Prey communities in the North Pacific Ocean have been disrupted by marine heatwaves, and reductions in forage fishes have had notable impacts on upper-trophic-level consumers. Little is known about the potential effects of a changing prey base for some commercially valuable fishes, such as Sablefish Anoplopoma fimbria. The objectives of this study were to evaluate temporal and age-based shifts in diets of juvenile Sablefish, with a focus on understanding their reliance on high-quality forage fishes. We collected Sablefish from a bay in Southeast Alaska over 2 years (2017–2019) during their first autumn (September–October; age 0), in late winter (March; age 1), and during their second summer (July; age 1). Pacific Herring Clupea pallasii constituted the majority of the Sablefish diet by weight (82.1%) and by frequency of occurrence (40.7%), with variation among months, years, and age-classes. Stable isotopes corroborated our interpretation of diet composition from stomach contents and indicated that age-0 Sablefish sampled in October 2017 relied on more depleted carbon sources than other groups, potentially explained by consumption of adult salmon carcasses. Significant relationships between stable isotope ratios and Sablefish length indicated that size-based diet composition differences were most prevalent during March and July. Sablefish exploited prey taxa of variable quality (0.02–5.3 kJ/g), but mean energy density of consumed prey differed little among years or months (3.62–4.48 kJ/g). Overall, 21% of stomachs sampled were empty, with the percentage of empty stomachs peaking in late winter (46%). Stomach content weights expressed as a percentage of body weight were highest in autumn 2018, when Pacific Herring comprised over 80% of the diets by weight. Consumption of high-energy prey, such as Pacific Herring, may contribute to rapid growth of Sablefish during the critical prewinter period. If strong Sablefish year-classes become more frequent with a warming ocean, they will require substantial prey resources to support their growth to adulthood.

中文翻译：

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幼鱼饮食成分和质量的时间和基于年龄的变化：来自胃内容物和稳定同位素的推论

北太平洋的猎物群落受到海洋热浪的干扰，饲料鱼类的减少对上营养级消费者产生了显着影响。对于某些具有商业价值的鱼类，如 Sablefish Anoplopoma fimbria，改变猎物基地的潜在影响知之甚少。本研究的目的是评估幼年黑貂鱼的饮食随时间和年龄的变化，重点是了解它们对优质饲料鱼的依赖。我们在 2 年（2017-2019 年）的第一个秋季（9 月至 10 岁；0 岁）、冬末（3 月；1 岁）和第二个夏季（7 月；1 岁）期间从阿拉斯加东南部的一个海湾收集了黑斑鱼）。太平洋鲱鲱pallasii按重量 (82.1%) 和出现频率 (40.7%) 构成 Sablefish 饮食的大部分，在月、年和年龄级别之间存在差异。稳定同位素证实了我们对胃内容物饮食成分的解释，并表明 2017 年 10 月采样的 0 岁黑斑鱼依赖比其他群体更多的枯竭碳源，这可能是由于食用了成年鲑鱼尸体所致。稳定同位素比率和黑貂鱼长度之间的显着关系表明，基于体型的饮食成分差异在 3 月和 7 月最为普遍。Sablefish 捕食质量不一的猎物类群 (0.02–5.3 kJ/g)，但消耗的猎物的平均能量密度在年或月之间差异不大 (3.62–4.48 kJ/g)。总体而言，21% 的采样胃是空的，空腹百分比在冬末达到顶峰（46%）。以体重百分比表示的胃内容重在 2018 年秋季最高，当时太平洋鲱鱼占饮食重量的 80% 以上。食用太平洋鲱鱼等高能量猎物可能有助于黑斑鱼在关键的冬季前快速生长。如果随着海洋变暖，强壮的 Sablefish 年级变得更加频繁，它们将需要大量的猎物资源来支持它们成长到成年。