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Modeling Climate and Hydropower Influences on the Movement Decisions of an Anadromous Species

Summary

Steelhead salmon in the Columbia River face threats from warming waters and dams that interrupt their journeys home to spawn. Scientists analyzed 20 years of tracking data to understand how temperature and dam operations affect where these fish go during migration. They found that warmer temperatures make fish less likely to reach their home streams, but dam managers might be able to help by releasing water at strategic times. This research shows that fighting climate change will require both natural ecosystem recovery and smarter management of hydroelectric dams.

Background

The Columbia River Basin supports threatened Pacific salmon populations that face combined stressors from climate change and hydropower development. Steelhead (Oncorhynchus mykiss), an anadromous species with complex life histories, are particularly vulnerable to rising temperatures and dam operations during their adult pre-spawn migration. Understanding how these stressors interact is critical for developing effective management strategies.

Objective

To model the effects of temperature and hydropower operations on adult Steelhead movement decisions during pre-spawn migration using 20 years of PIT-tagging data. The study aimed to predict homing success to natal tributaries under different climate and hydropower management scenarios and assess the relative importance of each factor for population recovery.

Results

Temperature consistently negatively influenced natal homing probability and positively influenced natal tributary overshoot and non-natal tributary use across populations. Evidence for population-specific benefits of winter spill on homing success was found, particularly for Walla Walla and Tucannon River populations. Simulations under warmer temperature scenarios showed decreased homing probabilities across all populations.

Conclusion

Rising temperatures threaten Steelhead survival through increased deleterious movement behaviors and interactions with hydroelectric dams. Hydropower managers may partially offset climate impacts through strategic spill management, but additional studies are needed to determine efficacy. The integrated modeling approach successfully demonstrates how combining climate and management factors can inform species recovery strategies.
  • Published in:Global Change Biology,
  • Study Type:Statistical Modeling Study,
  • Source: PMID: 41045009
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