ABSTRACT: As a consequence of climate change and open net-pen salmon farming, wild Atlantic salmon Salmo salar are increasingly likely to encounter elevated temperatures and parasite abundances during their early marine migration. Such stressors can compromise fitness by diminishing liver energy stores and impairing cardiac muscle. To assess whether temperature and infestation by salmon lice Lepeophtheirus salmonis are important correlates of liver energy stores and cardiac muscle performance in juvenile salmon, we experimentally infested fish at 3 abundances of louse infestation (zero, low, and high) and 5 temperatures (10, 13, 16, 19, and 22°C). At the end of the experiment (i.e. when sea lice reached adulthood), we calculated the percent dry weight of the liver (%DWL; a proxy for liver energy stores) and cardiosomatic index (CSI; a proxy for cardiac muscle performance) of each fish and fitted 5 linear mixed-effects models to both of these responses. For both %DWL and CSI, the best-supported model included additive fixed effects for both infestation level and temperature. Our top models predicted that, relative to zero infestation, high infestation reduces %DWL by 5.7% (95% CI: 5.3-6.2%) and increases CSI by 15.9% (14.4-18.0%), and low infestation reduces %DWL by 2.6% (2.2-3.0%) and increases CSI by 7.8% (6.7-10.0%). Our work suggests that stressors associated with ocean warming and coastal salmon aquaculture can compromise wild salmon fitness through the impairment of vital organs.

中文翻译：

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气温升高和寄生海虱损害大西洋鲑幼鱼的内部器官

摘要：由于气候变化和开放式网箱鲑鱼养殖的结果，野生大西洋鲑Salmo salar在其早期海洋迁移期间越来越有可能遇到高温和寄生虫丰度。这样的压力源可以通过减少肝脏能量存储和损害心肌来损害健康。评估温度和鲑鱼虱子Lepeophtheirus鲑鱼的侵扰是幼鲑鱼肝能量存储和心肌功能的重要相关因素，我们在3种大量虱子侵扰（零，低和高）和5个温度（10、13、16、19和22°C）的实验中侵染了鱼类。在实验结束时（即当海虱成年时），我们计算了每个肝脏的干重百分比（％DWL；代表肝脏能量存储）和心动指数（CSI；代表心肌功能）鱼并为这两个响应拟合了5个线性混合效应模型。对于％DWL和CSI，最受支持的模型包括针对感染水平和温度的累加固定效应。我们的顶级模型预测，相对于零感染，高感染可将％DWL降低5.7％（95％CI：5.3-6.2％），并将CSI增加15.9％（14.4-18.0％），低度侵扰会使％DWL降低2.6％（2.2-3.0％），而CSI则提高7.8％（6.7-10.0％）。我们的工作表明，与海洋变暖和沿海鲑鱼养殖有关的压力源可以通过损害重要器官而损害野生鲑鱼的适应性。