Fishery Managment: The Case of Tuna in the Eastern Tropical Atlantic

A simple bieconomic model (the Gordon-SChaefer model) is estimated for three species of tuna in the Eastern Tropical Atlantic. The model conformed well to the data and afforded estimates of maximum sustainable yield, bioeconomic and open access equilibria. Strong marginal stock effects were identified in all three fisheries, resulting in bioeconomic optima with stocks in excess of XMSY. While all three fisheries appear to have been economically over fished (fishery rents being driven toward zero), Yellowfin and Skipjack stocks do not appear to be biologically over fished (stocks appear to be at or slightly above X=K/2). For Bigeye Tuna there was strong indication of both economic and biological overfishing. A management policy employing transferable quotas and landings taxes is examined. Such a policy has three advantages: (a) optima yield will be harvested at least cost; (b) potential fishery rents may be distributed in a flexible fashion between West African and foreign flag vessels; and (c) a portion of the potential fishery rents may be captured by the management agency to defray the costs of administration, enforcement and research.