Who benefits from larger fish? Size-structure dependence and the distribution of conservation gains in a shared fishery

A minimum size limit costs fishers the small fish they can no longer land. The fish that survive are caught largerlater. In a fishery shared by several groups of users, the users who pay the cost are not always the users whoreceive the gain. We show that two characteristics of each user decide who loses and who gains. The first issize-structure dependence: the share of the user’s revenue that comes from fish large enough to remain legalunder the new limit. It decides whether the user loses or gains. The second is fishing power on large fish: theuser’s share of the catch of large fish. It decides how much of the extra catch the user receives. Neither is theuser’s economic dependence on the species. We apply the theory to French sea bass with an age-structuredmodel of twelve commercial fleets and recreational fishers.