Shared stocks, game theory and the zonal attachment principle

The outcomes of a Nash-Cournot game and a game of cooperation supported by a threat strategy are compared. The discussion is related to the ongoing conflict over the mackerel stock in the Northeast Atlantic. Despite the absence of a comprehensive management agreement, the outcome of the mackerel fishery is nowhere near what is predicted by the Nash-Cournot equilibrium. To the contrary, the countries involved seem to be engaged in an informal cooperation, supported by an implicit threat of mutually assured destruction should any single one compete too aggressively. The zonal attachment principle of dividing the total catch from shared stocks is also examined and found wanting in many cases.