Through their multiple functions, refuges may be important for stream‐living fishes, particularly during stressful events such as seasonal low flow or drought. Coastal Cutthroat Trout Oncorhynchus clarkii clarkii is an ideal study organism to understand the importance of refuge. During seasonal low flow, lower water levels limit access to refuge and emigration, survival of fish is low, and predation risk is high. Under these conditions, we studied patterns of cover use from field observations and tested predictions from multiple hypotheses about cover use in a semi‐natural experiment. Boulders were the main cover selected by trout in natural streams. Trout disproportionately used cover near deeper water, and they selected larger‐sized cover in shallower water. Trout showed plasticity to switch among behaviours, concealing under cover and emigrating as first options, followed by grouping, and then habitat shifting. Lack of feeding and growth suggested that perceived threat of predation was a more important driver of behaviour than foraging. Emigration was also linked to cover, with higher levels of emigration associated with less cover availability, revealing a potential link between refuge and demography through emigration. Except for feeding, the intensity of alternative behaviours can increase or decrease depending on refuge availability. Collectively, findings of this work indicate that cover can be considered a critical limiting resource along with other fundamental resources of food and space for stream‐living fish.

中文翻译：

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无处可藏：在季节性低流量期间，河道遮盖对于生活在沿海严酷的鳟鱼鳟鱼的重要性

通过其多种功能，避难所对于生活在河中的鱼类可能很重要，尤其是在季节性低流量或干旱等压力事件期间。沿海割喉鳟鱼Oncorhynchus clarkii clarkii是了解避难所重要性的理想研究生物。在季节性低流量期间，较低的水位限制了人们的庇护和移徙，鱼类的生存率低，捕食的风险也很高。在这种情况下，我们通过实地观察研究了掩盖使用的模式，并从关于半自然实验中掩盖使用的多个假设中测试了预测。巨石是鳟鱼在自然溪流中选择的主要遮盖物。鳟鱼在较深的水域中过度使用了掩体，他们在较浅的水域中选择了较大尺寸的掩体。鳟鱼表现出可塑性，可以在各种行为之间进行切换，隐蔽地掩藏和迁移为第一选择，然后进行分组，然后转移栖息地。缺乏觅食和生长表明，感知到的捕食威胁是行为的重要驱动因素，而不是觅食。移民也与覆盖物相关，较高的移民水平与较少的覆盖物可利用性相关联，揭示了通过移民在避难所和人口统计学之间的潜在联系。除了进食，其他行为的强度可能会根据避难所的可用性而增加或减少。总的来说，这项工作的发现表明，覆盖物可以与其他生活用水和鱼类的食物和空间基本资源一起被认为是至关重要的限制资源。