Fraser River sockeye salmon: data synthesis and cumulative impacts

declines (discussed in section 4.2 for life stage 1) reflects the net effect across all life historystages. Aquaculture was not considered in our report as the Commission Technical reports onthis potential stressor were not available, but will be considered in an addendum to this report.Table 4.5-1. Evaluation of the relative likelihood that potential stressors encountered by Fraser River sockeyesalmon during their growth and maturation in the ocean and return to the Fraser River (Stage 4) havecontributed to overall declines in productivity in recent decades. See section 4.7 for further statisticalanalyses relevant to the correlation/consistency column.Factor Mechanism Exposure Correlation/Consistency Other LikelihoodEvidencePathogens Yes No data - - NoconclusionpossiblePredators Yes Yes No data No data PossibleMarine Yes Yes Yes No data PossibleConditionsHuman Yes No - - UnlikelyActivities andDevelopment(Sog)ClimateChangeYes Yes Yes No data Possible4.5.7 Key things we need to know betterThere are several elements about the life history of Fraser River sockeye salmon that are poorlyunderstood and inhibit a better understanding of the contribution of key stressors in this life stageto the overall decline in the population.1. estimates of the abundance of sockeye salmon reaching the Gulf of Alaska would helpdistinguish mortality occurring during the open ocean phase from mortality potentiallyoccurring earlier prior to leaving the continental shelf.2. information on the health and condition of sockeye salmon reaching the Gulf of Alaska,including size, contaminant and disease burdens, signs of temperature stress, wouldprovide valuable insight into whether the population is in such poor condition that itwould be vulnerable to even moderate stresses or in such good condition that it wouldrequire stressors with very substantial impacts to affect the population in this stage.3. better understanding of the spatial and temporal distribution of sockeye salmon in theGulf of Alaska would guide researchers on where to focus greater attention while lookingfor potential changes in ocean conditions, predators, etc.79