Based on in‐depth anthropological field research in rural Japan, this paper analyses the ongoing reform of Japanese fishery governance and its social and environmental justice implications, as globally proliferating discourses on the ‘blue economy’ and ‘blue growth’ are driving the enclosure of one of the last vestiges of natural resource commons in small‐scale fisheries. Coastal fisheries in Japan are often idealized as one of the last bastions of resource co‐management in an industrialized country, with local cooperatives collectively controlling territorial fishing rights. However, demographic change, declining profitability, and dwindling resource stocks are challenging their viability. Reform of the fishery law, designed to stimulate new growth and industrialization – particularly in aquaculture – includes the opening up of coastal fishery resources to corporate investors, the strengthening of top‐down regulation, and the introduction of individual fishing quotas (IQ). The desire to boost domestic seafood production also has to be seen within the context of the double anxiety of high dependency on international trade for foodstuff and of Japan's vanishing rurality. This emphasis on private capital and presupposed economic and scientific rationality builds on the same rationale of blue economy and blue growth discourses, which promise financial along with ecological returns on large‐scale investments in sustainable ocean economies. Growth‐oriented reform in Japan now imperils successful resource co‐management in coastal small‐scale fisheries. Its analysis therefore offers deeper insights into the transformative as well as dispossessive potential of the global paradigmatic shift towards an intensified industrial exploitation of the oceans. The question of social and environmental justice is central in the re‐allocation of access rights to ocean spaces and resources and the re‐arrangement of decision‐making processes in fishery governance, as local fishing communities face a very real threat of dispossession and disempowerment.