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Evolutionary and Ecological Connectivity in Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) and Mountain Whitefish (Prosopium williamsoni) in Relation to the Potential Influences of Boundary Dam, Washington, Idaho, and Parts of British Columbia

Open-File Report 2022-1084
Prepared in cooperation with the University of British Columbia, Biodiversity Research Centre and Beaty Biodiversity Museum, and Idaho State University, Department of Biological Sciences, Fish Ecology Laboratory
By: , , and 
https://doi.org/10.3133/ofr20221084

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Abstract

In this report, we consider evolutionary and ecological connectivity for westslope cutthroat trout (Oncorhynchus clarkii lewisi) and mountain whitefish (Prosopium williamsoni) within the Pend Oreille River in northeastern Washington State, northern Idaho, and adjacent portions of southeastern British Columbia, Canada. Specifically, we focused on the rationale for active translocation of individuals of these species upstream from Boundary Dam both in the context of natural patterns of pre-dam evolutionary connectivity as well as preserving contemporary ecological and evolutionary characteristics of local extant populations. Boundary Dam impounds the Pend Oreille River (called the Pend d’Oreille River in Canada) with the resulting reservoir inundating two historical barriers to upstream movement of fish (Metaline Falls and Z Canyon). Historically, it was thought these barriers impeded the upstream movement of westslope cutthroat trout and mountain whitefish, as well as Pacific salmon (Oncorhynchus spp.), steelhead trout (O. mykiss), and other resident species such as bull trout (Salvelinus confluentus). To address connectivity, we consider historical and contemporary processes and features. This review includes an assessment of postglacial processes within the Pend Oreille River and systems upstream that include Priest Lake, Lake Pend Oreille, the Clark Fork River, features of Boundary Reservoir and its tributaries, and areas downstream in the Pend Oreille River such as the Salmo River. Based on this information, we then give a more detailed review of existing genetic and ecological data to summarize what is known about connectivity for westslope cutthroat trout and mountain whitefish. Our assessment of the collective evidence leads us to conclude that moving fish upstream over Boundary Dam is not warranted if the management objective is to maintain natural patterns of evolutionary and ecological connectivity or to conserve unique ecological and evolutionary characteristics of extant local populations of these species in the system. These findings parallel that of a previous analysis of bull trout. Although we were able to arrive at well-supported conclusions in relation to Boundary Dam, we suggest that more work on connectivity further upstream in the Pend Oreille River would help to better understand the role of historical processes and dams further up in the system.

Suggested Citation

Dunham, J.B., Taylor, E.B., and Keeley, E.R., 2022, Evolutionary and ecological connectivity in westslope cutthroat trout (Oncorhynchus clarkii lewisi) and mountain whitefish (Prosopium williamsoni) in relation to the potential influences of Boundary Dam, Washington, Idaho, and parts of British Columbia: U.S. Geological Survey Open-File Report 2022–1084, 22 p., https://doi.org/10.3133/ofr20221084.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Part 1. Lake Pend Oreille and Pend Oreille River—Past to 2022
  • Part 2. Evolutionary and Ecological Connectivity for Westslope Cutthroat Trout and Mountain Whitefish
  • Part 3. Conclusions and Recommendations for Upstream Passage over Boundary Dam
  • Overall Conclusions
  • References Cited
  • Appendix 1. Summary and Update on Connectivity for Bull Trout (Salvelinus confluentus) in the Pend Oreille River since Dunham and Others (2014)
Publication type Report
Publication Subtype USGS Numbered Series
Title Evolutionary and ecological connectivity in westslope cutthroat trout (Oncorhynchus clarkii lewisi) and mountain whitefish (Prosopium williamsoni) in relation to the potential influences of Boundary Dam, Washington, Idaho, and parts of British Columbia
Series title Open-File Report
Series number 2022-1084
DOI 10.3133/ofr20221084
Year Published 2022
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description vii, 22 p.
Country Canada, United States
State British Columbia, Idaho, Washington
Other Geospatial Boundary Dam
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details