Dams and Impounded Rivers - River Dynamics and Integrated River Management - page 452

Fig. 7.47 (a) Stage variation at Yichang and Jianli under natural conditions and the spawning time of the Chinese
carp; (b) Relation between the discharge increment and flux of fries (after Cao et al., 1987)
Figure 7.47(a) shows the stage variations at Yichang and Jianli and the time of fish spawning, in which
the solid circles represent spawning of fishes (Cao et al., 1987). Figure 7.47(b) shows the relation between
the discharge increment in a few to ten days and the flux of the fish fries, in which the flux of fries lags
about 4-6 days behind the discharge increase. The figures demonstrate that the spawning of the fishes is
excited by the stage and discharge increase. The higher the discharge increase, the higher the flux of fries
will be. The TGP Reservoir regulates the runoff and especially moderates the stage rise and discharge
increase in May, which affects the spawning of fishes and reduces the flux of fries. Now artificial spawning
and hatching has successfully solved the problem. The effects of the impoundment on fisheries have been
mitigated to a minimum.
7.4.3.6 Endangered Aquatic Species
There are several important species in the river, Chinese sturgeon, white-flag dolphin, Yangtze alligator,
giant salamander, and the black finless porpoise are several among them. The reservoir has little impact
on the living conditions of the Yangtze alligator, giant salamander, and black finless porpoise. Chinese
sturgeon usually swim upstream to spawn and then return to their home grounds. The Gezhouba Dam has
made it impossible for the fish to swim up and down the river during the spawning period. But the
sturgeon has spawned naturally in the waters below the dam. Artificially induced breeding of fry has also
been successful.
The white-flag dolphin usually lives in meandering and braided sections below the TGP Dam. Studies
indicate that the species finds its best habitats in meandering and braided-meandering sections because it
has been accustomed to the backwater zones created by the convex bank of meanders or the gravel and
sand bars in the braided channels (Chen and Hua, 1987). The regulation of the flow by the reservoir and