A significant component of aquaculture technology requires fishmeal and fish oil to produce feeds for farmed species and forms the basis for current optimism about blue food or foods from marine ecosystems. Industry spokespeople state that blue food is the future of a sustainable global agri-food system. Yet, recent debates around blue transformation do not adequately engage the ethical and sustainable sourcing of fishmeal and fish oil. At the same time, the voracious demand for pelagic fish for the production of feed has raised concerns over a possible dependence on wild fisheries (or a so-called fishmeal trap), friction of consumption, and the implications for the proliferation of transnational governance initiatives, such as the Global Roundtable on Marine Ingredients, which seek to govern the industry through market-based solutions. However, we lack an understanding of how the capitalist logic of growth that underpins the industry challenges or reproduces unequal power relations. This paper addresses this gap by investigating the rapidly changing role of the fishmeal and fish oil industry in producing blue food. Drawing on the ‘global ecological political economy’ heuristic framework, which centers on the dialectical relationship between ecology and social change, and data from event ethnography during the United Nations Oceans Decade in Barcelona, and interviews with blue food actors, this paper advances a justice-focus approach to blue transformation centering on power relations inherent in blue food policies, including questions of who governs blue transformation and in what contexts, who sets the terms, who are excluded in decision-making, whose interests are served, and what implications blue food production and consumption have for global environmental change. It concludes with pragmatic recommendations for actors and decision-makers in food governance spaces (particularly in increasing equity in policy for vulnerable populations) while offering normative analysis of transformative change in the agri-food system.