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VARIATION IN JUVENILE COHO SALMON END-OF-SUMMER SIZE AND ABUNDANCE: HIERARCHICAL ANALYSIS OF HABITAT EFFECTS
Citation:
EBERSOLE, J. L., M. COLVIN, P. J. WIGINGTON JR, J. P. BAKER, M. CHURCH, J. E. COMPTON, M. A. CAIRNS, AND H. LAVIGNE. VARIATION IN JUVENILE COHO SALMON END-OF-SUMMER SIZE AND ABUNDANCE: HIERARCHICAL ANALYSIS OF HABITAT EFFECTS. Presented at American Fisheries Society, San Francisco, CA, September 03 - 05, 2007.
Description:
The size of coho salmon juveniles entering the winter has been shown to influence overwinter survival, and hence may be a useful indicator of linkages between summer habitat conditions and subsequent smolt production. We are investigating habitat-specific demographics of juvenile salmonids in the West Fork Smith River, a 6800 ha watershed in coastal Oregon, to evaluate the relationship of habitat conditions to summer abundance and growth. We are using hierarchical linear mixed effects models to evaluate habitat attributes at multiple spatial scales (habitat unit, reach, and stream levels) that are associated with variation in end-of-summer abundance and condition of juvenile coho salmon (Oncorhynchus kisutch). From 2002 through 2005, abundance was primarily influenced by habitat area. End-of-summer condition varied by watershed location, and was associated with pool area and degree of infestation by a parasitic Neascus-type trematode at the habitat unit level, density at the reach level, and with discharge at the stream level. Year to year variation in size was also evident, likely reflecting annual differences in both overall abundance and habitat conditions. We conclude by discussing the implications of these results for stream management; specifically modifications to physical habitat or trophic status (e.g., spawner carcass planting).