Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7541
Title: Increasing hydrologic variability threatens depleted anadromous fish populations
Author: E. J. Ward, J. H. Anderson, T. J. Beechie, G. R. Pess, Michael J. Ford
Publication Year: 2015
Journal: Global Change Biology
Keywords: climate change,flow,Puget Sound,Chinook salmon,variability,population dynamics,

 Predicting effects of climate change on species and ecosystems depends on understanding responses to shifts in means (such as trends in global temperatures), but also shifts in climate variability. To evaluate potential responses of anadromous fish populations to an increasingly variable environment, we performed a hierarchical analysis of 21 Chinook salmon populations from the Pacific Northwest, examining support for changes in river flows and flow variability on population growth. More than half of the rivers analyzed have already experienced significant increases in flow variability over the last 60 years, and this study shows that this increase in variability in freshwater flows has a more negative effect than any other climate signal included in our model. Climate change models predict that this region will experience warmer winters and more variable flows, which may limit the ability of these populations to recover.