Anthropogenic influences, including climate change, are increasing river temperatures in northern and temperate regions and threatening the thermal habitats of native salmonids. When river temperatures exceed the tolerance levels of brook trout and Atlantic salmon, individuals exhibit behavioural thermoregulation by seeking out cold‐water refugia – often created by tributaries and groundwater discharge. Thermal infrared (TIR) imagery was used to map cold‐water anomalies along a 53 km reach of the Cains River, New Brunswick. Trout and salmon parr did not use all identified thermal anomalies as refugia during higher river temperature periods (>21°C). Most small‐bodied trout (8–30 cm) were observed in 80% of the thermal anomalies sampled. Large‐bodied trout (>35 cm) required a more specific set of physical habitat conditions for suitable refugia, that is, 100% of observed large trout used 30% of the anomalies sampled and required water depths >65 cm within or adjacent to the anomaly. Densities of trout were significantly higher within anomalies compared with areas of ambient river temperature. Salmon parr were less aligned with thermal anomalies at the observed temperatures, that is, 59% were found in 65% of the sampled anomalies; and densities were not significantly different within/ outside anomalies. Salmon parr appeared to aggregate at 27°C, and after several events over 27°C variability in aggregation behaviour was observed – some fish aggregated at 25°C, others did not. We stipulate this is due to variances of thermal fatigue. Habitat suitability curves were developed for velocity, temperature, depth, substrate, and deep water availability to characterize conditions preferred by fish during high‐temperature events. These findings are useful for managers as our climate warms, and can potentially be used as a tool to help conserve and enhance thermal refugia for brook trout and Atlantic salmon in similar systems.

中文翻译：

---

表征河道高温下溪鳟（Salvelinus fontinalis）和大西洋鲑（Salmo salar）的物理生境偏好和热避难所占用

人为因素的影响，包括气候变化，正在使北部和温带地区的河流温度升高，并威胁到本地鲑鱼的热生境。当河流温度超过鳟鱼和大西洋鲑的耐受水平时，人们会通过寻找冷水避难所表现出行为上的温度调节，这通常是由支流和地下水排放造成的。热红外（TIR）图像用于绘制新不伦瑞克省Cains河沿线53公里处的冷水异常图。在较高的河水温度（> 21°C）期间，鳟鱼和鲑鱼parr没有将所有已识别的热异常用作避难所。在80％的热异常中，观察到大多数小鳟鱼（8–30厘米）。大鳟鱼（> 35厘米）需要一组更具体的物理栖息地条件以进行适当的避难所，即100％的观察到的大鳟鱼使用了30％的异常采样，并且异常内部或邻近区域的水深> 65厘米。与环境河流温度区域相比，异常区域内的鳟鱼密度明显更高。在观察到的温度下，鲑鱼parr与热异常的一致性较差，也就是说，在65％的采样异常中发现59％。内部和外部异常的密度没有显着差异。鲑鱼parr似乎在27°C聚集，在超过27°C的数个事件之后，观察到聚集行为的变化–一些鱼在25°C聚集，而另一些则没有。我们规定这是由于热疲劳的差异。针对速度，温度，深度，底物和深水可用性，以表征高温事件中鱼类偏爱的条件。这些发现对我们的气候变暖的管理者很有用，并有可能被用作在类似系统中保护和提高溪鳟和大西洋鲑热避难所的工具。