This project is building an individual-based trout model for U.S. Forest Service research sites on Little Jones Creek, Smith River basin, Del Norte County, northwest California. The model has now been applied to sites on the middle and upper mainstem of Little Jones Creek and on one small tributary. The principal investigator on this project is Dr. Bret Harvey, of the U.S. Forest Service's Redwood Sciences Laboratory.The model is being used for both research and resource management applications. Research applications include testing hypotheses about the mechanisms of habitat selection by stream salmonids over daily and seasonal time scales, and evaluating the importance of small tributaries to stream trout populations. If validated, the model will be useful for such management applications as predicting the individual or cumulative effects on salmonid populations of timber harvest, water diversion, and habitat alteration.
The study site has been used for previous studies of trout movement and habitat selection. The modeling sites were established in 1999 and habitat data collection has been completed. Redwood Sciences Laboratory scientists continue to monitor trout populations and conduct controlled experiments to test and improve components of the model.Key new features of this model: The model includes barriers to upstream movement. As our model assumes fish make fitness-seeking choices among habitat patches they are familiar with, we developed an algorithm for how fish decide whether to move downstream over a barrier that prevents them from returning to their current site. The effects of turbidity on drift food intake and predation by terrestrial animals is now included: turbidity decreases drift feeding reactive distances and terrestrial predation risk. Predation by trout is now a function of predator density, making predation (as well as food intake) density dependent.Results to date: Preliminary simulations have examined the long-term effects of variation in stream flow and turbidity on trout abundance, growth, and mortality sources. These analyses are conducted with multiple five-year simulations that vary by flow.
Products to date include a model formulation document, an updated software users guide, and a submitted manuscript testing the model's ability to predict trout habitat selection.
Related work:Harvey, B. C. (1998). Influence of large woody debris on retention, immigration, and growth of coastal cutthroat trout (Oncorhynchus clarki clarki) in stream pools. Canadian Journal of Fisheries and Aquatic Sciences 55(8): 1902-1908.
Harvey, B. C., R. J. Nakamoto, et al. (in prep.). Influence of large woody debris and a bankfull flood on movement of adult resident coastal cutthroat trout (Oncorhynchus clarki clarki) during fall and winter. Canadian Journal of Fisheries and Aquatic Sciences 56(6): 2161-2166.