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Individual Based Modelling of Fish Migration in a 2-D River System: Model Development and Case Study
Citation:
Snyder, M., N. Schumaker, J. Ebersole, R. Comeleo, J. Dunham, M. Keefer, A. Brookes, J. Halama, P. Leinenbach, J. Palmer, AND D. Keenan. Individual Based Modelling of Fish Migration in a 2-D River System: Model Development and Case Study. International Association for Landscape Ecology, Ft. Collins, CO, April 06 - 11, 2019.
Impact/Purpose:
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.
Description:
Conditions within migration corridors that organisms move through can strongly influence their probability of surviving and arriving to their destinations. Diadromous fish populations in the Pacific Northwest face challenges along their migratory routes from declining habitat quality, harvest, and barriers to longitudinal connectivity. The variety of interacting factors influencing migration success make it challenging to assess management options for improving conditions for migratory fishes such as imperiled anadromous salmon and steelhead species along riverine migration corridors. We describe a migration corridor simulation model which integrates complex individual behavior, responds to variable habitat conditions over large areas, and is able to link migration corridor conditions to fish fitness outcomes. Our model, developed within HexSim, 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 harvest, become emergent properties of the migration corridor simulation model. Outcomes of the migration corridor simulation model include passage time, energy use, and survival, which can be used to evaluate trade-offs of behavioral thermoregulation on fish fitness. To demonstrate the potential utility of the simulation model, we describe the sequence of model events and basic model mechanisms. Then, we describe an application of the simulation model to a case study of salmon and steelhead adults in the Columbia River migration corridor.