Body Size and Growth Rate Influence Emigration Timing of Oncorhynchus mykiss Public Deposited

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  • Juvenile Oncorhynchus mykiss migrate extensively in freshwater during fall. We used individual tagging to study the spatial origin, influences, and outcomes of fall migration on fish that emigrated from summer rearing tributaries during fall (early-emigrants) and those that did not (late-emigrants) in the South Fork John Day River, Oregon. Fall migration amplified body size differences between early and late-emigrants. There were more early-emigrants from a lower gradient stream than from a higher gradient stream. Early-emigration was positively related to individual summer growth rate and fall body size. Oncorhynchus mykiss dispersed downstream into higher order streams during fall. Early-emigrants shifted to an alternative location and experienced significantly greater winter growth compared to late-emigrants that remained in tributaries. Early-emigrants initiated smolt migration sooner the following spring than late-emigrants. Early and late-emigration from the South Fork John Day was associated with asynchronous emigrant-to-adult survival rates.
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  • Ian A. Tattam , James R. Ruzycki , Hiram W. Li & Guillermo R. Giannico (2013) Body Size and Growth Rate Influence Emigration Timing of Oncorhynchus mykiss , Transactions of the American Fisheries Society, 142:5, 1406-1414, DOI:10.1080/00028487.2013.815661
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  • 142
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  • 5
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  • The work of I. Tattam., H. Li, and G. Giannico was funded by the U.S. Bureau of Reclamation, Pacific Northwest Region through M. Newsom. The involvement of J. Ruzycki was supported by the Bonneville Power Administration (Project Number 1998-016-00) through J. Baugher, J. Karnezis, and J. Swan.
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