Salmon louse Lepeophtheirus salmonis, a key parasite of salmonids, is managed by multiple methods at both salmon farmand ecosystem-scale that are informed by an understanding of the abundance and distribution of the infective, planktonic stage of the lice. Dispersal modelling using hydrodynamic models relies on accurately estimating larval depth and how environmental variables modify distributions. Larval responses to temperature could modify dispersal distances by altering their depth in the water column and thus exposure to depth-dependent oceanographic processes and the duration of their temperature-dependent development. Using column experiments, we tested how L. salmonis nauplii and copepodids responded to different thermoclines by establishing a bottom layer of 12°C with an overlaying layer varying from 6 to 18°C in 2°C steps. Nauplii moved upwards in high proportions and aggregated in the surface layer when the overlying layer was 10°C or cooler. In contrast, nauplii moved downwards and aggregated at the thermocline when the overlying layer exceeded 12°C. Temperature did not influence the vertical distribution of copepodids. When nauplii behaviour towards temperature was integrated into a dispersal model, dispersal distances increased. Temperature should be considered when calculating depth distributions. Further, nauplii and copepodids behave differently and should be configured separately in dispersal models.

中文翻译：

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温跃层对鲑鱼虱幼虫垂直分布的影响

三文鱼虱 Lepeophtheirus Salmonis 是鲑科动物的一种主要寄生虫，在鲑鱼养殖场和生态系统范围内通过多种方法进行管理，这些方法是通过了解虱子感染性浮游阶段的丰度和分布而获得的。使用流体动力学模型的扩散建模依赖于准确估计幼虫深度以及环境变量如何修改分布。幼虫对温度的反应可以通过改变它们在水体中的深度来改变扩散距离，从而暴露于依赖于深度的海洋过程及其依赖于温度的发展的持续时间。我们使用柱状实验测试了鲑鱼无节幼体和桡足类动物如何通过建立 12°C 的底层和以 2°C 的步长从 6°C 变化到 18°C 的覆盖层来测试不同的温跃层。当上覆层温度为 10°C 或更低时，无节幼体以高比例向上移动并聚集在表层。相反，当上覆层超过 12°C 时，无节幼体向下移动并在温跃层处聚集。温度对桡足类的垂直分布没有影响。当无节幼体对温度的行为被整合到扩散模型中时，扩散距离增加。计算深度分布时应考虑温度。此外，无节幼体和桡足类的行为不同，应在分散模型中单独配置。温度对桡足类的垂直分布没有影响。当无节幼体对温度的行为被整合到扩散模型中时，扩散距离增加。计算深度分布时应考虑温度。此外，无节幼体和桡足类的行为不同，应在分散模型中单独配置。温度对桡足类的垂直分布没有影响。当无节幼体对温度的行为被整合到扩散模型中时，扩散距离增加。计算深度分布时应考虑温度。此外，无节幼体和桡足类的行为不同，应在分散模型中单独配置。