Long-term changes in fish assemblage following the impoundments of the Three Gorges Reservoir in Hejiang, a protected reach of the upper Yangtze River

Abstract

Keywords: fish assemblage, long-term changes, the Three Gorges Reservoir, the upper Yangtze River The construction of the Three Gorges Reservoir (TGR) has seriously affected the fish assemblage in the impounded reaches. However, fish assemblage changes in the riverine zone remain poorly documented. In order to explore how upstream fish assemblage has responded to the successive impoundments of the TGR, fish investigations were conducted biannually in Hejiang, a protected reach of the upper Yangtze River, during the period from 1997 to 2011. Multivariate analysis revealed significant temporal differences in fish assemblage following the impoundments of the TGR. Prior to the impoundments, the fish assemblage appeared to be very diversified and very even. Immediately after the first and the second impoundment, the lotic species, such as Coreius guichenoti, Rhinogo-bio ventralis, Rhinogobio cylindricus and Coreius heterodon, became evidently dominant, due to their upstream migrations from the reservoir. However , two years after the third impoundment, the lotic species decreased dramatically, while lentic Hypophthalmichthys molitrix and Pelteobagrus vachelli became the new dominant species. Based on this and other studies , we can see the habitats of the riverine fish in the upper Yangtze River have been shrunk seriously because of the impoundments of the TGR. The cascade hydropower development in the lower Jinsha River will pose an accumulative effect on the aquatic environment in the mainstream of the upper Yangtze River. Free-flowing tributaries, such as the Chishui River, will play more important roles in fish conservation. RÉSUMÉ Changements à long terme dans les assemblages de poissons en Hejiang, un bief pro-tégé de la haute rivière Yangtsé, après mise en service du Barrage des Trois Gorges Mots-clés : assemblage de poissons, La construction du réservoir des Trois Gorges (TGR) a sérieusement affecté l'as-semblage de poissons dans les biefs aménagés. Cependant, les changements d'assemblage de poissons dans la zone lentique amont restent mal documentés. Afin d'explorer la façon dont les assemblages de poissons en amont ont répondu aux remplissages successifs du TGR, des investigations piscicoles ont été menées deux fois par an dans Hejiang, un secteur protégé de la rivière Yangtsé amont, au (1) Institute of Hydrobiology, Chinese Academy of Sciences, 7th southern road of East Lake,