Table 4.

Identification and description of environmental and socioeconomic threats in the three Amazonian river basins sampled during the fieldwork: Upper Xingu River, Lower Tocantins River, and Mid Negro

Threat	Description of threat	Upper Xingu River	Lower Tocantins River	Mid Negro River
Alteration and loss of fish habitats due to deforestation of riparian vegetation	Habitat conversion of riparian communities, from expansion of agriculture, cattle ranching and urbanization in floodplains	Intensively verified	Moderately verified	Not yet relevant
Effect of reduced river flow due to deforestation of headwater areas	Changes in upland areas (deforestation, expanding cattle ranching, urbanization) resulting indirectly in greater sediment loads and contaminants such as fertilizers and pesticide from run-off	Observed conversion of natural vegetation into huge areas of soybean crop fields	Moderately verified	Not yet relevant
Effect of environmental contaminants on the water quality	Direct contamination of rivers from increased dumping of organic and solid waste into rivers from expanding urban areas and from activities such as intensive agriculture and mining	Potential contamination of waters from agricultural fertilizers and pesticides	Urban sewage pollutants	Urban sewage pollutants
Effect of hydroelectric reservoirs on diversity and fish communities	Transformation of a lotic environment into a lake eradicating or reducing populations of rheophilic fish species, and providing favorable conditions for lentic species to proliferate	Moderate and specifically located effect from small hydroelectric plants	Tucuruí dam and plant operation: overall drastic effects on natural habitats and fish communities	Not relevant
Effect of infrastructure on diversity and fish communities	Changes in hydrological regimes through construction of infrastructure such as roads, ports and navigation channels	Moderate impact	Severe impact	Not relevant
Threats to turtles and freshwater mammals	Illegal hunting and commerce of wildlife	Moderate impact in the upper region but very severe in the lower portion (Belo Monte region)	Severe impact	Moderate impact
Effects of fishing conflicts	Detected growing number of conflicts among natural resource users	Moderate conflict between sport and subsistence fishing	Severe conflict among commercial fishing interests	Moderate conflict between ornamental and sport fishing
Decline of ornamental aquarium fishing	Capture of ornamental fish species for aquarium international commerce	Not relevant in the upper region but important in the lower area of Volta Grande do Xingu	Not relevant here	Negative socioeconomic effect due to decline in demand; fishermen are now starting to seek their livelihoods in other activities, such as agriculture
Effects of deficient implementation of fishing regulation	Lack of organizational and institutional capacity to deal with fishing in a participatory and integrated manner	Sport fishing observed here to be organized to take advantage of immediate income of fishing opportunity	Several fishing colonies exist but conflicts are still severe due to the lack of fishing regulation and implementation	Weakness of organization due to present decline in ornamental fishing
Effects of deficient dialogue between participant actors of fishing social organizations	Social organizations play a significant role in enabling fishery management to ensure sustainability	Strong organization among owners of sport fishing accommodation but low concern for sustainability	Conflicts among subsistence, commercial and sport fishing	Drastic decline in dialogue due to decline in demand for ornamental fishing
Effects of overfishing	Overexploitation of fishery resources is observed when fish stocks are suppressed to a level where fishing in a given region is no longer sustainable, that is, there is a need to increase fishing effort and stocks are not replenished naturally	Competition between sport fishing and artisanal subsistence fishing. Smaller fish sizes.	Observed strong pressure on fishing stocks to meet demand	Sport fishing in increasing demand and ornamental fishing in decline
Effects of global climate change on aquatic environments	The published literature indicates that it appears highly possible that the predicted climate change over the next decades may well cause additional damage to Amazon aquatic ecosystems	Regionally subject to drying change due to intense and extended deforestation	Regionally subject to change due to drastic environmental change—Tucuruí dam	Forest still well preserved