Fraser River sockeye salmon: data synthesis and cumulative impacts

additional analyses to gain further evidence about likely agents as causes of observed harm”,which precisely describes the challenge of the present project as well.The WOE approach to retrospective ecological risk assessment that we have utilized challengesthe available evidence for each potential factor with the same sequential set of questions asemployed by Burkhardt-Holm and Scheurer (2007) in their evaluation of the decline of browntrout in Swiss rivers, though we have grouped several questions into one step. One of ourchallenges is that we are applying this approach retrospectively to a series of projects thatthemselves did not utilize a formal RERA framework. We cannot answer questions that were notasked in the projects themselves. Within each life stage we examine the major potential causativeagents identified within the other Cohen Commission Technical Reports. For each factor, wesynthesize the evidence by addressing the following questions:1. Plausible mechanism:“Does the proposed causal relationship make sense logically and scientifically?”2. Exposure:“Is there evidence that sockeye populations are, or have been, exposed to the causalfactor?3. Correlation/Consistency:“Is there evidence for association between adverse effects in sockeye populations andpresence of the causal factor, either in time or space?”4. Other Evidence:Is there further evidence available to support the likelihood of that a factor has made asubstantial contribution, such as answers to the questions below?Thresholds:“Do the measured or predicted exposure levels exceed qualitycriteria or biologically meaningful thresholds?”Specificity:“Is there an effect in the population known to be specificallycaused by exposure to the stressor?”Experiments: “Have the results from controlled experiments in the field orlaboratory led to similar effects?”Removal:effects in the population?”“Has the removal of the stressor led to an amelioration of theWithin each step of this evaluation, we emphasize both what is known and what is not known,and within each life stage we identify the key things that need to be known better. WithinQuestion 3, we synthesize the evidence on any relationship with observed patterns in Fraser22