Small-scale fisheries and aquaculture (SSFA) sustain nearly half a billion people worldwide but face major challenges, including post-harvest food loss. This guidebook provides a practical, adaptable resource to help practitioners understand and reduce loss across diverse contexts. Designed for researchers, agencies, civil society, and value-chain actors, it combines tools for data collection, systems change, and community engagement. A central focus is building strong relationships and mobilising local agencies to create effective, lasting solutions.