Importance and spatial patterns of invisible fisheries in Amazonian clear-water rivers as revealed by fisher knowledge and collaboration.

The Brazilian Amazon contains the world's most diverse fish assemblages. These assemblages can be affected by freshwater fisheries, which provide food and income for riverine people, and by accelerating environmental change. We collaborated with local fishers to provide a comprehensive assessment of the spatial patterns of fish use in 3 clear-water rivers in the Brazilian Amazon: the Tapajos, Trombetas, and Tocantins. We interviewed 638 fishers in 39 communities about fish use for domestic consumption or sale, daily catches per fisher, and catch per unit effort (CPUE). We then assessed the influence of river identity, protected areas (PAs), forest cover, and landscape complexity (independent variables) on catches and CPUE estimated from interviews (response variables) through linear models. We also analyzed data from participatory catch monitoring in 21 communities along the Tapajos River (5668 fish landings). Twenty-one fish species were the most harvested and cited by interview respondents, 16 of which were migratory fishes, accounting for 82% of catches in the Tapajos River. According to fishers, daily fish catches per fisher were higher outside PAs (effect size 0.33) than inside, whereas CPUE was higher inside PAs than outside (-0.27). Catches were negatively associated with forest cover (-0.20), whereas river landscape complexity was positively associated with fish catch (0.96) and CPUE (0.66). These results can support management strategies, from regional to large scales, by reinforcing the relevance of PAs in clear-water rivers and showing the influence of landscape on fish catches. Our collaboration with fishers provided robust baseline data that can be used to inform inclusive, precautionary, and adaptive policies for conservation of threatened rivers.