ABSTRACT: Modelling potential impacts of salmon lice Lepeophtheirus salmonis on Atlantic salmon Salmo salar requires estimation of the levels that cause serious sub-lethal physiological impacts and direct mortality. Here we analysed results from existing laboratory experiments to identify 2 thresholds; the lower threshold (T1) estimates the level at which lice loads cause systemic sub-lethal effects on smolts likely to impact performance, and the upper threshold (T2) identifies the lice load causing direct mortality. T1 is an empirical value based on a catalogue of lice impacts according to impact type (superficial or systemic) and concentration, converted from a range of experiments. The onset of these indicators of welfare and behavioural impacts indicates T1 ≈ 0.08 lice g^-1 of host. T2 represents 50% probability of onset of mortality under laboratory conditions quantified using a dose-response curve based on data collated from studies where mortality has occurred or not at specified lice concentrations. T2 ≈ 0.24 lice g^-1 with a bootstrapped 95% confidence interval between 0.1 and 0.67 lice g^-1. These thresholds offer both an amending of the current approach to the management of lice concentrations on fish in the form of a sub-lethal welfare threshold and further evidence to support mortality-based lice thresholds already in use.

中文翻译：

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大西洋鲑鱼幼体上的鲑鱼虱负荷与福利减少和种群死亡率增加有关

摘要：模拟鲑鱼虱Lepeophtheirus salmonis对大西洋鲑鱼Salmo salar的潜在影响需要估计导致严重亚致死生理影响和直接死亡的水平。在这里，我们分析了现有实验室实验的结果，以确定 2 个阈值；较低的阈值 (T1) 估计虱子负荷对可能影响性能的小鲑鱼造成系统性亚致死效应的水平，而较高的阈值 (T2) 确定导致直接死亡的虱子负荷。T1 是一个经验值，基于根据影响类型（表面或全身）和浓度的虱子影响目录，从一系列实验转换而来。这些福利和行为影响指标的出现表明 T1 ≈ 0.08 lice g^-1的主机。T2 表示实验室条件下 50% 的死亡率发生概率，使用剂量反应曲线量化，该曲线基于从在特定虱子浓度下发生或未发生死亡的研究中收集的数据。T2 ≈ 0.24 lice g ^-1，自举 95% 置信区间在 0.1 和 0.67 lice g ^-1之间。这些阈值既以亚致死福利阈值的形式修正了当前管理鱼类虱子浓度的方法，也提供了支持已经使用的基于死亡率的虱子阈值的进一步证据。