Abstract The world's oceans cover three quarters of the global surface and account for about 80% of products taken by humankind from the aquatic systems. The spatial dimensions critical to fishery activities and management have been under constant change for many years because of pressure from two major interdependent forces. The first, of a geopolitical and socio-economic nature, tends to extend national jurisdiction outwards as far as possible from the coast, at the same time fragmenting the ocean area and its jurisdictions into ever-smaller geographical units linked to increasingly localized and decentralized governing institutions. The second, newer force favors increasingly larger geographical management units corresponding as far as possible to a particular harvested ecosystem, i.e. the aggregate of target, associated and dependent species, their productive environment and the exploitation system. This article looks at these two trends and their implications, and examines their convergence in the development of a more modern and responsible form of governance of fisheries.