Southeast Asian lowland rivers are among the longest and most productive rivers for wild-capture inland fisheries in the world. They have many elements in common: they mostly arise on the Tibetan Plateau and have steep and turbulent upper courses within deep mountain valleys and flat lower courses associated with large deltaic wetlands. Their lower basins are now densely inhabited. This chapter deals with the lower, potamonic parts of the Ganges-Brahmaputra, especially the extensive deltaic and flood systems of Bangladesh, the Ayeyarwady (Irrawaddy), the Salween, the Chao Phraya and the Mekong and Lancang. It covers (1) the nature and status of freshwater and estuarine fisheries including description of habitats, main species (diversity) and their uses, capture methods and types of fisheries, recent harvests and trends in abundance and biomass and species diversity (key species), stock status and rates of exploitation and estimated sustainable production (2) aquaculture; (3) threats to fisheries production (4) management activities.