Optimum control of a bioeconomic system. The yellowfin tuna (Thunnus albacares) fishery in the eastern Pacific ocean

Abstract

The present value objective function of the fishery is maximized with the use of optimum control theory and information from 40,000 fishing sets of the Mexican tuna fishing fleet dating from 1980 to 1990. These data were used to obtain standard fishing days (SFD) as a measure of effort of the international fleet in the eastern Pacific Ocean. The Schnute model (1977) was modified and population growth rate, environmental carrying capacity and catchability coefficient were estimated. Operative costs, severa1 prices for the tuna caught and discount rates were used to obtain optimum biomass level (state variable) and effort (control variable). A constant catchability coefficient and a variable one, as an inverse function of biomass level, were considered. In any case, the effort being applied recently is almost double with rcspect to the economic optimum calculated in this work.