1 DECADAL SCALE CLIMATE PATTERN AND SALMON SURVIVAL: INDICATORS, INTERACTIONS AND IMPLICATIONS James J. Anderson School of Fisheries University of Washington, Seattle WA ABSTRACT The influence of decadal scale climatic variations on the decline of Columbia River salmon was not realized until recently. I evaluate the implications of this omission using a stock recruitment model with climatic and anthropogenic factors. I conclude that fisheries managers over the past century have misinterpreted the anthropogenic impacts on Columbia River salmon. In particular, I suggest three major events have been misinterpreted: 1) managers overestimated the significance of harvest on the catch decline after 1920 by not accounting for climatic changes that lowered ocean survival at this time, 2) managers under -represented the detrimental effects of the hydrosystem by not accounting for the contribution of good ocean survival during the years of hydrosystem development and, 3) managers underestimated the success of stock rebuilding measures in the last two decades because the concomitant poor ocean survival was not accounted for. I also suggest that the fisheries community is now evolving an ecosystem approach that considers both environmental and anthropogenic impacts on salmon. Introduction Over this century management strategies have been unsuccessful in halting the salmon decline in the Columbia River system. Through the failures, an understanding of the processes affecting the fishery has evolved an ecosystem perspective in which both anthropogenic and natural factors are considered. In this paper I illustrate how this history has evolved using a stock-recruitment model that represents the assumptions and projections through three management periods, each one an adaptive management experiment with unique problems and a management paradigm. In recent years this cycle has been coined adaptive management, where learning is achieved through management actions (Lee 1995). Adaptive management involves a number of basic steps outlined in Figure 1. An action taken on a resource is based on a prior prediction of its effect. The actual effect is monitored, either by exploitation of the resource or through a specific monitoring program, and the results are evaluated through comparison with the prior prediction. Discrepancies between the predicted and observed effects are used to modify the To appear in the NMFS Workshop on Estuaries and Ocean Survival of Salmon, held in Newport Oregon, March 1996