Complexities associated with the management of common pool resources (CPR) threaten governance at some marine protected areas (MPA). In this paper, using economic experimental games (EEG), we investigate the effects of both external regulation and the complementarities between internal regulation and non-coercive authority intervention—what we call co-management—on fishermen’s extraction decisions. We perform EEG with fishermen inhabiting the influence zone of an MPA in the Colombian Caribbean. The results show that co- management exhibits the best results, both in terms of resource sustainability and reduction in extraction, highlighting the importance of strategies that recognize communities as key actors in the decision-making process for the sustainable use and conservation of CPR in protected areas.