James J. Anderson and Richard W. Zabel
Columbia Basin Research
University of Washington
Box 358218
Seattle, WA 98195
Richard A. Hinrichsen
Hinrichsen Fisheries Consulting
Lakeview Medical Dental Building
3216 NE 45th Pl Suite 303W
Seattle WA 98105
January 12, 2000
The purpose of this study is to model the effect of a John Day Reservoir drawdown on anadromous salmonid populations, particularly populations listed under the Endangered Species Act. The approach utilizes passage models to characterize smolt survival through the hydrosystem and incorporates the passage model results into life-cycle models to characterize the effects of John Day actions on adult population levels. Because significant uncertainties exist on the effect of mitigation actions on fish survival and on how observed survivals are partitioned throughout the life cycle, a number of hypotheses are included in the analysis. The goal is to characterize the average effects over a range of hypotheses and to demonstrate the range of effects resulting from different hypotheses.
To produce estimates of the impacts of John Day mitigation actions on adult population levels, this analysis has used three methods. First of all, we utilized methods and results produced by PATH (Plan for Analyzing Testable Hypotheses, a group of approximately 25 scientists from state, tribal and federal agencies). The outputs from the PATH analysis are probabilities of meeting survival and recovery standards, and results relevant to this study are reported. Second, we simplified the PATH analysis (by removing the Bayesian decision analysis framework) to produce mean equilibrium spawner levels for particular actions under a range of hypotheses. This method produces intuitive results and can be used to estimate the gain or loss of spawning adults when analyzing one action compared to another. Third, for the more detailed analyses of actions at the John Day project, we further simplified the life-cycle analyses to produce only the difference in spawner levels under two actions. This simplification arises from the assumption that actions taken at the John Day project will not affect survivals in other life stages (e.g., ocean survival or egg to smolt survival) with the result that these survivals will cancel out when comparing two actions.
The specific actions considered at the John Day project were reservoir drawdown to natural river level, reservoir drawdown to the spillway crest, and drawdown to natural river level but using John Day pool as a storage reservoir for flood control under high flow conditions. The analysis of the direct impacts of these actions on the survival of migrating smolts was conducted using the Columbia River Salmon Passage (CRiSP) model, developed at the University of Washington. In addition results from the FLUSH model (Fish Leaving under Several Hypotheses, developed by state and tribal agencies) were incorporated into life-cycle analyses where available.
For this report, Snake River spring and fall chinook were analyzed. Both these stocks are listed as threatened under the Endangered Species Act and were the focus of the PATH analysis. In addition, Hanford Reach fall chinook and Upper Columbia spring chinook were evaluated.
To summarize, three model systems were applied in the analysis. The PATH Bayesian life-cycle model to estimate the probabilities of survival and recovery, a deterministic model to determine the equilibrium and maximum sustainable spawner populations, and the CRiSP passage model to evaluate the impacts of drawdown on smolt survival and fish travel time.