Armstrong Jonathan B, Ward Eric J, Schindler Daniel E, Lisi Peter J
Department of Fisheries and Wildlife , Oregon State University , 104 Nash Hall, 2820 SW Campus Way, Corvallis, OR 97331, USA.
Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, 2725 Montlake Boulevard East, Seattle, WA 98112, USA.
Conserv Physiol. 2016 Oct 4;4(1):cow039. doi: 10.1093/conphys/cow039. eCollection 2016.
As climate change increases maximal water temperatures, behavioural thermoregulation may be crucial for the persistence of coldwater fishes, such as salmonids. Although myriad studies have documented behavioural thermoregulation in southern populations of salmonids, few if any have explored this phenomenon in northern populations, which are less likely to have an evolutionary history of heat stress, yet are predicted to experience substantial warming. Here, we treated a rare heat wave as a natural experiment to test whether wild sockeye salmon () at the northern extent of their primary range (60° latitude) can thermoregulate in response to abnormally high thermal conditions. We tagged adult sockeye salmon with temperature loggers as they staged in a lake epilimnion prior to spawning in small cold streams ( = 40 recovered loggers). As lake surface temperatures warmed to physiologically suboptimal levels (15-20°C), sockeye salmon thermoregulated by moving to tributary plumes or the lake metalimnion. A regression of fish body temperature against lake surface temperature indicated that fish moved to cooler waters when the epilimnion temperature exceeded ~12°C. A bioenergetics model suggested that the observed behaviour reduced daily metabolic costs by as much as ~50% during the warmest conditions (18-20°C). These results provide rare evidence of cool-seeking thermoregulation at the poleward extent of a species range, emphasizing the potential ubiquity of maximal temperature constraints and the functional significance of thermal heterogeneity for buffering poikilotherms from climate change.
随着气候变化使最高水温升高，行为体温调节对于冷水鱼类（如鲑科鱼类）的生存可能至关重要。尽管大量研究记录了鲑科鱼类南方种群的行为体温调节，但几乎没有研究探索过北方种群的这一现象，北方种群不太可能有热应激的进化史，但预计会经历显著变暖。在这里，我们将一次罕见的热浪视为一项自然实验，以测试在其主要分布范围北界（北纬60°）的野生红大马哈鱼（）是否能在异常高温条件下进行体温调节。在成年红大马哈鱼在小的冷溪流中产卵前在湖泊上层暂居时，我们用温度记录器对它们进行标记（共回收40个记录器）。随着湖面温度升至生理上次优水平（15 - 20°C），红大马哈鱼通过移动到支流羽流或湖泊温跃层进行体温调节。鱼体温度与湖面温度的回归分析表明，当湖泊上层水温超过约12°C时，鱼会游向较凉爽的水域。一个生物能量学模型表明，在最温暖的条件下（18 - 20°C），观察到的行为使每日代谢成本降低了多达约50%。这些结果提供了在物种分布范围极北地区寻求凉爽体温调节的罕见证据，强调了最高温度限制的潜在普遍性以及热异质性对于缓冲变温动物应对气候变化的功能重要性。
