Abstract Predators not only have direct impact on biomass but also indirect, non-consumptive effects on the behavior their prey organisms. A characteristic response of zooplankton in aquatic ecosystems is predator avoidance by diel vertical migration (DVM), a behavior which is well studied on the population level. A wide range of behavioral diversity and plasticity has been observed both between- as well as within-species and, hence, investigating predator–prey interactions at the individual level seems therefore essential for a better understanding of zooplankton dynamics. Here we applied an underwater imaging instrument, the video plankton recorder (VPR), which allows the non-invasive investigation of individual, diel adaptive behavior of zooplankton in response to predators in the natural oceanic environment, providing a finely resolved and continuous documentation of the organisms’ vertical distribution. Combing observations of copepod individuals observed with the VPR and hydroacoustic estimates of predatory fish biomass, we here show (i) a small-scale DVM of ovigerous Pseudocalanus acuspes females in response to its main predators, (ii) in-situ observations of a direct short-term reaction of the prey to the arrival of the predator and (iii) in-situ evidence of pronounced individual variation in this adaptive behavior with potentially strong effects on individual performance and ecosystem functioning.

中文翻译：

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捕食风险触发波罗的海桡足类小规模行为

摘要 捕食者不仅对生物量有直接影响，而且对其猎物生物的行为也有间接的、非消耗性的影响。浮游动物在水生生态系统中的一个特征反应是通过垂直迁移（DVM）来避免捕食者，这种行为在种群水平上得到了很好的研究。在物种之间和物种内都观察到了广泛的行为多样性和可塑性，因此，在个体水平上研究捕食者-猎物的相互作用似乎对于更好地了解浮游动物动态至关重要。在这里，我们应用了一种水下成像仪器，即视频浮游生物记录仪 (VPR)，它可以对浮游动物在自然海洋环境中对捕食者的反应进行非侵入性调查，研究浮游动物的个体适应行为，提供有机体垂直分布的精细解析和连续记录。结合使用 VPR 和捕食性鱼类生物量的水声估计观察到的桡足类个体的观察结果，我们在这里展示了 (i) 产卵 Pseudocalanus acuspes 雌性对其主要捕食者的反应的小规模 DVM，(ii) 直接的原位观察猎物对捕食者到来的短期反应，以及 (iii) 这种适应性行为中明显的个体变异的原位证据，对个体表现和生态系统功能有潜在的强烈影响。