Modelling the use of two fishery access rights, concessions and licences, in the red sea urchin, Strongylocentrotus franciscanus (Agassiz), fishery at Santo Tomás, Baja California, Mexico

Various stages of the red sea urchin, Strongylocentrotus franciscanus (Agassiz), fishery were simulated to evaluate the effect of two types of access rights under Mexican law: concessions and licences. The resource biomass was evaluated using the critical depensation and Schaefer models. Each model was evaluated as a static or dynamic system. The parameters required for each model were determined from government data and by generating stochastic numbers using the Monte Carlo method to adjust to a dynamic model. In general, both models predicted catches smaller than those observed. The five-year-period simulation for both models showed a drop in biomass when licences are issued, whereas a similar simulation for concessions resulted in increased biomass, except when high temperatures occurred. Our results suggest that issuing concessions rather than licences is the best option to conserve the fishery.