Despite immense concern over amplified warming in the Arctic, physiological research to address related conservation issues for valuable cold-adapted fish, such as the Arctic char (Salvelinus alpinus), is lacking. This crucial knowledge gap is largely attributable to the practical and logistical challenges of conducting sensitive physiological investigations in remote field settings. Here, we used an innovative, mobile aquatic-research laboratory to assess the effects of temperature on aerobic metabolism and maximum heart rate (f Hmax) of upriver migrating Arctic char in the Kitikmeot region of Nunavut in the central Canadian Arctic. Absolute aerobic scope was unchanged at temperatures from 4 to 16°C, while f Hmax increased with temperature (Q 10 = 2.1), as expected. However, f Hmax fell precipitously below 4°C and it began to plateau above ~ 16°C, reaching a maximum at ~ 19°C before declining and becoming arrhythmic at ~ 21°C. Furthermore, recovery from exhaustive exercise appeared to be critically impaired above 16°C. The broad thermal range (~4-16°C) for increasing f Hmax and maintaining absolute aerobic scope matches river temperatures commonly encountered by migrating Arctic char in this region. Nevertheless, river temperatures can exceed 20°C during warm events and our results confirm that such temperatures would limit exercise performance and thus impair migration in this species. Thus, unless Arctic char can rapidly acclimatize or alter its migration timing or location, which are both open questions, these impairments would likely impact population persistence and reduce lifetime fitness. As such, future conservation efforts should work towards quantifying and accounting for the impacts of warming, variable river temperatures on migration and reproductive success.

中文翻译：

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在异常北极红点鲑（Salvelinus alpinus）中心肺功能的热极限：使用远程移动实验室进行的基于田野的调查。

尽管人们对北极地区的变暖现象有极大的关注，但仍缺乏生理研究来解决诸如北极红点鲑（Salvelinus alpinus）等珍贵的冷适应鱼类的相关保护问题。这一关键的知识差距很大程度上归因于在偏远地区进行敏感的生理学调查的实际和后勤挑战。在这里，我们使用了一个创新的移动水产研究实验室来评估温度对加拿大中部北极努纳武特地区Kitikmeot地区上游居民迁移的有氧代谢和最大心率（f Hmax）的影响。如预期的那样，在4至16°C的温度下，绝对有氧运动范围不变，而f Hmax随温度增加（Q 10 = 2.1）。但是，f Hmax急剧下降到4°C以下，并开始稳定在约16°C以上，在〜19°C时达到最大值，然后在〜21°C时出现心律不齐。此外，在16°C以上时，力竭运动恢复似乎受到严重损害。增加f Hmax并保持绝对有氧范围的宽广的温度范围（〜4-16°C）与该地区迁移北极红点鲑通常遇到的河流温度相匹配。然而，在温暖的天气中，河流温度可能会超过20°C，我们的结果证实，这样的温度会限制运动能力，从而损害该物种的迁徙。因此，除非北极红点鲑能够迅速适应或改变其迁徙时机或位置（这都是悬而未决的问题），否则这些损害很可能会影响种群的持久性并降低寿命。因此，