This paper analyses evidence about fishermen collectively organized bargaining over ex-vessel prices with a monopsony-like buying sector. Government allocation of collective catch quotas to fishermen organizations triggered the voluntary formation of cooperative fishermen’s bargaining associations, while a highly concentrated processing sector started behaving as a countervailing monopsony. This drove ex-vessel price determination into a sort of region-specific bilateral monopoly price bargaining. We estimate an empirical model of regional ex-vessel price determination, taking advantage of between-region and time regulatory differences to identify the differential effects on ex-vessel prices. The hypothesis tested is that the allocation of catch rights to fishermen organizations improved fishermen’s bargaining position when selling their fresh-chilled (perishable) catch. Our results support the tested hypothesis at only one of the regions studied. This region is precisely where fishermen were able to achieve more stable and better organized fishermen associations to deal with the price bargaining issue.