Fraser River sockeye salmon: data synthesis and cumulative impacts

data are insufficient to perform any systematic assessment of these hypotheses. Miller et al.(2010, presentation at June 2010 PSC Workshop) found that sockeye smolts contained a genomicsignal indicative of physiological stress prior to entering the ocean, which she attributed to stressin freshwater. However, the genomic signal detected by Miller et al. was present in smolts duringboth 2007 and 2008 (Miller, handout provided to June 2010 PSC Workshop), yet those years ofentry apparently had very different marine survival rates (based on the very large difference inobserved vs expected adult returns in 2009 vs. 2010).4.2.4 Correlation/consistency with patterns in non-Fraser River sockeyeproductivityThe Cohen Commission studies did not include assembly of data on potential stressors forsockeye stocks outside of the Fraser Basin. Therefore we cannot quantitatively analyze the levelof correlation of stressors with productivity trends in non-Fraser stocks. However, we can makesome qualitative arguments, admittedly speculative regarding the consistency of hypothesizedstressors with observed productivity declines. First, it is very likely that freshwater habitatconditions (including contaminants) vary greatly across the 64 stocks analyzed by Peterman andDorner (2011), yet most of these stocks show broadly similar patterns of decline. Second, it isvery likely that most non-Fraser stocks on the central and north coast of B.C, and in SE Alaskahave equal or better habitat conditions than most watersheds in the Fraser Basin, simply based onpopulation density. Third, with increasing efforts at regulation of land use activities and habitatrestoration over the last two decades, salmon habitats in most non-Fraser watersheds are likely tohave shown less degradation than in prior decades with less regulation. Therefore, ourexpectation is that it is unlikely that habitat conditions would be correlated with decliningproductivity in most of the non-Fraser stocks. However, given the absence of any exposure dataand correlation analyses for these stocks, no rigorous conclusion is possible.Peterman et al. (2010; Section 4.7) noted that stocks outside of the Fraser Basin usually do nothave such strong and regular fluctuations in abundance; they therefore concluded that delayeddensity dependence was not a likely mechanism for observed declines in non-Fraser sockeyestocks. Peterman and Dorner (2011; Tables 2 and 3, Appendix P2) looked at 46 non-Frasersockeye stocks. They examined the level of support in the data for two spawner-recruit models:the Ricker model (without delayed density dependence), and the Larkin model (with delayeddensity dependence). While the Larkin model had more support than the Ricker model in 10 outof 46 non-Fraser stocks, the results indicate that the declines in these non-Fraser stocks were notcaused by over-escapement, for two reasons (B. Dorner, pers. comm.). First, there are not thatmany cases where spawner abundance was unusually high over the period of decliningproductivity. Second, in the cases where there were years with unusually high spawner46