Total dissolved gas supersaturation from dams and power stations is a chronic freshwater pollutant that is toxic to animals with aquatic respiration. Laboratory ecotoxicology experiments have revealed capacity for captive fishes to saturoregulate by moving deeper, but field ecotoxicology research is largely lacking. We instrumented 94 brown trout in the Rysstad basin of the Otra River, Norway, with depth sensor acoustic transmitters and monitored their movements for 10 months. We found that the depths used by the trout largely protected them from the effects of total dissolved gas supersaturation, which ranged from 96% to 133% total gas pressure during the study. The depth use of fish was affected by sun position, lunar phase and spatial position in the river (i.e., available depth), and there was an extremely weak effect of total dissolved gas supersaturation that was counterintuitive (i.e., positive slope, movement toward surface). Depth traces of the fish revealed that nine fish died during the study, mostly coinciding with the first wave of supersaturation, consistent with observations of untagged dead fish with signs of gas bubble trauma found on the river bottom during this period (May-June). Overall, tagged trout exposure to total dissolved gas supersaturation depended on their use of depth, but responses to waves of extreme supersaturation at supraphysiological levels were weak and biologically insignificant, with individual variation and spatial position in the river most important in the model. Exposure to total dissolved gas supersaturation was mediated by individual differences in habitat use, which may be linked to activity and other traits that determine overall vulnerability to exposure to total dissolved gas supersaturation.

中文翻译：

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褐鳟 (Salmo trutta) 对受管制河流中总溶解气体过饱和的行为响应

大坝和发电站的总溶解气体过饱和是一种慢性淡水污染物，对具有水生呼吸作用的动物有毒。实验室生态毒理学实验揭示了圈养鱼类通过向更深处移动来达到饱和调节的能力，但在很大程度上缺乏野外生态毒理学研究。我们在挪威奥特拉河的 Rysstad 流域对 94 条褐鳟鱼进行了检测，使用深度传感器声波发射器并监测它们的活动 10 个月。我们发现鳟鱼使用的深度在很大程度上保护了它们免受总溶解气体过饱和的影响，在研究期间，总气体压力的范围从 96% 到 133% 不等。鱼类的深度利用受太阳位置、月相和河流空间位置（即可用深度）的影响，总溶解气体过饱和的影响非常微弱，这是违反直觉的（即正斜率，向地表移动）。鱼的深度痕迹显示，研究期间有 9 条鱼死亡，大部分与第一波过饱和同时发生，这与在此期间（5 月至 6 月）在河底发现的带有气泡创伤迹象的未标记死鱼的观察结果一致。总体而言，标记的鳟鱼暴露于总溶解气体过饱和度取决于它们对深度的利用，但对超生理水平的极端过饱和度波的反应较弱且生物学意义不大，个体差异和河流中的空间位置在模型中最为重要。暴露于总溶解气体过饱和是由栖息地使用的个体差异介导的，