Assessing the impact of artisanal and recreational fishing and protection on a white seabream (Diplodus sargus sargus) population in the north-western Mediterranean Sea, using a simulation model. Part 2: Sensitivity analysis and management measures

In this paper, the ISIS-fish model was used to assess the impact of spatial and seasonal management measures on the dynamics of the white seabream population (Diplodus sargus sargus) in the French Catalan fishery (north-western Mediterranean). This work is the second part of a paper ( Hussein et al., 2011) which describes the parameterization of the model. Here we carry out a sensitivity analysis to identify the most significant model parameters. The simulation results show that the model is particularly sensitive to some parameters such as natural mortality, stage length, fecundity, number of inactive days per strategy and gear standardisation factors. Second, the impact of several management measures was evaluated (e.g. marine protected areas (MPAs) in the nursery and spawning zones, changes in gillnet mesh size and fishing effort reduction). Management scenarios were then assessed and compared using a simulation design. The results indicate that the permanent closures in the white seabream juvenile habitat for all gears, a change in gillnet mesh size and fishing effort reduction would result in an important increase in the population biomass and catch. The closures of the spawning zones appear inefficient in restoring D. sargus biomass.