Fraser River sockeye salmon: data synthesis and cumulative impacts

Figure A3.5-1. Flow diagram used to assign the relative likelihood that a particular factor has made a substantialcontribution to the decline of Fraser River sockeye salmon, based on the answers to the questions used tochallenge the available evidence. This structure is adapted from Burkhardt-Holm and Scheurer (2007,Figure 1).Because this method is an inherently retrospective form of analysis, the results cannot be used topredict the impacts that these factors may have in the future. Both Forbes and Callow (2002) andBurkhardt-Holm and Scheurer (2007) emphasize that it is unrealistic to expect these methods tobe definitive in terms of ascribing causation. While such an approach may be able to explainretrospectively which factors most likely contributed to past patterns of change in productivity,the importance of particular factors may be more or less important in the future and will varywithin any given year in both magnitude and relative importance. Even if we had complete dataon all of the factors potentially affecting sockeye over the entire period of record for the stockproductivity data, we would not be able to predict in advance how these factors will combine inthe future to affect productivity.200