Trace metal pollution in tropical freshwater ecosystems poses growing public health concerns, particularly in regions where fisheries are central to food security; however, little is known about metal exposure risks in the Western Amazon. This study presents the first assessment of trace metal concentrations in fish sold at the main market in El Coca, a rapidly growing city in the Ecuadorian Amazon. We analyzed 11 trace metals in 17 commercially important species and estimated seven health risk indices based on two fish consumption scenarios and international reference dose standards. Our results show that all species exceeded recommended thresholds for arsenic, mercury, and lead, while one species surpassed guidelines for aluminum. Metal concentrations varied by species and river of origin: small catfish from the Payamino River had elevated cadmium, chromium, copper, and manganese levels, potentially linked to upstream gold mining, whereas larger catfish showed higher mercury and arsenic accumulation. Monte Carlo simulations of risk indices suggested overall some disease risk, but the lack of local demographic data limits accurate assessments for vulnerable groups. Despite sampling limitations, our findings offer the first baseline for monitoring trace metal exposure in the northern Ecuadorian Amazon and underscore the need for targeted public health strategies in this understudied region.

Fisheries in the Ecuadorian Amazon support subsistence, cultural identity, and local economies, yet facethreats from oil extraction, agricultural expansion, and overfishing. This study integrates Local Ecological Knowledge (LEK) and fishing practices from 53 Kichwa, Siona, and Cofán fishers in seven communities across the Napo and Aguarico watersheds. Using structured and open-ended questionnaires, we recorded information on fishing techniques, seasonal patterns, perceived environmental changes, and threats to fisheries. Fishers reported 30-40% decline in abundance, that over 25% of fishers relate to oil extraction. Results show differences in fishing practices among Indigenous groups and communities, and identify key ecological insights including fish migration routes, spawning habitats, and seasonal abundance patterns. Despite high species richness, approximately 15 species dominate catches. Differences in market access and seasonal isolation also risk the food security of the more distant communities. Our results show that LEK in this data-poor region is not only a source of ecological information, but also a foundation for differentiated governance capacities, with some communities already translating knowledge into collective rules. These findings offer a baseline for culturally grounded, participatory co-management and community-based monitoring of Amazonian freshwater fisheries in Ecuador.

The Western Amazon is a highly biodiverse area. Zooplankton diversity studies in the region have been primarily conducted in Peru and Colombia, with limited research in the Ecuadorian Amazon. To address this gap, our research aimed to enhance taxonomic knowledge and understand zooplankton diversity patterns in the Napo and Pastaza lower basins at different spatial and temporal scales. Two sampling expeditions were conducted in the high waters of 2021 and rising waters of 2022. Dry conditions in 2021 led to lower-than-expected water levels. The study identified 107 zooplankton species, revealing variations in richness and composition between years, lakes, and depth strata. Grande Lake, deeper and wider than Delfincocha, exhibited significant turnover variations across strata in both seasons. Despite a relative longitudinal homogenization between channels and floodplains during high waters, beta diversity across vertical and temporal gradients highlighted complex dynamic zooplankton communities in both lakes. In addition, we include the first records of 44 taxa for the Ecuadorian Amazon and 36 for Ecuador. These findings emphasize the need for targeted research and conservation efforts in the face of escalating environmental threats to the Western Amazon.

Small-scale inland fisheries in the Amazon are critical for food security, yet their sustainability is increasingly threatened by overexploitation and environmental degradation. In data-limited contexts such as the northern Ecuadorian Amazon, the absence of continuous monitoring constrains the development of adaptive management strategies. This study develops an integrated socio-ecological baseline to support the establishment of fisheries agreements in five Indigenous communities of the Napo and Aguarico rivers. Through a participatory monitoring approach, we generated reproductive parameters (gonadosomatic index, fecundity, size at first maturity), population structure metrics, and length–weight relationships for key subsistence species across three hydrological phases. Reproductive investment exhibited marked seasonality, with peak gonadosomatic indices during rising waters in most species, identifying a critical period for protection. Life-history strategies ranged from high-fecundity periodic strategists to low-fecundity equilibrium species, implying differentiated vulnerability to harvesting. Community perceptions prioritized large migratory catfish and floodplain habitats, aligning with biological indicators of vulnerability. High performance in technical training demonstrated the feasibility of long-term local monitoring systems. By linking biological indicators with local ecological knowledge, this study proposes a pathway from baseline assessment to adaptive co-management. The framework presented here provides a transferable model for strengthening sustainability, governance, and food security in tropical small-scale fisheries facing persistent data limitations.

Trace element contamination in Amazonian freshwater ecosystems threatens riverine food security. This study evaluated two post-harvest treatments—ethylenediaminetetraacetic acid (EDTA) and Lactobacillus fermentum—to assess cadmium (Cd) and lead (Pb) variations in edible muscle of four Amazonian fish species (Cichla monoculus, Pimelodus jivaro, Platynematichthys notatus, and Serrasalmus rhombeus). Concentrations were determined using ICP-OES. Platynematichthys notatus exhibited the highest baseline bioaccumulation, whereas C. monoculus showed the lowest. Although main treatment effects should be considered exploratory, distinct species-dependent trends emerged. EDTA achieved the highest Cd reduction in P. notatus (49.78%), while L. fermentum demonstrated notable Cd and Pb reductions in C. monoculus, P. notatus, and S. rhombeus. Conversely, relative concentration increases occurred in P. jivaro under both treatments, reflecting matrix-related effects. These findings suggest that post-harvest efficiency depends on fish species and metal type. Probiotic post-harvest processing represents a promising strategy for reducing dietary exposure to Cd and Pb in Amazonian fisheries, though optimizing operational parameters for community-level applications remains necessary.