Individual-Based Model Formulation for Cutthroat Trout, Little

Railsback, Steven F.; Harvey, Bret C. 2001. Individual-based model formulation for cutthroat trout, Little Jones Creek, California. Gen. Tech. Rep. PSW-GTR-182. Albany, CA: Pacific Southwest Research Station, Forest Service, U. S. Department of Agriculture; 80 p. This report contains the detailed formulation of an individual-based model (IBM) of cutthroat trout developed for three study sites on Little Jones Creek, Del Norte County, in northwestern California. The model was designed to support research on relations between habitat and fish population dynamics, the importance of small tributaries to trout populations, and the usefulness of individual-based models for forest management. The model simulates the full trout life cycle at a daily time step; habitat is modeled at a resolution of several square meters. The major trout activities simulated are spawning, habitat selection (movement), feeding and growth, and mortality. Two feeding strategies are simulated: drift feeding and searching for stationary food. Mortality risks include starvation, aquatic predation, terrestrial predation, high temperature, stranding, and high velocity. Movement maximizes the probability of surviving and attaining reproductive size over a future time horizon. Risks to incubating trout eggs include extreme temperatures, dewatering, and scouring by high flows. The model design approach was adapted from complex adaptive systems theory. Retrieval Terms : cutthroat trout, habitat selection, individual-based model, population model, salmonids The Authors Steven F. Railsback is an environmental scientist with Lang, Railsback & Associates, 250 California Avenue, Arcata CA 95521; e-mail : [email protected]. Bret C. Harvey is a research fish biologist with the Pacific Southwest Research Station, USDA Forest Service, 1700 Bayview Drive, Arcata CA 95521; e-mail: [email protected]. Acknowledgments The Little Jones Creek cutthroat trout model was developed under Research Joint Venture Agreement PSW-99-007-RJVA between the Pacific Southwest Research Station, USDA Forest Service’s Redwood Sciences Laboratory, and Lang, Railsback & Associates (LRA). Collaborative funding for software development and model testing was provided to LRA by the Electric Power Research Institute (EPRI). The trout model software is developed and maintained by Steve Jackson, Jackson Scientific Computing, McKinleyville, California. Jim Petersen, Columbia River Laboratory, U. S. Geological Survey, provided a valuable review of a previous draft of this document. Tom Lisle, Pacific Southwest Research Station, Arcata, California, helped develop the approach we use for modeling redd scouring. The Swarm program at the Santa Fe Institute (Santa Fe, New Mexico) has heavily influenced our approach to fish movement and the overall modeling philosophy. Pacific Southwest Research Station USDA Forest Service General Technical Report PSW-GTR-182 June 2001