This Fish Catch Monitoring Protocol provides a practical and community-friendly guide for collecting, recording, and analyzing fish catch information within Community Fisheries (CFi), particularly in riverine systems in Stung Treng and Rattanakiri provinces. These two provinces lie in the upper Mekong and Sesan–Srepok river basins, where fisheries play a major role in community livelihoods and biodiversity conservation. The protocol supports CFi committees, community researchers, and project teams in generating reliable data to understand seasonal fish catch patterns, fishing effort, species composition, and the ecological importance of river habitats; including deep pools, flooded forests, migration routes, and local fishing grounds. This narrative version focuses entirely on field-based catch monitoring. The methods emphasize simple, low-cost, and repeatable steps that fit the capacity of local communities and align with existing CFi management systems.