Variability in expression of anadromy by female Oncorhynchus mykiss within a river network

Environmental Biology of Fishes
By: , and 



We described and predicted spatial variation in marine migration (anadromy) of female Oncorhynchus mykiss in the John Day River watershed, Oregon. We collected 149 juvenile O. mykiss across 72 sites and identified locations used by anadromous females by assigning maternal origin (anadromous versus non-anadromous) to each juvenile. These assignments used comparisons of strontium to calcium ratios in otolith primordia and freshwater growth regions to indicate maternal origin. We used logistic regression to predict probability of anadromy in relation to mean annual stream runoff using data from a subset of individuals. This model correctly predicted anadromy in a second sample of individuals with a moderate level of accuracy (e.g., 68% correctly predicted with a 0.5 classification threshold). Residuals from the models were not spatially autocorrelated, suggesting that remaining variability in the expression of anadromy was due to localized influences, as opposed to broad-scale gradients unrelated to mean annual stream runoff. These results are important for the management of O. mykiss because anadromous individuals (steelhead) within the John Day River watershed are listed as a threatened species, and it is difficult to discern juvenile steelhead from non-anadromous individuals (rainbow trout) in the field. Our results provide a broad-scale description and prediction of locations supporting anadromy, and new insight for habitat restoration, monitoring, and research to better manage and understand the expression of anadromy in O. mykiss.

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Publication type Article
Publication Subtype Journal Article
Title Variability in expression of anadromy by female Oncorhynchus mykiss within a river network
Series title Environmental Biology of Fishes
DOI 10.1007/s10641-011-9946-4
Volume 93
Issue 4
Year Published 2012
Language English
Publisher Springer
Publisher location Reston, VA
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description 13 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Environmental Biology of Fishes
First page 505
Last page 517
Country United States
State Oregon
Other Geospatial John Day River
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