Candidate explanatory variables, their inter-correlations and relations to salmonids mortality resulting from collected data (N − rotation speed (rpm), U − peripheral speed (m/s), H − water head (m), Q − nominal discharge (m³/s), D − diameter (m), L − fish length (mm) and mortality (unitless, range = 0–1)). Distribution histograms of each variable (on the diagonal), bivariate scatterplots with a fitted line (below the diagonal) and Pearson coefficients of correlation (above the diagonal) with the following significance levels: *** < 0.001; ** < 0.01, * < 0.05, ° < 0.1.