Abstract: Vertical mergers are mostly perceived in the literature as a way of reducing production and transaction costs. However, vertical restrictions or raising rivals ’ costs (RRC) are taken into great consideration by the antitrust authorities as potential consequences of vertical integration. The case of the French tuna industry seems of particular relevance to look at causes of vertical integration and the implications on competition within the industry. In 1994, a major fishing and transportation company has been taken over by a member of the French tropical tuna oligopoly. This company was previously supplying fish for all the canneries without earning extra profits. Since the institutional change, trade has been diverted and the co...