Bioeconomics of technological interdependencies in a sequential shrimp fishery: optimal size of the industrial fleet in southern Gulf of California

Abstract

The bioeconomic sequential externalities in the white shrimp (Litopenaeus vannamei) fishery during 2014-2015 season in southern Sinaloa, Mexico, were analyzed by calculating the optimal size of the industrial fleet (trawlers) given the current oversized small-scale fleet (SSF: cayucos). For this purpose, we constructed a dynamic multi-fleet age-structured bioeconomic model with natural mortality-at-age and catchability-at-age. The distributed delay model was applied to simulate recruitment seasonality. The reproductive effect of seasonal sea surface temperature (SST) was also considered. The constant size of SSF was represented in status quo while reducing industrial fleet by -25%, -50% and -70%Maximizing net present value “NPV” of industrial fleet. The model showed the technological interdependencies of two fleets competing for one species and their respective externalities. The status quo fishery showed a deteriorated biomass (0.27, below MSY); overcapitalized fleet (especially for the SSF); fleets low NPV of resource rent, especially for the cayucos ($761 USD per season). The access limitation of trawlers presented a progressive improvement in all bioeconomic variables, mainly on biomass (+27%) and NPV resource rent for trawlers (+700%). The SSF presented positive marginal externalities (4%). However, biomass was still below MSY (0.34) and the fishery trade-off showed a 70% industrial fleet loss to overcome the negative externalities of the actual SSF status. Given the current conditions of the sequential shrimp fishery (i.e., overcapitalized, overexploited, difficulty to control SSF) the limitation of industrial effort to the area could be a viable strategy to improve the fishery bioeconomic performance. However, it is necessary to explore more management strategies that include the small-scale fishery to attained sustainable levels and higher profitability for users.