Introduction
Management controls for Snake River fall chinook salmon can be grouped into four broad categories: (1) improving production; (2) improving downstream passage of smolts; (3) reducing harvest; and (4) improving upstream passage of returning adults. Current modeling efforts to analyze recovery strategies utilize downstream passage and life-cycle models to predict the effects of a relatively narrow range of management options that often include several specific actions within each of the four categories mentioned above. This approach often makes it difficult to see the bigger picture. Clearly, improvements in any one of the four categories reduces the need for improvements in the other three. Before selecting options within each category, it would seem prudent to first decide how much each category should, and can, contribute to the overall solution. I suggest that the decision-making process should proceed in two steps: (1) set improvement goals for each category; and (2) determine specific tactics for reaching each goal. This approach will help stakeholders understand their relative contribution to the overall recovery effort and will focus modeling efforts on more specific problems within categories.
This report has two goals: (1) describe a simple spreadsheet model that encompasses all of the major life history stages of chinook salmon; and (2) use the model to define an overall solution space in terms of three of the four control variables (downstream survival, harvest, and upstream passage). The results are presented in a single graph that illustrates all possible solutions to reaching a specific escapement goal, in this case set at 3,000 spawners in year 2017. For example, the model indicates that improving downstream survival 36%, reducing harvest by 60%, and improving upstream survival to 90% is equivalent to improving downstream survival by 360%, reducing harvest by 30%, and making no improvements in upstream survival.