ABSTRACT: Salmon lice Lepeophtheirus salmonis from aquaculture can cause negative impacts on sea trout Salmo trutta and other wild salmonids. Long-term records from 5 Irish rivers were used to explore relationships between annual sea trout runs and estimated total number of lice on nearby salmon farms. It was hypothesised that local environmental conditions may result in system-specific differences in realised louse pressure on sea trout. Louse count was thus tested as an absolute number and as a relative pressure, i.e. standardised by farm. When the standardised total number of mobile lice on a given salmon farm in April was above baseline level (50^th percentile of observed annual values on that farm), there was a high probability of a below-average sea trout run in the local river. Absolute louse counts did not show an important effect on runs. This finding suggests that salmon farm louse production in spring can have a strong system-specific regulating effect on wild sea trout populations. Total number of lice on a farm was most strongly driven by changes in individual infestation rate, with a lesser effect of stocking density. Thresholds for number of mobile lice per farmed salmon required to maintain total louse count below the baseline varied with stocking density and among systems: greater density required lower infestation rate. Regulations relying on a generic louse threshold to trigger treatment are not sufficient to protect sea trout populations—stocking density and site characteristics must be considered to evaluate system-specific infestation pressure and impacts on wild salmonids.

中文翻译：

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鲑鱼养殖场特定系统的鲑鱼虱侵染阈值，以尽量减少对野生海鳟种群的影响

摘要：来自水产养殖的鲑鱼虱Lepeophtheirus Salmonis会对海鳟Salmo trutta和其他野生鲑鱼造成负面影响。来自 5 条爱尔兰河流的长期记录被用于探索年度海鳟鱼数量与附近鲑鱼养殖场估计的虱子总数之间的关系。据推测，当地的环境条件可能会导致对海鳟的虱子压力的系统特定差异。因此，虱子计数作为绝对数量和相对压力进行测试，即按农场标准化。当特定鲑鱼养殖场 4 月份的标准化移动虱子总数高于基线水平时（^第50在该养殖场观测到的年度值的百分位数），当地河流中的海鳟鱼很可能低于平均水平。绝对虱子计数没有显示出对运行的重要影响。这一发现表明，春季鲑鱼养殖场虱生产对野生海鳟种群具有很强的系统特异性调节作用。一个农场的虱子总数受个体侵染率变化的影响最大，饲养密度的影响较小。将虱子总数保持在基线以下所需的每条养殖鲑鱼的移动虱子数量阈值因放养密度和系统而异：密度越大，侵染率越低。