River ecosystems are ecologically, socio-economically, and culturally important, yet assessing their ecological condition remains challenging where long-term monitoring data are limited. Integrating ecological indicators with local knowledge of resource-dependent communities offers a practical and complementary approach to addressing information gaps in freshwater systems. This study assessed the perceived longitudinal ecological condition of the Labo River using the River Ecological Assessment Tool (REAT), while Fishers' Expert Rating (FER) served as a participatory method for quantifying fishers’ perceptions. Forty experienced riverine fishers rated the four Nature Function Indicators: Water Quality Index (WQI), Water Temperature Variability Index (WTVI), Aquatic Fauna Living Space Index (AFauSI), and Aquatic Flora Living Space Index (AFloSI). Results revealed an atypical longitudinal pattern of perceived ecological condition. The upstream section recorded the least favorable condition for WQI (6.81±2.41), AFauSI (7.10±1.29), and AFloSI (8.28±2.38), while the downstream section showed the most favorable perceived ecological condition, particularly for WQI (3.14±1.06). Significant longitudinal differences were observed for WQI, AFauSI and AFloSI, whereas perceived WTVI did not differ significantly among river sections. Despite these longitudinal differences, the assessment classified the overall perceived ecological condition of the Labo River as acceptable, although the upstream section was classified as having poor perceived ecological condition based on its composite FER score. This overall classification reflects fishers’ perceptions rather than direct measurements of the river's ecological integrity. Fishers also reported perceived declines in catches relative to five years ago, with most anticipating further declines over the next five years (upstream: 100%; midstream: 92%; downstream: 94%). Conservation and rehabilitation (38%) emerged as the leading management priority. Fishers’ local ecological knowledge may help identify changes in river conditions that warrant further investigation. Integrating FER with biophysical monitoring, fisheries assessment, and habitat evaluation is recommended to strengthen evidence-based and adaptive management of the river.
