Several superhigh dams (greater than 200 m in height) and many high dams have been built in the upper Yangtze River basin in recent years, and these dams have made total dissolved gas (TDG) supersaturation a serious environmental problem. A few studies have examined the tolerance and avoidance characteristics of rare and endemic fish in TDG‐supersaturated water in the upper Yangtze River over the past 10 years. These studies focused on specific species and specific sizes and did not identify a regular pattern that can be applied to all resident fish in the upper Yangtze River. However, elucidating this type of pattern is crucial for fishery management and dam operations in the upper Yangtze River. Data on the median lethal time (LT₅₀), horizontal avoidance percentage, and vertical water depth of three rare and endemic species in the upper Yangtze River from previous studies were used in the current work. An exponential relationship was found between LT₅₀ of fish and TDG supersaturation. The avoidance percentage of fish has a linear relationship with TDG supersaturation. Fish in the upper Yangtze River can use depth compensation to avoid the threat of TDG when the saturation is 130% or above but rarely avoid the threat of TDG when the saturation is less than 125%. We also described the tolerance and avoidance characteristics of fish in a TDG‐supersaturated river downstream from a super‐high dam. When the dam discharged a two‐year flood, the LT₅₀ values of fish downstream ranged from 9.1 to 27.5 hr regardless of depth compensation. The avoidance percentage of resident fish ranged from 8.4 to 44.8%. The resident fish swam to a water depth of 2.43–3.33 m to avoid the threat of TDG.

中文翻译：

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长江上游珍稀鱼类对水电站总溶解气过饱和的耐受性和回避机制

近年来，长江上游流域已建造了数座超高水坝（高度超过200 m）和许多高水坝，这些水坝使总溶解气体（TDG）过饱和成为一个严重的环境问题。过去10年中，一些研究检查了长江上游TDG过饱和水中稀有和特有鱼类的耐受性和回避特性。这些研究集中于特定的物种和特定的大小，并未确定可应用于长江上游所有常驻鱼类的规则模式。但是，阐明这种类型的模式对于长江上游的渔业管理和大坝运营至关重要。中位致死时间数据（LT ₅₀目前研究中使用了长江上游三种稀有和特有物种的水平避开率和垂直水深。在鱼类的LT ₅₀和TDG过饱和之间发现了指数关系。鱼的回避率与TDG过饱和度呈线性关系。当饱和度为130％或以上时，长江上游的鱼类可以利用深度补偿来避免TDG的威胁，而当饱和度小于125％时，很少可以避免TDG的威胁。我们还描述了超高水坝下游的TDG超饱和河中鱼类的耐受性和回避特性。当大坝泄洪两年时，LT ₅₀不管深度补偿如何，下游鱼类的最大价值在9.1至27.5小时之间。居民鱼类的回避率在8.4％至44.8％之间。居民鱼游到水深2.43–3.33 m以避免TDG的威胁。