This paper presents findings from an experimental srudy on the harvesting behaviour of a set of fishers on Colombia's Pacific coast under both the presence and absence ofTerritorial Use Rights for Fisheries (TURF). The experiments are common-pool resource (CPR)-games where participams undertake ha1vesting decisions under a baseline scenario and two subsequent treatments (communication and self-regulation). The data are analysed using differenr statistical models. We find that fishers under TURF tend to coordinate their efforts when no treatments are introduced into the expeliment. However, once n-eannems are introduced, we obse1ve that self­ regulation outperforms communication in reducing haivest levels. This situation can be viewed as a consequence of the interna! struggles between TURF fishers, highlighting the need for regulation. We conclude that a TURF designation on its own is not sufficient to shape the preferences of the users of a CPR and needs to be accom­ panied by regulation to encourage coordination among players.