Canadian Journal of Fisheries and Aquatic Sciences, Ahead of Print.
Accumulation of lipid reserves is considered important for the overwinter survival of many animals. Fish are thought to deplete lipids until they reach a critical minimum below which starvation mortality occurs, meaning that lipid-dependent selective overwinter mortality may be a strong selective pressure leading to life-history evolution favouring lipid accumulation and storage. Much of our current knowledge comes from either laboratory studies or field studies that are not well controlled, but rarely is overwinter survival directly estimated to evaluate selective mortality. Here, we studied patterns of lipid storage, overwinter lipid depletion, and subsequent survival of a single strain of rainbow trout (Oncorhynchus mykiss) stocked into experimental lakes that differed in productivity but experienced the same local winter conditions. Productive lakes produced trout with higher lipid content and steeper allometric slopes in contrast with trout in low food lakes; however, these field-based values were all substantially lower than those determined in the lab. Surviving trout from low productivity lakes emerged from winter in poor condition, close to the expected critical minimum needed for survival, in comparison with survivors from higher-productivity lakes. As expected, overwinter mortality was lipid-dependent, with fish in low food lakes nearing 90% mortality and about 60% mortality in high food lakes. Importantly, these estimates are higher than from laboratory (∼70%) and modelling studies (0% to 14%) for this species. These results, though from stocked populations, suggest winter mortality is an even stronger selective pressure than previously thought, creating a tight population bottleneck in young fish cohorts and likely promoting life-history strategies that favour energy storage at the expense of somatic growth.

中文翻译：

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实验性湖泊中虹鳟的秋季脂质储量，越冬脂质枯竭和冬季高死亡率

《加拿大渔业和水生科学杂志》，印刷前。
脂质储备的积累被认为对于许多动物的越冬存活很重要。人们认为鱼会消耗脂质，直到达到临界最小值为止，在该临界最小值以下发生饥饿，这意味着依赖脂质的选择性越冬死亡率可能是导致生命历史演变的强大选择性压力，有利于脂质的积累和储存。我们目前的很多知识都来自控制不佳的实验室研究或田野研究，但很少直接评估越冬存活率以评估选择性死亡率。在这里，我们研究了储存在实验湖泊中的生产力不同但经历了相同局部冬季条件的虹鳟（Oncorhynchus mykiss）单个菌株的脂质存储，越冬脂质消耗以及随后的存活模式。与低食湖泊中的鳟鱼相比，高产湖泊所生产的鳟鱼的脂质含量更高，斜率更陡。但是，这些基于字段的值都大大低于实验室中确定的值。低生产力湖泊的存活鳟鱼在冬季条件差时出现，与高生产力湖泊的存活者相比，接近预期的生存最低临界值。如预期的那样，越冬死亡率是脂质依赖性的，低食物湖泊中的鱼类死亡率接近90％，而高食物湖泊中的死亡率约为60％。重要的是，这些估计值高于该物种的实验室（〜70％）和模型研究（0％至14％）。这些结果尽管来自种群众多，但表明冬季死亡率是比以前认为的更大的选择压力，