The Amazon Basin is the largest and more pristine watershed in Brazil with the highest freshwater fish diversity in the world and sustaining widespread small-scale fisheries. Although large tracts of the Amazon remain in good ecological condition, excessive fishing pressure had decreased the size and abundance of some large commercial fishes. In the last decades, several locally based and bottom-up co-management systems emerged in the Brazilian Amazon, on which local communities manage fishing territories (usually floodplain lakes), by excluding outsiders that do not follow management rules, such as fishing restrictions or no-take areas. Co-management may improve fishing yields and increase fish abundance in the more productive white water floodplains. Our research group have studied use of natural resources and fisheries several Amazonian rivers, such as the black water Negro River, the clear water Tocantins River and Tapajós River, besides the white water Solimões and Lower Amazon rivers. The population living in Amazonian rivers belong to the cultural groups of ribeirinhos or caboclos and aboriginal indigenous. Caboclos are descendants of aboriginal indigenous people and Portuguese colonizers, plus people from African descent, but more recently there has been immigration of people from the Northeastern Brazil. They live along the floodplains of the large Amazonian rivers and they have a mixed economy based mainly on small-scale agriculture (cassava, to produce flour), fisheries and cattle ranching. Such economic activities are closely dependent on the water cycle, marked by a low and high water season. Fisheries done by caboclos are usually artisanal. In some areas the main fishing vessels are still paddled canoes, while in others low power motorized canoes predominate. There are exceptions: catfishes for example have received a strong and semi-industrial pressure in the main channel of the Amazon River and its estuary . Overall, fishing is done with multiple gears (handline, harpoons, and castnets), but the most widely used are gillnets. They are usually low income people with low political power, although some communities has organized themselves to get exclusive rights to some fishing grounds through co-management systems, such as the fishing accords or extractive or sustainable reserves. These riverine populations could be considered as being vulnerable, especially those from the Tapajos River, which has waters that are less productive and hence have lower fish biomass and lower availability of large sized commercial fish. Furthermore, these people rely mostly on fish as a source of animal protein, and are thus more vulnerable to environmental or anthropogenic changes that could affect fish ecology and fish abundance, such as long and unusual periods of drought (climatic changes), dams, mining and excessive fishing pressure. The occurrence and efficacy of local co-management initiatives to promote biodiversity conservation or sustainable use of natural resources are largely unknown for most of the Brazilian Amazon, especially in the less productive black and clear water rivers. We will focus our research in the Tapajós River. The Tapajós River has a clear water type, which is oligotrophic with low levels of sediment and nutrient concentration. There are two CUs of sustainable use in the lower section of Tapajós River: The National Forest of Tapajós (FLONA) and The Extractive Reserve of Tapajós-Arapiuns (RESEX). The FLONA was created in 1974 with the primary objective of sustainable use of timber, and only in 1992, it also included fauna protection. On the other hand, the RESEX was officially created in 1998, after a popular struggle against illegal logging. In relation to fisheries, both CUs only allow artisanal fishing gear, such as longlines, gillnets, hand lines and harpoons.