Technology-driven reduction of fish post-harvest loss could enhance food security and economic resilience.

Globally, only 54% of harvested fish is consumed directly by people, with the remainder lost to spoilage, inefficient processing, limited by-product utilization, or diverted to non-food uses. This inefficiency limits the nutritional, economic, and environmental potential of aquatic foods. Here, we assess the impact of targeted post-harvest interventions-including cold chain improvements, better handling practices, and valorisation of by-products, using a quantitative modelling approach with a qualitative synthesis of case studies and literature. We show that increasing net fish consumption by humans to 74% through feasible technological adoption could deliver an additional 850 million portions of fish per day, without harvesting a single extra fish. These "hidden harvests" could meet global dietary protein and micronutrient needs while reducing price to the consumer by nearly 10%. Whilst these findings should be seen as upper limits rather than expected outcomes. They highlight post-harvest optimisation as a critically underutilised lever for advancing nutrition security, reducing pressure on aquatic ecosystems, and achieving sustainable, equitable growth in blue food systems. Reducing waste, not simply increasing catch, is the key.