Thermal delousing has become the most applied method for treatment against salmon lice. However, the temperature range used is strongly aversive for salmonids, and the method is associated with increased mortality. Treatment temperature × duration combinations should be tailored to maximise delousing efficiency and minimize welfare impacts on the host fish. We tested the detachment rate of sessile, pre-adult and adult male and female salmon lice (Lepeophtheirus salmonis) as a function of ambient temperature (11–16 °C), exposure temperature (28–36 °C), and exposure duration (0–120 s). Dead Atlantic salmon (Salmo salar) hosts were used to avoid negative fish welfare and detachment of lice due to fish behaviour. Within the range tested, higher exposure temperatures were associated with higher detachment rates among pre-adult and adult lice, while no sessile lice detached at any temperature. Moreover, no treatment combination detached 100% of lice of any stage, and at 28 °C, detachment of adult females was not significantly different from control levels. Most detachments occurred within the first 30 s of exposure. We conclude that for a given delousing efficiency, lower temperatures must be compensated for by considerably longer exposure durations. This may be a higher risk for the welfare of the host fish than higher temperatures and shorter exposure durations.

热除虱已成为治疗鲑鱼虱最常用的方法。然而，所使用的温度范围对鲑鱼非常不利，并且该方法与死亡率增加有关。应调整处理温度×持续时间的组合，以最大限度地提高除虫效率并最大限度地减少对寄主鱼的福利影响。我们测试了无柄、成年前和成年雄性和雌性鲑鱼虱 ( Lepeophtheirus Salmonis ) 的脱离率与环境温度 (11-16 °C)、暴露温度 (28-36 °C) 和暴露时间 ( 0-120 秒）。死大西洋鲑鱼 ( Salmo salar) 宿主用于避免因鱼类行为而导致的负面鱼类福利和虱子脱落。在测试范围内，较高的暴露温度与成年前虱子和成年虱子的较高分离率相关，而在任何温度下都没有无柄虱子分离。此外，没有任何处理组合可以 100% 分离任何阶段的虱子，并且在 28°C 时，成年雌性虱子的分离与对照水平没有显着差异。大多数分离发生在曝光的前 30 秒内。我们得出结论，对于给定的除螨效率，较低的温度必须通过相当长的暴露时间来补偿。与更高的温度和更短的暴露时间相比，这可能对宿主鱼的福利造成更高的风险。