Community structure characterization and diversity analysis of Schizothoracinae in four important tributaries of the middle Yarlung Zangbo River, Tibet plateau, China: Facing crisis and conservation significance

The Qinghai-Tibet Plateau is renowned for its rich yet fragile biodiversity, attracting global conservation attention. The aquatic biodiversity in the Yarlung Zangbo River's core area faces significant pressures, yet our understanding of fish community structures in its tributaries remains limited. To address this gap, we surveyed fishery resources and analyzed six Schizothoracinae species ( Oxygymnocypris stewarti, Ptychobarbus dipogon, Schizothorax oconnori, Schizothorax macropogon, Schizothorax waltoni, and Schizopygopsis younghusbandi ) across four major tributaries of the middle Yarlung Zangbo River (Dogxung Zangbo, Niangchu River, Lhasa River, and Niyang River). Results indicated that S. younghusbandi was the dominant species across all tributaries, while other species' dominance varied spatially. Notably, O. stewarti showed the lowest catch per unit effort (CPUE) in three tributaries (Lhasa, Niyang, and Niangchu Rivers), whereas S. waltoni had the lowest CPUE in Dogxung Zangbo. Fish diversity and evenness were significantly higher in Dogxung Zangbo and Niangchu River compared to Niyang and Lhasa Rivers, with the latter two exhibiting lower community complexity and greater anthropogenic disturbance. Abundance-biomass comparison curves revealed all communities experienced substantial disturbance, with Dogxung Zangbo being least affected. Cluster analysis and NMDS grouped the tributaries into two distinct clusters: Niyang and Lhasa Rivers, and Niangchu River and Dogxung Zangbo, reflecting high within-group community similarity. Using a priority protection assessment, S. macropogon emerged as the top conservation priority in Dogxung Zangbo, while O. stewarti ranked highest among the other three tributaries. These findings elucidate current fish community statuses, disturbance levels, and conservation challenges, offering critical insights for developing targeted protection strategies.