Effects of Total Dissolved Gas Supersaturation on the Swimming Performance of Two Endemic Fish Species in the Upper Yangtze River

Total dissolved gas (TDG) supersaturation has been identified as one of the possible negative environmental effects of the construction of dams in the upper Yangtze River. Juvenile Chinese sucker and Prenant’s schizothoracin fish were selected to evaluate the impact of TDG supersaturation on the swimming performance of fish in the Upper Yangtze River. The critical swimming speeds (U(crit)) of Chinese sucker were 4.06, 2.83, 2.87, 2.68, and 2.29 BLs(−1) at the TDG supersaturation levels of 100, 117, 122, 125 and 130%, respectively. The U(crit) of Prenant’s schizothoracin were 7.38, 4.32, 3.98, and 3.74 BLs(−1) at the TDG supersaturation levels of 100, 117, 125 and 130%, respectively. The burst swimming speed (U(burst)) of the two species also significantly declined with increases in the TDG supersaturation level. The present results demonstrate that the swimming speeds of Prenant’s schizothoracin that were exposed to 130% TDG supersaturation for 2 h exhibited significant recovery after 2 days, whereas the swimming speeds of Chinese sucker did not. The swimming speeds of Chinese sucker after 2 days of recovery were significantly reduced compared with those of control fish, whereas the speeds of Prenant’s schizothoracin returned to normal levels.