Evaluation of the Use of Two Fishery Access Rights; Concessions and Permits, in a Red Sea Urchin (Strongylocentrotus franciscanus) Fishery in Santo Tomás, Baja California, México
By Evlin Ramírez-Félix Héctor and Guillermo Manzo-MonroyABSTRACT
The resource biomass was evaluated using two models: critical depensation (Alle effect) and Schaefer pure compensation, each of which was evaluated both as static and dynamic (finite differences) systems. The required parameters for each model were determined from governmental data and by generating stochastic numbers using the Monte Carlo method to adjust with a dynamic model. The population parameter values that best fit the data by minimization of squared differences were; r = 0.35, (growth population intrinsic rate), k = 4,500 t, (natural equilibrium population), B = 2,500 t, (population catch biomass), q = 7 x 10 (catchability coefficient), ko = 120 t, (critical population biomass).
The main risks for the fishery were described by three groups: fishermen, fishery scientists and fishery administrators. The risks are poaching, the change of fishing areas during the renewal processes of fishing permits, and temperature variability.
The biomass was estimated by Bayesian probability. In general, both models predicted smaller than observed catches. The critical depensation model predicted a smaller biomass than did the Schaefer model.
The five year period simulation for both models shows a biomass drop within the fishing permits. Similar simulation with concession resulted in an increase in biomass, except when high temperatures were present. Our results indicate that the best option to preserve the fishery is to issue concession rather than permits.
KEYWORDS: red sea urchin (Strongylocentrotus franciscanus), Allee effect, critical depensation, Schaefer, Bayes
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