The first document provides an interim report on the joint efforts of PATH scientists to assess the responses of ESA-listed Snake River spring/summer chinook to various hydrosystem actions being considered by the region. This work builds on previous PATH analyses of historical data published in the PATH Final Report on Retrospective Analyses for Fiscal Year 1996, and applies a formal decision analysis approach, a method for evaluating management actions when there are different points of view about the probable outcomes of those actions.

Over the past year, the PATH group has made considerable progress in agreeing on common data sets and assumptions. However, gaps in historical data and understanding result in remaining uncertainties. Therefore, a major component of the report is the description of the uncertainties that may affect future trends in salmon populations, and analyses to identify which of these uncertainties have the most influence on the relative performance of different management actions. The next step in this process, and yet to be completed, is to formally assess the relative support for alternative points of view and thereby clarify recommendations to decision-makers. The authors caution, however, that in some cases the lack of evidence will not allow definitive assessments on the relative likelihood of each point of view. As several of the reviewers have noted, well-planned experimental management actions may be the only way to resolve these uncertainties. PATH has begun to explore possibilities for an experimental management approach.

For the next four months, PATH intends to focus on completing analyses for fall chinook. Work on spring/summer chinook will resume in July, with a final report for spring/summer chinook scheduled for completion by the fall of 1998. The final report will include the results of the weight of evidence approach, along with analyses of additional hypotheses and management actions (e.g. John Day drawdown).