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VARIATION IN JUVENILE COHO SALMON SUMMER ABUNDANCE: HIERARCHICAL ANALYSIS OF HABITAT EFFECTS
Citation:
COLVIN, M., J. L. EBERSOLE, P. J. WIGINGTON JR, M. CHURCH, J. E. COMPTON, J. P. BAKER, M. A. CAIRNS, S. G. LEIBOWITZ, AND D. WHITE. VARIATION IN JUVENILE COHO SALMON SUMMER ABUNDANCE: HIERARCHICAL ANALYSIS OF HABITAT EFFECTS. Presented at Oregon Chapter American Fisheries Society, Eugene, OR, February 28, 2007.
Description:
Varying habitat conditions found across a stream network during the summer months may limit the abundance of salmonids such as coho (Oncorhynchus kisutch). We examined the abundance of juvenile coho salmon across a stream network in an Oregon coast range basin from 2002 through 2005 to understand the influence of summer habitat and conditions on coho parr abundance. We developed a hierarchical linear mixed effects model to predict habitat unit parr abundance that utilized habitat variables measured during the summer at multiple spatial scales (habitat unit, reach, stream), and an information theoretic approach to select the best approximating model for habitat unit summer parr abundance. The best approximating model fit the data well and contained measures of habitat unit area, temperature, discharge, and water quality. Habitat unit coho parr abundance was positively associated with habitat unit area within stream reaches; however the magnitude of this effect was variable across the stream network. There was a strong negative interaction of minimum summer discharge and pool area indicating that larger pools located in the mainstem of the stream network are not utilized to the same degree as smaller pools. Measure of nitrate, phosphorous, and temperature had small positive effects in the model. This model will be used to complement an analysis of end of summer coho weight and condition and investigate environmental and restoration scenarios.