The evolution of pesticide resistance has driven renewed interest in non-chemical pest controls in agriculture. Spatial manipulations (physical barriers and fallowing, for example) can be an effective method of prevention, but these too might impose selection and cause rapid adaptation in pests. In salmon aquaculture, various non-chemical approaches have emerged to combat parasitic salmon lice (Lepeophtheirus salmonis) – a major pest with clear signs of evolved chemical resistance. ‘Depth-based’ preventions, now widely implemented, reduce infestation rates by physically segregating salmon from lice in their infective copepodid stage occurring in surface waters. Copepodids distributed deeper in the water column, however, can bypass these barriers and infest farms. If swimming depth is a heritable trait, we may see rapid evolutionary shifts in response to widespread depth-based prevention. We collected lice from Norwegian salmon farms and assayed more than 11,250 of their laboratory-reared offspring across 37 families. The vertical distributions of copepodids were measured using experimental water columns pressurised to simulate conditions at 0, 5 and 10 m depths. We demonstrated that lice respond strongly to hydrostatic pressure: an increase in pressure doubled the number of lice that migrated to the top of columns. There was also a large effect of family on this response, with the percentage of lice ascending to the top of pressurised columns ranging from 17 to 79% across families. Families with a weak swimming response to pressure are expected to occur deeper in the water column and so be more likely to infest farms employing depth-based preventions. If this between-family variation reflects genetic variation, then the parasite population may have the capacity to adapt to preventative measures. Such adaptation would have important commercial and ecological implications.

农药抗性的演变重新激发了人们对农业中非化学害虫防治的兴趣。空间操纵（例如，物理障碍和休耕）可能是一种有效的预防方法，但这些也可能强加选择并导致害虫快速适应。在鲑鱼水产养殖中，出现了各种非化学方法来对抗寄生鲑鱼虱（Lepeophtheirus palmis) – 一种具有明显进化化学抗性迹象的主要害虫。“基于深度”的预防措施现已广泛实施，通过在地表水中发生的感染性桡足类阶段将鲑鱼与虱子进行物理隔离来降低感染率。然而，分布在水体深处的桡足类可以绕过这些障碍并感染农场。如果游泳深度是一种可遗传的特征，我们可能会看到响应广泛的基于深度的预防的快速进化变化。我们从挪威三文鱼养殖场收集了虱子，并对 37 个家庭的 11,250 多个实验室饲养的后代进行了分析。桡足类的垂直分布是使用实验水柱加压来模拟 0、5 和 10 m 深度的条件来测量的。我们证明虱子对静水压力反应强烈：压力的增加使迁移到柱子顶部的虱子数量增加了一倍。家庭对这种反应也有很大的影响，虱子上升到加压柱顶部的百分比在家庭中从 17% 到 79% 不等。对压力游泳反应较弱的家庭预计会出现在水体深处，因此更有可能感染采用基于深度的预防措施的农场。如果这种家族间变异反映了遗传变异，那么寄生虫种群可能有能力适应预防措施。这种适应将具有重要的商业和生态意义。虱子上升到加压柱顶部的百分比在各家庭中从 17% 到 79% 不等。对压力游泳反应较弱的家庭预计会出现在水体深处，因此更有可能感染采用基于深度的预防措施的农场。如果这种家族间变异反映了遗传变异，那么寄生虫种群可能有能力适应预防措施。这种适应将具有重要的商业和生态意义。虱子上升到加压柱顶部的百分比在家庭中从 17% 到 79% 不等。对压力游泳反应较弱的家庭预计会出现在水体深处，因此更有可能感染采用基于深度的预防措施的农场。如果这种家族间变异反映了遗传变异，那么寄生虫种群可能有能力适应预防措施。这种适应将具有重要的商业和生态意义。