Interannual variations of the fish assemblage in the transitional zone of the Three Gorges Reservoir: persistence and stability

Abstract

The construction of dams may lead to dramatic changes in fish assemblages due to the loss of lotic habitat caused by impoundment, which have been well documented. However, knowledge of the temporal variation of fish assemblages in the transitional zone, which is an ecotone between lotic and lentic environments of the reservoir, is still very rare. In the present study, fishes in the transitional zone of the Three Gorges Reservoir were sampled from 1997 to 2002 and from 2006 to 2009 to investigate interannual variations of fish assemblages. The results showed that 9 families, composed of 77 species, were found in the transitional zone with Cyprinidae as the dominant group. By cluster analysis (CLUSTER) and non-metric multidimensional scaling analysis (MDS), assemblages were separated into two groups at a Bray-Curtis similarity value of 77.26%, representing the pre-impoundment period and post-impoundment period. Following analysis of similarity percentages of species contributions (SIMPER), shifts in abundances of Coreius guichenoti, Rhinogobio cylindricus and Coreius heterodon, etc. contributed most to the difference between the two groups. Surprisingly, contrasting to the drastic changes in lacustrine region, the fish assemblage in the transitional zone appeared to be relatively stable, since the ten core species caught were consistently recorded every year, and no significant species replacement occurred during our study period. Besides, the moderate index of persistence indicated persistence of the fish assemblage as well, in spite of the shift of some species. Based on the results of ordination and time-lag analysis, the fish assemblage in the transitional zone showed no directional change. We conclude that fish assemblage in the transitional zone of the Three Gorges Reservoir was stable across the surveyed years. Based on our results, we propose that maintenance of dynamic transitional zones in reservoirs will be useful for the preservation of fishes, particularly for the endemic species inhabiting the upper Yangtze.

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

“…Now these lotic species have almost disappeared in the reservoir area of the TGR (Institute of Hydrobiology, unpublished data). The same phenomenon occurred in the transitional zone (Wu et al, 2007;Gao et al, 2010;Yang et al, 2012). The relative biomass of the two Coreius species was over 70% in the 1970s in Banan reach, which declined to 46.87% in 199746.87% in −200046.87% in and 35.7% in 200546.87% in −200646.87% in (Wu et al, 2007.…”

“…These endemic species have evolved life history strategies primarily in direct response to the natural flow regimes (Cao, 2000). Based on this and other studies, we can see that the habitat of riverine fish has been seriously shrunk due to the impoundments of the TGR (Wu et al, 2007;Gao et al, 2010;Yang et al, 2012). Many lotic species were forced to move upstream and congregated into the limited fluvial upstream stretch, which exposed them to intensive exploitation and frequent natural or human-induced catastrophic events.…”

“…The impounding mode of the TGR provides a good opportunity to explore how fish assemblages have responded to these successive disturbances. Previous investigations have revealed evident and immediate fish assemblage changes in the lacustrine area and the transitional zone of the TGR (Wu et al, 2007;Gao et al, 2010;Yang et al, 2012). However, variations in fish assemblage in the riverine zone of the TGR remains poorly documented.…”

“…Dams and their associated impoundment can pose a great threat to biodiversity by altering water flow regimes, fragmenting habitats, modifying channel morphology and bed structure, changing water temperature and water quality, destroying reproductive environments, and blocking migration routes (Larinier, 2000). Notable upstream and downstream changes in fish assemblages, including species composition and relative abundance, have been observed after impoundment of reservoirs in many rivers (Erman, 1973;Winston, 1991;Gido et al, 2002;Jeffrey et al, 2003;Quinn and Kwak, 2003;Quist et al, 2005;Han et al, 2008;Johnson et al, 2008;Gao et al, 2010;Yang et al, 2012). The Three Gorges Reservoir (TGR), located in the lower section of the upper Yangtze River, is the largest hydroelectric station in the world, with a capacity of 3.93 × 10 10 m 3 , water level 175 m above sea level (asl) and surface area of 1080 km 2 (Huang et al, 2006).…”

Impact of the Three Gorges Dam on reproduction of four major Chinese carps species in the middle reaches of the Changjiang River

“…The Three Gorges Reservoir was initially impounded in 2003, and maximal water level reached 175 m above sea level in 2010. Many studies have investigated the eff ects of the change in hydrological conditions caused by the TGD on fi sh populations and communities (Gao et al, 2010;Yang et al, 2012) and revealed that many potamdromous fi sh species, which require long river reaches for migration and fast currents to transport eggs and larvae, have been impacted (Tang, 2010).…”