Total dissolved gas (TDG) is suggested to be one possible explanation for the extensive mortality of endemic fish suffered from gas bubble disease (GBD). We investigated the effects of water depth on adult Schitzothorax prenanti susceptibility to GBD in TDG supersaturated water 11.5 km downstream of Dagangshan dam in a two-year (2016–2017) live cage study. The probability of survival significantly increased at greater depth. The mortality of fish at 1–2 m was reduced to 50% of that at 0–1 m and the mortality rate for fish at 2–3 m was reduced to 25% of that at 0–1 m. Fish that survived in-situ TDG exposure in 2016 were relocated to equilibrated water and observed for 274 d to investigate sublethal effects of GBD. The surviving fish showed a substantial reduction in growth compared to the control group. During the flood discharge period in 2017, fish were re-exposed to TDG supersaturated water after a period of recovery (274 d) in equilibrated water. The mortality rate of re-exposed fish decreased to 35% compared to newly introduced fish. Our results contribute to the protection of aquatic organisms and the improvement of eco-friendly hydroelectric dam operations in the Yangtze River.

中文翻译：

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大坝下游过饱和气体暴露和再暴露成虫的耐受性和生长

总溶解气体（TDG）被认为是地方性鱼类因气泡病（GBD）大量死亡的一种可能解释。我们调查了水深对成年裂腹裂腹鱼的影响在为期两年（2016-2017 年）的活笼研究中，大岗山大坝下游 11.5 公里处的 TDG 过饱和水中对 GBD 的敏感性。在更深的地方生存的可能性显着增加。1-2m鱼的死亡率降低到0-1m的50%，2-3m鱼的死亡率降低到0-1m的25%。在 2016 年原位 TDG 暴露中幸存下来的鱼被重新安置到平衡水中并观察 274 天，以研究 GBD 的亚致死效应。与对照组相比，存活的鱼的生长显着减少。在 2017 年的泄洪期间，鱼在平衡水中经过一段时间的恢复（274 d）后重新暴露于 TDG 过饱和水。与新引进的鱼类相比，再暴露鱼类的死亡率降低到 35%。