Predator effects on prey populations are determined by the number of prey consumed and effects on the traits of surviving prey. Yet, effects of predators on prey traits are rarely evaluated in field studies. We measured the effects of predators on energetic traits (consumption and growth rates) of juvenile Atlantic salmon (Salmo salar) in a large-scale field study. Salmon fry were released at 18 sites that encompassed a wide range in abundance of predatory slimy sculpin (Cottus cognatus). We sampled salmon after 21 and 140 days to measure salmon growth and estimate consumption using a mass-balance model of methylmercury accumulation. Salmon population density was reduced fivefold at sites with abundant sculpin. Over the early season, salmon consumed less where sculpin were abundant, suggesting that reduced foraging under predation risk contributed to predator-caused mortality. In contrast, over the late season, salmon grew more where sculpin were abundant, suggesting that compensatory growth at reduced salmon population density moderated predator-caused mortality. Predator effects on prey energetics can drive variation in survival and growth, with important consequences for population dynamics.

中文翻译：

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捕食者对幼年大西洋鲑鱼（Salmo salar）能量学影响的季节性变化

捕食者对猎物种群的影响取决于消耗的猎物数量和对幸存猎物特征的影响。然而，在实地研究中很少评估捕食者对猎物特征的影响。我们在一项大规模实地研究中测量了捕食者对大西洋鲑鱼幼鱼（Salmo salar）能量特性（消耗和生长率）的影响。鲑鱼苗在 18 个地点被释放，这些地点包括大量捕食性粘液杜鹃（Cottus cognatus）。我们在 21 天和 140 天后对鲑鱼进行采样，以测量鲑鱼的生长情况并使用甲基汞积累的质量平衡模型估算消耗量。在有丰富杜鹃花的地方，鲑鱼的种群密度减少了五倍。在早期的季节里，在杜鹃花丰富的地方，鲑鱼的消费量减少，表明在捕食风险下减少觅食会导致捕食者导致的死亡率。相比之下，在后期，三文鱼在杜鹃花丰富的地方生长得更多，这表明三文鱼种群密度降低时的补偿性生长减缓了捕食者引起的死亡率。捕食者对猎物能量的影响可以驱动生存和增长的变化，对种群动态产生重要影响。