Fraser River sockeye salmon: data synthesis and cumulative impacts

will likely have a high correlation (e.g., internet usage in the City of Vancouver has likelyincreased substantially and consistently since the early 1990s, corresponding directly to theperiod over which there have been substantial declines observed in the productivity of FraserRiver sockeye salmon).We performed a second analysis with one additional stressor category – the abundance of pinksalmon both in the Northeast Pacific and from Russia. The analysis was extended to include pinksalmon for two reasons: 1) the PSC Report found evidence for competitive effects of pinksalmon on Fraser sockeye (section 4.9 in Peterman et al., 2010); and 2) the data were madeavailable to us. The PSC report examined three potential mechanisms by which pink salmonmight affect Fraser sockeye, and rejected two of these due to contradictory evidence. Theremaining hypothesis is that abundant odd-year pink salmon from Alaska and Russia competewith adult Fraser sockeye on the high seas, which is consistent with the observation that Frasersockeye spawning in odd years show poorer growth & survival than even-year Fraser sockeye.The results from this set of analyses show that the pink salmon model (M8) and the global model(M1) appear as the strongest two models. The level of support for both of these models is similarbut because they are substantially different models, the interpretation is that they providelegitimately competing models to explain the patterns observed in Fraser River sockeye salmon.The predators/alternate prey model (M5) is third, but with a lower level of support. The fact thatthe pink salmon model does well is in some ways not surprising: there is a scientificallysupported hypothesis, with good data for the attribute that the hypothesis relates to, and theconnection is specific to a life history stage.4.8 Other Potential Factors Not Included in Cohen CommissionThe projects comprising the Cohen Commission’s Scientific and Technical Research Programrepresent an extensive but not exhaustive coverage of potential factors that may have contributedto the decline of Fraser River sockeye salmon. Table 4.8-1 lists some additional theories andpotential factors that have not been explicitly included within the scope of the CohenCommission technical reports, or this report. These additional, potentially contributing factorsare presented here simply to acknowledge that other theories do exist, beyond the scope of theCohen Commission and beyond the scope of the present report. The analyses conducted withinthis project do not (and could not) exhaustively represent all possible factors.99