Summaries This article looks at community fisheries management in the Peruvian varzea , the resource?rich floodplain of the Amazon river. This dynamic and heterogeneous world gives rise to a wide range of uncertainties and ambiguities that challenge the long?term viability of community management efforts. The authors focus on the unpredictable nature of the hydrologic regime, which not only governs the annual cycle of fisheries production and availability but also determines the timing and intensity of productive activities such as agriculture, extraction of forest products and hunting. To survive, both the community members and their fisheries management systems have to adapt to the dynamics of the aquatic world in which they live. Flexible institutions are key to the viability of management systems which must bend with the chaotic rhythms of both social life and the surrounding natural world.