Swimming and schooling data of golden shiners in variable water temperatures

Temperature is highly influential on the physiology and behaviour of ectotherms. In fish, temperature affects social interactions such as schooling behaviour, a common defence against predation. However, the effect of temperature on the ability of schooling fish to collectively respond to a predator is unknown. Here we used a loom stimulus to simulate an approaching predator that elicited a fleeing response in schooling fish over a range of water temperatures (9-29°C) and group sizes (1-16 fish). While speed and acceleration always exhibited a positive curvilinear response to temperature, the optimal temperature at which performance peaked was different during the predation threat versus when they were unperturbed. Similarly, group-level metrics were sensitive to temperature immediately after a loom stimulus but showed no response to temperature during unperturbed swimming. The time taken for fish to respond to the loom stimulus was minimal at 20°C. The proportion of fish that startled, during a loom, peaked at 13°C – around the same temperature at which speed and acceleration were maximum. Taken together, our results suggest that ectothermic fish may be able to compensate for their slower swim speeds at lower temperatures during unperturbed swimming by increasing their sensitivity to startle in response to a predation threat. More generally, we show that in ectotherms the qualitative and quantitative effect of temperature on a behavioural trait may be dependent on the context.

温度对变温动物（ectotherms）的生理与行为具有显著调控作用。在鱼类中，温度会影响诸如集群行为这类常见的反捕食社会互动行为。然而，温度对集群鱼类协同应对捕食者的能力的影响仍未明确。本研究使用loom刺激（loom stimulus）模拟逼近的捕食者，在水温范围9~29℃、群体规模1~16尾鱼的实验条件下，诱导集群鱼类产生逃逸反应。尽管游泳速度与加速度始终随温度呈正曲线型响应，但捕食威胁情境下与无干扰状态下，运动表现达到峰值的最适温度存在差异。与之类似，群体层面的各项指标在loom刺激后即刻对温度表现出敏感性，但在无干扰游泳状态下则不受温度调控。鱼类对loom刺激产生响应的耗时在20℃时达到最短。在loom刺激过程中，发生受惊逃逸的个体比例在13℃时达到峰值——这一温度与游泳速度和加速度达到最大值的温度基本一致。综合来看，本研究结果表明，变温鱼类可通过提升对捕食威胁的受惊逃逸敏感性，弥补无干扰游泳状态下低温环境中较慢的游泳速度。更广泛而言，本研究证实，在变温动物中，温度对行为性状的定性与定量影响可能取决于具体情境。