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Article
Factors Influencing the Survival of Outmigrating Juvenile Salmonids Through Multiple Dam Passages: An Individual-Based Approach
Ecology and Evolution
  • Timothy Elder, Portland State University
  • Christa M. Woodley, US Army Engineer Research and Development Center
  • Mark A. Weiland, Pacific Northwest National Laboratory
  • Angela L. Strecker, Portland State University
Document Type
Article
Publication Date
7-1-2016
Subjects
  • Chinook salmon,
  • Chinook salmon -- Migration -- Columbia River Watershed,
  • Anadromous fishes -- Columbia River Watershed
Abstract

Substantial declines of Pacific salmon populations have occurred over the past several decades related to large-scale anthropogenic and climatic changes in freshwater and marine environments. In the Columbia River Basin, migrating juvenile salmonids may pass as many as eight large-scale hydropower projects before reaching the ocean; however, the cumulative effects of multiple dam passages are largely unknown. Using acoustic transmitters and an extensive system of hydrophone arrays in the Lower Columbia River, we calculated the survival of yearling Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) passing one, two, or three dams. We applied a unique index of biological characteristics and environmental exposures, experienced by each fish individually as it migrated downstream, in order to examine which factors most influence salmonid survival. High outflow volumes led to involuntary spill in 2011 and created an environment of supersaturated dissolved gas concentrations. In this environment, migrating smolt survival was strongly influenced by barometric pressure, fish velocity, and water temperature. The effect of these variables on survival was compounded by multiple dam passages compared to fish passing a single dam. Despite spatial isolation between dams in the Lower Columbia River hydrosystem, migrating smolt appear to experience cumulative effects akin to a press disturbance. In general, Chinook salmon and steelhead respond similarly in terms of survival rates and responses to altered environmental conditions. Management actions that limit dissolved gas concentrations in years of high flow will benefit migrating salmonids at this life stage.

Description

© 2016 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Originally published in Ecology and Evolution and can be found online at: https://doi.org/10.1002/ece3.2326

DOI
10.1002/ece3.2326
Persistent Identifier
http://archives.pdx.edu/ds/psu/18550
Citation Information
Elder, T., Woodley, C. M., Weiland, M. A. and Strecker, A. L. (2016), Factors influencing the survival of outmigrating juvenile salmonids through multiple dam passages: an individual-based approach. Ecol Evol, 6: 5881–5892.