The unique functioning of a pre-Columbian Amazonian floodplain fishery
Archaeology provides few examples of large-scale fisheries at the frontier between catching and farming of fish. We analysed the spatial organization of earthen embankments to infer the functioning of a landscape-level pre-Columbian Amazonian fishery that was based on capture of out-migrating fish after reproduction in seasonal floodplains. Long earthen weirs cross floodplains. We showed that weirs bear successive V-shaped features (termed 'Vs' for the sake of brevity) pointing downstream for outflowing water and that ponds are associated with Vs, the V often forming the pond's downstream wall. How Vs channelled fish into ponds cannot be explained simply by hydraulics, because Vs surprisingly lack fishways, where, in other weirs, traps capture fish borne by current flowing through these gaps. We suggest that when water was still high enough to flow over the weir, out-migrating bottom-hugging fish followed current downstream into Vs. Finding deeper, slower-moving water, they remained. Receding water further concentrated fish in ponds. The pond served as the trap, and this function shaped pond design. Weir-fishing and pond-fishing are both practiced in African floodplains today. In combining the two, this pre-Columbian system appears unique in the world. ; This research was funded by grants to D.M. from the Institut Universitaire de France, the Institut Ecologie et Environnement (INEE)/CNRS (Projets Exploratoires Pluridisciplinaires program), the Mission pour l'Interdisciplinarité of the CNRS, the TOSCA committee (Terre Solide, Océan, Surfaces Continentales, Atmosphère) of the CNES (French National Center for Space Research), the Groupement de Recherche Mosaïque (GDR 3353, INEE/CNRS); and by grants to R.B. from the Institut Ecologie et Environnement (INEE)/CNRS (Projets Exploratoires Pluridisciplinaires TOHMIS), to L.R. from the Swiss National Science Foundation (SNSF) [grant no. P2BEP2_172250] and to U.L. from the European Union's Horizon 2020 research and innovation programme [Marie Skłodowska-Curie actions, EU project 703045]. This work was supported by public funds received in the framework of GEOSUD, a project (ANR-10-EQPX-20) of the program Investissements d'Avenir managed by the French National Agency. Research was also funded in part by the European Research Council project 'Pre-Columbian Amazon-Scale Transformations' (ERC-CoG 616179) to J.I. Data for Supplementary Figs S2 and S9 were provided by TerraSAR-X/TanDEM-X (grant no. DEM_OTHER1040).