Modeling Stream Network-Scale Variation in Coho Salmon Overwinter Survival and Smolt Size
DOI: 10.1577/T08-047.1
Title: Modeling Stream Network-Scale Variation in Coho Salmon Overwinter Survival and Smolt Size
Journal Title: Transactions of the American Fisheries Society
Volume: Volume 138
Issue: Issue 3
Publication Date: May 2009
Start Page: 564
End Page: 580
Published online: 9 Jan 2011
ISSN: 0002-8487
a U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Western Ecology Division , 200 SW 35th Street, Corvallis, Oregon, 97333, USA
b Department of Natural Resource Ecology and Management , Iowa State University, 339 Science I , Ames, Iowa, 50011, USA
c Oregon Department of Fish and Wildlife, 63538 Boat Basin Drive , Charleston, Oregon, 97420, USA
d U.S. Forest Service, Pacific Northwest Research Station , Corvallis Forestry Sciences Laboratory, 3100 Jefferson Way , Corvallis, Oregon, 97331, USA
e Dynamac Corporation, 200 SW 35th Street , Corvallis, Oregon, 97333, USA
Abstract: We used multiple regression and hierarchical mixed-effects models to examine spatial patterns of overwinter survival and size at smolting in juvenile coho salmon Oncorhynchus kisutch in relation to habitat attributes across an extensive Stream network in southwestern Oregon over 3 years. Contributing basin area explained the majority of spatial variation (R 2 = 0.57-0.63) in coho salmon overwinter survival (range = 0.02-0.63), with highest survival rates observed in smaller headwater and intermittent Streams. Other habitat attributes, including proportional pool area, percent exposed bedrock substrate, percent broadleaf canopy cover, and adult salmon carcass density, were relatively poor predictors of survival. Indices of individual fish condition, including fall parr fork length, condition factor, and parasite infestation rates, were also relatively uninformative in coho salmon overwinter survival models. Coho salmon smolt length was primarily a function of length at the time of fall tagging, but Stream type, contributing basin area (positive effect), thermal history (positive effect), and black spot infestation (i.e., trematode metacercariae; negative effect) were also important. The consistent, broad spatial gradients in overwinter survival observed in this study can help guide efforts designed to enhance coho salmon production in coastal Streams and suggest that habitat protection, restoration, and enhancement strategies will be best guided by a whole-basin context.
Accepted: 26 Jan 2009

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