中文摘要：

高坝泄洪过程中,高速水流造成下游水体的总溶解气体（Total Dissolved Gas,TDG）过饱和极易使得水体中的鱼类患上气泡病,进而对下游水体的鱼类生存造成威胁。为了探究长薄鳅（Leptobotia elongate）幼鱼对TDG过饱和水体的探知回避能力,本实验以2月龄的长薄鳅为研究对象,记录其在不同TDG饱和度水体中的反应和趋向。结果表明,在120%TDG过饱和水体中,长薄鳅回避率为-20%,其对该饱和度下的水体表现出了一定的趋向性;TDG饱和度为130%时,长薄鳅回避率为-2%,无明显回避能力;TDG饱和度为140%时,长薄鳅展现出微弱的回避特征,其在清水与过饱和水体之间往复游动,最终回避率为12%;150%TDG过饱和水体中,长薄鳅体现出敏锐的探知能力,1-2 min后开始频繁游动,同时具有一定的回避能力,回避率为34%。长薄鳅的回避率与过饱和水体浓度呈现较强的线性相关关系,水体TDG饱和度越高,实验鱼回避现象越明显。

英文摘要：

High-velocity flow in the process of high dam flood discharge leads to total dissolved gas supersaturation（ TDGS） downstream of the dam,which can cause gas bubble disease in fish and can lead to acute mortality. Leptobotia elongate is an important economic fish species endemic to China,primarily inhabiting the upper Yangtze River and its tributaries. TDGS resulting from hydropower development on the upper Yangtze River threatens Leptobotia elongate populations. Leptobotia elongate spawns from April to June and juveniles,two to three months old,are especially vulnerable to TDGS. In this study,two-month-old Leptobotia elongate were used to explore avoidance characteristics to different degrees of supersaturation. Test fish,with an average weight of 1. 0 g and average length of 2. 5 cm,were acclimated for 15 d at 11-13℃ and dissolved oxygen of 5-7 mg/L,and fasted one day before testing. Four TDGS levels（ 120%,130%,140% and 150%） were set,with each treatment run in triplicate and 19-21 fish individuals per trial. Tests were conducted in low light and the position of the fish was recorded every 10 min to evaluate the perception and avoidance ability of Leptobotia elongate to TDGS water. Leptobotia elongate displayed a certain tropism at a TDGS of 120% and the rate of avoidance was-20%. Test fish did not display obvious avoidance at 130% supersaturation and the avoidance rate was-2%. Test fish showed weak avoidance and continually moved between saturated and supersaturated water at a TDGS of 140% and the avoidance rate was 12%. When the degree of TDGS was 150%,Leptobotia elongate were sensitive to supersaturated water and,after 1-2 m exposure,avoidance behavior was obvious,with an avoidance rate of 34%. There was a significant positive correlation between the avoidance rate of Leptobotia elongate and TDGS degree. These results provide a reference and basic data for the operation of hydropower stations and the establishment of water-related environmental standards in China.