Fish assemblages and diversity in three tributaries of the Irrawaddy River in China: changes, threats and conservation perspectives

Incompletely known fish assemblages and species diversity are substantial obstacles in fish conservation, particularly when their aquatic habitats are under threat due to rapid human-induced changes. Fish assemblages and diversity in three tributaries of the upper Irrawaddy River in China (the Dulong, Daying and Ruili rivers) were examined based on field collections and literature resources. The newly compiled fish assemblage recorded 85 species (in 8 orders, 20 families and 51 genera) distributed in the upper Irrawaddy. The fish compositions in the Daying (67 species, 44 genera, 19 families, 7 orders) and Ruili rivers (65 species, 44 genera, 19 families, 8 orders) were more similar to each other and more speciose than that in the Dulong River (14 species, 10 genera, 4 families, 3 orders). Two indices of taxonomic diversity (the average taxonomic distinctness (Δ+), and the variation in taxonomic distinctness (Λ+)) were used to discriminate four collections spanning a ten-year period. A decrease in taxonomic diversity and an increase in unevenness of the fish assemblages were found in both the Daying River and Ruili rivers, which indicated that the impacts were accumulated gradually during this decade, when dams and the spread of non-native species were major threats. Comparatively speaking, the Dulong River is still in a near-natural state, and thus the fish community has experienced less disturbance. In situ conservation (nature reserves and tributary protection) and ex situ conservation (artificial propagation and release) should be combined and managed to promote fish conservation in the future. Les assemblages de poissons et leur diversité spécifique incomplètement connus sont d’importants obstacles à la conservation des poissons, en particulier lorsque leurs habitats aquatiques sont menacés en raison des rapides changements induits par l’homme. Les assemblages de poissons et leur diversité dans trois affluents de la rivière Irrawaddy supérieure en Chine (les rivières Dulong, Daying et Ruili) ont été étudiés sur la base de collectes sur le terrain et des ressources de la littérature. L’assemblage de poissons nouvellement compilé comporte 85 espèces (8 ordres, 20 familles et 51 genres) répartis dans l’Irrawaddy supérieure. Les compositions de poissons dans les rivières Daying (67 espèces, 44 genres, 19 familles, 7 ordres) et Ruili (65 espèces, 44 genres, 19 familles, 8 ordres) sont plus semblables les uns aux autres et plus riches en espèces que dans la