING APPROACH TO THERMAL REFUGE USE BY MIGRATING ADULT SALMON AND STEELHEAD: Part II. 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 understanding impacts of climate change. Patches of coldwater known as thermal refuges, are a potential mitigation strategy to help mitigate the negative effects of increasing stream temperatures. These features can vary in space and time and have the potential to be critical for coldwater fish at certain times when rivers would otherwise be too warm for survival. More research is needed on the relative size, spacing, and quality of refuges needed to protect salmon and steelhead populations currently and under future climate conditions. This presentation will describe parameterization of 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.
Diadromous fish populations in the Pacific Northwest face challenges along their migratory routes from declining habitat quality, harvest, and barriers to longitudinal connectivity. Changes in river temperature regimes are producing an additional challenge for upstream migrating adult salmon and steelhead, species that are sensitive to absolute and cumulative thermal exposure. Adult salmon populations have been shown to utilize cold water patches along migration routes when mainstem river temperatures exceed thermal optimums. We are employing an individual based model (IBM) to explore the costs and benefits of spatially-distributed cold water refugia for adult migrating salmon. Our model, developed in the HexSim platform, is built around a mechanistic behavioral decision tree that drives individual interactions with their spatially explicit simulated environment. Population-scale responses to dynamic thermal regimes, coupled with other stressors such as disease and harvest, become emergent properties of the spatial IBM. Other model outputs include arrival times, species-specific survival rates, body energetic content, and reproductive fitness levels. Here, we discuss the challenges associated with parameterizing an individual based model of salmon and steelhead in a section of the Columbia River.