Fraser River sockeye salmon: data synthesis and cumulative impacts

The results show strong support for M10 (all marine life stages), with weak support for M4(Inshore Migration) and M6 (Return to the Fraser). Despite the large number of parameters (41)M10 had the lowest AICc providing strong support for this model. The next two models hadsubstantially fewer parameters but their AICc scores were 5-7 units higher than that of M10indicating some information loss as a result of the reduced number of parameters. Overall theseresults indicate that the marine component of the life stage is more important in explaining theoverall productivity than the freshwater component. However, it must be noted that there werelimited stressor data available for the freshwater component and those data available may nothave been the most appropriate data. The true interpretation of this result is that the marine dataavailable do a better job of explaining the overall productivity of Fraser sockeye, than thefreshwater data available over this time period. Estimates of effect sizes are presented in TableA4.3-5 for all models. Interpretation of the actual estimates, their magnitude and sign is difficultparticularly for very complex models with many covariates. As described in the previous section(Interpretation of results) models with only a few stressors are easier to interpret. If interested indigging into the estimates in detail, one should also obtain the estimates of variability for each ofthese parameters. These are available, but not provided in this document in the interest of space.Table A4.3-4. A4c candidate models ordered by AICc from best (lowest) to worst (biggest). M.ID=modelidentification, M.AIC=the estimated AIC for the model, num.obs=the total number of observations (i.e.,complete rows in the data set), num.par=the total number of fixed effects + random effects, Correction= thedifference between the AICc (corrected for small sample size compared to number of parameters) and theAIC, M.AICC= the AICc for the model, min.AICC = the smallest AICc observed within the model set,delta= the difference between the min.AICC and each M.AICC, and AICC_wts= the Akaike weight (i.e.,support) for each model.M.ID M.AIC num.obs num.par Correction M.AICC min.AICC delta AICC_wtsM10 1127.51 463 41 8.18 1135.69 1135.69 0 88.43M4 1135.78 463 32 4.91 1140.69 1135.69 5.00 7.25M6 1139.55 463 26 3.22 1142.77 1135.69 7.08 2.56M1 1131.35 463 50 12.38 1143.73 1135.69 8.04 1.59M5 1146.65 463 21 2.10 1148.75 1135.69 13.06 0.13M8 1151.31 463 19 1.72 1153.02 1135.69 17.33 0.02M2 1151.31 463 19 1.72 1153.02 1135.69 17.33 0.02M7 1152.93 463 23 2.51 1155.44 1135.69 19.75 0.0045M3 1155.74 463 25 2.97 1158.71 1135.69 23.02 0.00089M9 1156.46 463 26 3.22 1159.68 1135.69 23.99 0.00055238