Fraser River sockeye salmon: data synthesis and cumulative impacts

feel reasonably confident in this conclusion because juvenile productivity (which integrates allstressors in this life history stages) has not declined over time in the eight of the nine Frasersockeye stocks where it has been measured. We would be even more confident if more stockshad smolt enumeration rather than fry estimates (only Chilko and Cultus stocks have smoltestimates). Though not primary drivers of the Fraser sockeye situation, each of these factors maystill have had some effects on some Fraser stocks in some years (the data are insufficient to rejectthat possibility). We suspect, based on qualitative arguments alone, that habitat and contaminantinfluences on Life Stage 1 were also not the primary drivers responsible for productivity declinesoccurring to most non-Fraser stocks assessed by Peterman and Dorner (2011). However, giventhe absence of any exposure data and correlation analyses for non-Fraser stocks, it is not possibleto make conclusions on the relative likelihoods of factors causing declining productivities innon-Fraser stocks.None of the factors considered in this section is likely to have been much worse in 2005 and2006 for Fraser sockeye stocks, sufficient to have significantly decreased egg-to-smolt survivalin the salmon that returned in 2009. Similarly, none of these factors is likely to have been muchbetter in 2006 and 2007, sufficient to have substantially improved egg-to-smolt survival in thesalmon that returned in 2010.4.2.7 Key things we need to know betterThe various scientists working on projects for the Cohen Commission completed their analysesto the greatest degree possible given the limitations of data and time. The above conclusions,while reliable given the diverse lines of evidence, are nevertheless constrained by serious datagaps. For the spawning and rearing phase of sockeye life history, some of the critical needs forbetter data and understanding include:1. increased numbers of stocks with quantitative assessments of smolt outputs andcondition (currently only available for Chilko and Cultus lakes), to distinguish survivalrates in pre and post-juvenile life stages and evaluate the likelihood of alternativehypotheses, and for these same stocks;2. better estimates of both watershed and in-lake conditions over time (including thecumulative effects of multiple stressors) using consistent methods, for a cross-section ofstocks with varying conditions (e.g., migration distance, levels and types of watersheddisturbance), to better understand current status, causative mechanisms and riskthresholds;3. better understanding of the status of smaller conservation units, consistent withimplementation of the Wild Salmon Policy; and49