Climate change is predicted to impact freshwater aquatic environments through changes to water temperature (T water), river flow and eutrophication. Riverine habitats contain many economically and ecologically important fishes. One such group is the migratory salmonids, which are sensitive to warm T water and low O2 (hypoxia). While several studies have investigated the independent effects of T water and hypoxia on fish physiology, the combined effects of these stressors is less well known. Furthermore, no study has investigated the effects of T water and O2 saturation levels within the range currently experienced by a salmonid species. Thus, the aim of this study was to investigate the simultaneous effects of T water and O2 saturation level on the energetics and kinematics of steady-state swimming in brown trout, Salmo trutta. No effect of O2 saturation level (70 and 100% air saturation) on tail-beat kinematics was detected. Conversely, T water (10, 14, 18 and 22°C) did affect tail-beat kinematics, but a trade-off between frequency (f tail) and amplitude (A, maximum tail excursion) maintained the Strouhal number (St = f tail• A/U, where U is swimming speed) within the theoretically most mechanically efficient range. Swimming oxygen consumption rate ([Formula: see text]) and cost of transport increased with both U and T water. The only effect of O2 saturation level was observed at the highest T water (22°C) and fastest swimming speed (two speeds were used-0.6 and 0.8 m s-1). As the extremes of this study are consistent with current summer conditions in parts of UK waterways, our findings may indicate that S. trutta will be negatively impacted by the increased T water and reduced O2 levels likely presented by anthropogenic climate change.

中文翻译：

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极端温度加上缺氧会影响褐鳟（Salmo trutta）的游泳表现。

预计气候变化将通过水温（T水），河流流量和富营养化的变化影响淡水水生环境。河流生境包含许多经济和生态上重要的鱼类。其中一种是迁徙鲑鱼，它们对温水和低氧（缺氧）敏感。尽管有几项研究调查了T水和缺氧对鱼类生理的独立影响，但这些应激源的综合影响尚不为人所知。此外，尚无研究调查鲑鱼物种目前经历的范围内的T水和O2饱和度水平的影响。因此，本研究的目的是研究T水和O2饱和度水平对褐鳟鳟鱼稳态游泳的能量学和运动学的同时影响。没有检测到氧气饱和度水平（70和100％的空气饱和度）对拍打运动的影响。相反，T水（10、14、18和22°C）确实影响了尾拍的运动学，但是在频率（f尾音）和振幅（A，最大尾部偏移）之间进行了权衡，保持了Strouhal数（St = f尾巴•A / U，其中U是游泳速度）在理论上机械上最有效的范围内。游泳用水的氧气消耗率（[公式：参见文字]）和运输成本随着U和T水的增加而增加。在最高的T水（22°C）和最快的游泳速度（使用两种速度-0.6和0.8 m s-1）下观察到O2饱和度水平的唯一影响。由于这项研究的极端情况与英国航道部分地区当前的夏季条件一致，因此我们的发现可能表明S.