COS 72-3 - ‘The way of the fish’: fishers’ knowledge as a source of ecological data on fish migration in tropical rivers

Background/Question/Methods

Migratory behavior is an important ecological feature of tropical freshwater fish, especially in the Brazilian Amazon, where seasonal flood pulse influence fish and fisheries. However, migratory data, which is costly and hard to obtain, is mostly lacking for most Amazonian fish. Notwithstanding its relevance, most of the available information on fish migration in the Brazilian Amazon came from required monitoring programs in dammed rivers, where such migrations may had been altered or even disrupted. Fishers have local ecological knowledge (LEK), which can fill knowledge gaps on fish migration in less studied and still pristine Amazonian rivers. We aim to analyze fishers’ LEK on migratory pathways of six fish species (or species’ groups) in the Negro and Tapajos rivers, in the Brazilian Amazon. These fishes perform ecological services (seed dispersal, nutrient cycling) and are among the most fished in both rivers. We interviewed 119 fishers (52 in Negro and 67 in Tapajos) in 16 fishing communities (eight in each river) along 243 km and 151 km of Negro and Tapajos rivers, respectively. We asked fishers to mark the migration routes of each fish species on maps (satellite image mosaic with community at the center of a 10 km radius line).

Results/Conclusions

We produced 38 maps based on accumulated fishers’ LEK for all studied communities and fish species. Fishers’ LEK indicated at least three fish species making long distance migrations in both rivers, the jaraqui (Semaprochilodus spp.) and the catfishes filhote (Brachyplatystoma filamentosum) and dourada (B. rousseauxi). However, the former migrates closer to the shore and across the floodplains, whereas the two larger catfishes move across the middle of the river channel. The migratory routes of other three fish species also include floodplains, some of which are located within protected areas. Comparison with previous results of studies on fishers’ LEK on fish migration in the Tapajos River and participatory monitoring of fisheries in both rivers reinforce the ecological importance of these rivers to the life cycle of the studied species and the small-scale fisheries they support. However, future development projects, such as planned dams, can disrupt these important fish migrations in the Tapajos River. Our results indicate that a change has to come to recognize the value of fishers’ knowledge to inform decision making and impact assessment, so to rethink an energetic development that threatens the integrity and connectivity of Amazonian rivers.
Funding support: National Academy of Sciences (NAS) and USAID (AID-OAA-A-11).