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4. Resident fish mitigation


For resident fish and other aquatic species impacted by the hydrosystem, protect and mitigate freshwater and associated terrestrial habitat, and native fish populations.


Mitigation is required for native resident fish and other freshwater species impacted by the construction and operation of the hydropower system. Native resident fish and other freshwater species addressed in this strategy include freshwater mussels, threatened bull trout, burbot, westslope cutthroat trout, mountain whitefish, endangered Kootenai white sturgeon, and resident life histories of the native anadromous species, such as Columbia River white sturgeon and kokanee. Impacts have resulted in losses to abundance, genetic diversity, life history diversity, spatial diversity and movements of these species, as well as modification of their habitat resulting from inundation. The program recognizes the importance of all native resident fish and other freshwater species, in maintaining ecosystem diversity and function, and contributing to cultural aspects in the basin. It relies on a diversity of strategies to address those losses, including habitat mitigation, hatcheries, harvest augmentation, and modifying hydrosystem operations.


  • Apply a diversified approach for mitigating losses, including hatcheries, harvest augmentation, modifying hydrosystem operations, and habitat mitigation that involves habitat protection to protect habitat for native fish in-perpetuity and as a tool to mitigate for lost habitat
  • Conduct research to identify and determine how to resolve limiting factors, and apply a prioritized approach for addressing limiting factors within a watershed.
  • In areas of the Columbia River Basin that have quantitative native resident fish loss assessments in terms of acres or stream miles of key habitat inundated or blocked, these losses may be most effectively mitigated by acquiring interests in real property for the purpose of preserving and enhancing fish habitat equal to the quality of habitat lost. In such cases, acquire and maintain land in perpetuity for purposes of fish habitat, at a minimum ratio of 1:1 mitigation to lost distance or area. Focus land acquisitions on parcels with connectivity and intact healthy riparian and stream habitat as these will improve fish habitat resiliency [see guidance for resident fish settlements for details]. Whenever possible, resident fish mitigation via habitat acquisitions should take place through long-term settlement agreements similar to those described above for wildlife mitigation agreements. Currently resident fish loss assessments exist for Libby and Hungry Horse dams.
  • Consider the following guidance when addressing resident fish losses related to the development and operation of the hydropower system:
    • Address weak, but recoverable, native populations injured by the hydropower system, as such populations are identified for the Council by the fishery agencies and tribes.
    • Address areas of the basin where anadromous fish are not present.
    • Implement resident fish projects that also provide benefits for wildlife.
    • Enhance populations that support important fisheries.

General measures

  • Where feasible, Bonneville shall preserve, enhance, and restore native fish in native habitats.
  • Bonneville shall develop interim fisheries where native fisheries have been lost, or where native populations and habitats are actively being recovered, and need protection.
  • In areas where losses may be most effectively mitigated by acquiring interests in real property, Bonneville shall acquire fish habitat equal to the quality of habitat lost through the acquisition of appropriate interests in real property at a minimum ratio of 1:1 mitigation to lost distance or area [see guidance for resident fish settlements].
  • The Council will convene a work group of fish and wildlife agencies and tribes, and Bonneville, to develop a standardized methodology for habitat loss assessments to assist areas that currently do not have the capacity to complete this assessment and do not have a mitigation settlement agreement, and to ensure a consistent level of accuracy across the basin. This task force shall consider past efforts[1] and will report to the Council quarterly on its progress toward developing a methodology.
  • Once loss assessments are completed and adopted by the Council, the Council encourages Bonneville to negotiate settlement agreements, as described in Appendix K.
  • Bonneville shall continue to support projects directed at other native freshwater species and the progression of these projects from a research and assessment phase into a restoration and monitoring phase
  • Bonneville shall support efforts to address all limiting factors affecting resident fish. This might include efforts to eradicate and suppress non-native species, research on critical uncertainties, impacts from ongoing operation of the hydrosystem, and other impacts.
  • Bonneville shall support evaluating the size of non-native fish populations to determine the potential effect of predation and implement a predator management program where appropriate in the Columbia Basin, for example Lake Roosevelt.
  • Bonneville, the Corps, and the Bureau shall restore passage for native resident fish where feasible, including at Albeni Falls Dam.

Link to subbasin plans

See the Council’s subbasin plans for subbasin-level information pertaining to resident fish mitigation.

Links within the program

Strategies: habitat, ecosystem function, non-native and invasive species, climate change.

[1] Consider building from the 2009 draft inundation methodology developed by the CBFWA Resident Fish Advisory Committee. Additional draft technical documents.

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