The location of pre-Angkorian archaeological sites in the main course of the Mekong River Basin between Kratie (Cambodia) and Champassak (Laos) has been attributed to local populations’ attempts to control goods moving in and out of the hinterland based on Bronson’s model of river hierarchies in Southeast Asia. These interpretations have placed an emphasis on trade, in addition to rice cultivation, as a marker for social complexity and wealth accumulation. In this presentation I will argue that the location of these sites can be linked to fish resources, and that social complexity can be similarly attributed to societal responses to fisheries management, adding to an increasing list of examples of convergence in cultural niche construction surrounding floodplain fishery in tropical river environments. In doing so, the essay reviews two data sets that are rarely used to discuss the selected archaeological material: regional fish ecosystems and traditional ecological knowledge of fishing practices among local communities. The study examines fish migration patterns, and explores traditional fishing practices connected to the systematic exploitation of the two main ecological niches linked to the reproductive life of fish –flood plains and deep pools. The location of these fishing grounds and the constraints that fishing resources impose on people is discussed in relation to archaeological data and livelihood activities related to fishing and fish processing. The discussion will then explore similar examples of flood plain fisheries management in the Amazon and Congo River Basins.