Impacts on marine survival of Atlantic salmon Salmo salar include sea lice Lepeophtheirus salmonis infestation from coastal aquaculture, and ocean climate forcing. These effects may interact because infestation compromises smolt growth and body condition, and thus response to environmental conditions. We hypothesized that migrating smolts exposed to lice from salmon farms would show (i) reduced one sea-winter (1SW) returns to natal rivers and (ii) a shift in relationships between ocean climate and returns. Annual counts of 1SW fish were studied from ten rivers in Ireland, including five “control” systems without salmon aquaculture. Most counts showed a downward trend, consistent with declines in Atlantic salmon populations. Rivers with aquaculture showed lesser returns (mean 33%, range 19–46%) in years following high lice levels on nearby salmon farms. The level of likely lice pressure also modified how annual 1SW returns varied with ocean conditions. Returns to control rivers showed a weak negative relationship with the Atlantic Multi-decadal Oscillation (AMO) in the late summer (September) of the out-migrating year. This negative AMO effect became much stronger for fish migrating in low lice years but was not evident for high lice years. Smolts experiencing mild-to-moderate lice infestation may show greater sensitivity to ocean warming.

中文翻译：

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暴露于水产养殖海虱的野生大西洋鲑鱼显示海洋生存减少且对海洋气候的反应有所改变

对大西洋鲑鱼的生存海洋影响大西洋鲑包括海虱Lepeophtheirus鲑沿海水产养殖和海洋气候强迫的侵扰。这些影响可能会相互作用，因为侵扰会损害软体动物的生长和身体状况，进而影响环境状况。我们假设从鲑鱼养殖场迁移到暴露于虱子的软体动物将显示出（i）减少了一个冬季（1SW）回归到产河的回潮，以及（ii）海洋气候与回归之间的关系发生了转变。在爱尔兰的十条河流中研究了1SW鱼类的年度计数，包括五个没有鲑鱼养殖的“控制”系统。大多数数量呈下降趋势，与大西洋鲑鱼种群的减少相一致。由于附近鲑鱼养殖场的虱子水平高，水产养殖河流的年回报率较低（平均33％，范围19–46％）。可能的虱子压力水平也改变了年度1SW回报如何随海洋条件而变化。在迁出年份的夏末（9月），控制河流的回报与大西洋多年代际涛动（AMO）之间存在弱的负相关关系。在低虱子年中，这种负面的AMO效应对于鱼类迁移变得更加强烈，但在高虱子年中却不明显。经历轻度到中度虱子侵扰的软体动物可能对海洋变暖表现出更高的敏感性。