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Fraser River sockeye salmon: data synthesis and cumulative impacts

Fraser River sockeye salmon: data synthesis and cumulative impacts

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A4.3.2Model: A4cBrood years: 1969-2001Analyses by life stageA model set was tested with the available <strong>data</strong> for brood years 1969-2001. The list of potentialvariables provided by the Cohen Contractors is not exhaustive (i.e., other important variablesmay exist, or <strong>data</strong> may not have been available). However, for this time period there are at least afew variables for all but two life stages: incubation-rearing <strong>and</strong> spawning. There are a total of 33potential stressor variables. While there are 611 records in this time period, there are only 463observations of ln(R/S) with complete <strong>data</strong>. Two stocks: Harrison <strong>and</strong> Cultus, have no <strong>data</strong> forone stressor variable (Water Quality during outmigration) in this time period <strong>and</strong> are notincluded in this analysis. Each stressor was linked to a particular life stage as described inAppendix A3-4 Data Preparation). In some cases the same <strong>data</strong> may be linked to several lifestages (e.g., predators could potentially impact <strong>sockeye</strong> during their inshore migration or duringtheir return migration to spawn). Table A4.3-3 describes the ten different models in this modelset, Table A4.3-4 shows the relative fit of each model, <strong>and</strong> Table A4.3-5 provides the estimatesfor each parameter <strong>and</strong> model.Table A4.3-3. Model descriptions for model set A4c (comparison among life stages for brood years 1969-2001).ModelNameModel descriptionNumber ofstressorsTotal number ofparametersM1 Global model: contains variables associated 31 50with all life stages.M2 Life stage 1: Incubation-rearing. 0 19M3 Life stage 2: Smolt Outmigration 6 25M4 Life stage 3: Inshore Migration <strong>and</strong> 13 32Migration to Rearing AreasM5 Life stage 4a: Growth in North Pacific 2 21M6 Life stage 4b: Return to <strong>Fraser</strong> 8 26M7 Life stage 5a: Return to spawn (upstream 4 23migration) 26M8 Life stage 5b: Spawning 0 19M9 All freshwater life stages: 1, 2, 5a, <strong>and</strong> 5b 7 26M10 All marine life stages: 3, 4a, <strong>and</strong> 4b 23 4126 Note: the response variable used in the analysis, ln(R/S) already incorporates en-route mortality <strong>and</strong> so thishypothesis refers to any delayed effect on productivity (e.g., spawners may not produce as many offspring if they arestressed) resulting from the upstream migration.237

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