Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7488
Title: Signals of climate, density-dependence, and human disturbance in Pacific salmon dispersal
Author: Peter A.H. Westley, Andrew H. Dittman, E. J. Ward, T. Quinn
Publication Year: 2015
Journal: Ecology
Keywords: Pacific salmon,straying,Metapopulation,climate,Density dependence,

 Dispersal is the foundational process underpinning adaptive climate-induced range shifts, yet is widely assumed to be insensitive to climatic or human disturbances. Using a 17-year database representing 159,719 Chinook salmon marked as juveniles from 19 hatchery populations in the Columbia River, USA, and recovered as adults throughout the basin, we show that 86.3% of the interannual deviance in dispersal rate can be explained by abiotic, biotic, and human variables. We detected a net negative influence of i) the Pacific Decadal Oscillation climatic index, ii) density-dependence, iii) discrepancies in the magnitude of stream flow during outmigration and return years, and iv) hatchery practices that potentially disrupt the imprinting process as juveniles. In contrast, we detected a net positive influence of increasing water temperature on stray rates. For other factors we revealed significant responses by subsets of populations, despite no net effects. Taken together these results challenge the pervasive assumption that dispersal rates are homogenous within species, temporally static, and insensitive to climatic forcing.