Sensitivity of the F35% Target Fishing Rate to Variation in the Maturity Schedule

Monte Carlo simulation experiments were conducted to explore how variability in the maturity schedule for English sole Pleuronectes vetulus is transformed into variability in estimates of F35%. Random values were generated for age at 50% maturity and the maturity slope coefficient for each of 10935 combinations of 8 factors. From these simulated data F35% values were derived and summarized for each experimental treatment as an average F35% value and coefficient of variation. The summary statistics were then transformed and analyzed using forward stepwise linear regression to determine the relative importance of different factors plus a quadratic term were required to account for 90% of the variability in the data, whereas in the model for coefficient of variation in F35% all eight factors, plus interaction term and a quadratic term, were required to account for 90% of the variability in the data. In both models the age at 50% maturity and the age at 50% selection were the two most important explanatory variables.