(a) Standardized CPUE index at each step in the stepwise selection of variables for the tested models (only main effects). Each panel shows the standardized CPUE index as each explanatory variable is added to the model. The index obtained in the previous step (if any) is shown by a dotted line and for steps before that by grey lines. (b) Annual influence values for each explanatory variable in the final GLM model. (c) Statistics for explanatory power and influence of explanatory variables in the final GLM model.