LAUSR

Fish biodiversity in transboundary river systems is critical for regional ecosystem health but remains under pressure from varying degrees of human impact. This study examines fish diversity patterns in the Tumen River Basin, distinguishing ecological differences between its main stem and tributaries. Using species and functional diversity indices, we analysed community structure and assessed environmental influences on biodiversity. Results indicate that the main stem, minimally disturbed by human activities, supports richer species composition and greater functional diversity, serving as an ecological refuge. In contrast, tributaries experience significant ecological pressure from agricultural runoff and urban activities, leading to reduced diversity and biotic homogenization. These findings underscore the importance of focused water quality management and habitat restoration to safeguard fish biodiversity. Our research provides a scientific foundation for conservation strategies tailored to the unique needs of border rivers, offering insights for transboundary ecological management.