From 2010 and onwards, a crisis has occurred over the distribution of a yearly total allowable catch (TAC) for the mackerel fishery in the Northeast Atlantic Sea. The European Union (the EU), Norway (NO), Iceland (IC) and the Faroe Islands (the FI) are players in this "mackerel crisis". In the present study, we use game theory in an attempt to rationalize the actual behaviour of these players during the mackerel crisis. We identify the profit of each possible coalition structure (the coalitional values) by using a fisheries economic model, and quantify the coalitional values empirically by statistical estimation of the relevant functional relationships. Based on the statistical estimations, we define a benchmark scenario and conduct a number of sensitivity analyses. To try to rationalize the outcome during the mackerel crisis, we require that a relevant coalition must be internally stable in the sense that no structure has an incentive to split up. By using the notion of internal stability, we are partly able to rationalize the actual coalition formation during the mackerel crisis.