Fraser River sockeye salmon: data synthesis and cumulative impacts

A4.3.4Analysis by regionModel: C4a1969-2004A model set was tested with the available data for brood years 1969-2004, which includedvariables for sea surface salinity (SSS), discharge and wind for QCS, and sea surface temperature(SST), SSS and discharge for SoG. While temperature is known to be important (e.g. Hinch andartins, 2011; McKinnell et al., 2011), however, this model set was performed despite not havingSST for QCS because it represents the longest time period available with a selection of variablesfor both regions. The individual models run within the model set are specified in Table A4.3-13.Table A4.3-13. Model specifications for the 1969-2004 (brood years) model set. This table shows the variablesincluded in each of the 8 models tested (i.e., M1 to M8) within this model set. Table 4.4-1 explains whichspecific data sets were used for each of these variables. “Rank of model” reflects the AIC c score showinglevel of support (#1 ranked model had the highest level of support and lowest AIC c score).Region Variable M1 M2 M3 M4 M5 M6 M7 M8QCS Salinity X X X XQCS Discharge X X XQCS Wind X XSoG Temperature X X XSoG Salinity X X X XSoG Discharge X X XRank of model 3 4 5 2 7 8 6 1The results show that the models with the most support are M8, M4, M1, then M2, with strongsupport for models M8 (SoG SST) and M4 (QCS SSS and discharge) in particular (Table A4.3-14 and Table A4.3-15). However, the AICc scores indicate that there is little difference in degreeof support among these four models (∆AICc = 2.28). For SoG during this period, temperature(M8) is more valuable for explaining the observed variability in Fraser River sockeye salmonproductivity than salinity (M7). Overall, the analysis of this time period shows that there issupport for both QCS and SoG models – the top ranked model was for SoG, the second for QCS,and the third was the global model, including both regions. These results show that for theseparticular variables, over this particular time period, there is no clear evidence of any differencebetween the explanatory value of the two regions; however, the absence of temperature data forQCS is a substantial shortcoming of this model set, and chlorophyll is not included in any model.252