The consequences of different scenarios in the management of the gillnet and purse-seine fisheries targeting Pomatomus saltatrix and Cynoscion guatucupa in southern Brazil: a bio-economic approach

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Abstract The bluefish Pomatomus saltatrix and the striped weakfish Cynoscion guatucupa are two of the most important commercially exploited species in southern Brazil. These species overlap spatially and temporally in southern Brazil and are exploited by a multi-purpose fleet. We analyse the consequences of different management options in terms of the bio-economy of the gillnet and purse-seine fisheries by considering P. saltatrix and C. guatucupa as the main targets. Development of the bio-economic model was based upon multi-fleet, single species models for P. saltatrix and C. guatucupa. The results are compared at the medium-term forecast level from stochastic simulations, and the technical interactions between the fleets that exploit the bluefish and striped weakfish are also addressed. The purse-seine fishery has a strong impact on the gillnet fishery. A management plan, which allocates moderate levels of effort for all co-existing fleets and interacting species, seems efficient, but effort should be controlled for P. saltatrix (for both fleets) and, for the gillnet fleet, relatively more trips should be allocated for C. guatucupa. For P. saltatrix, the best management relies upon the scenarios harvesting the oldest individuals.