Food insecurity, hunger and malnutrition have been on the rise in recent years, due to disruptions such as the COVID-19 pandemic, increasing climate shocks and conflicts. Decades of steady progress to reduce food insecurity and malnutrition were often attributed to increased food production and intensification of few food staple crops and livestock, however more recent focus has shifted to the role of small-scale producers and the importance of diverse and nutritious foods. This technical paper brings focus to the often overlooked ‘small fish’ which play an integral role in the food security and nutrition of people living in poverty and the livelihoods of those who harvest, process, market, trade and distribute small fish. The technical paper explores the various dimensions of the aquatic food system, with focus on supply chains of small fish, addressing drivers, scales, interactions and multiple outcomes and trade-offs, such as that of small fish used for food versus feed. Throughout, the work applies a human-centred perspective, emphasizing how people are involved in various stages of a food system, and how interactions and networks between them play a role in food system dynamics and outcomes. It is also emphasized how people play multiple roles within a food system, and thus should not be narrowly defined as fishers, processors or consumers. The paper documents project implementation and lessons from the FAO subprogramme titled “Implementing the Small-Scale Fisheries Guidelines for gender equitable and climate resilient food systems and livelihoods”, and the SmallFishFood, Ikan-F3, Dried Fish Matters, and Fish4Food projects led by the University of Bergen, the University of Amsterdam and the University of Manitoba.