Hatch timing in autumn-spawning stream salmonids is poorly understood in the subarctic region because snow cover prevents direct sampling of cryptic early life stages. Otolith micro-increment analysis was used to infer hatch dates of white-spotted charr Salvelinus leucomaenis (Pallas) and masu salmon Oncorhynchus masou (Brevoort) in a mainstem-tributary network in northern Japan. Accuracy and precision were validated by ageing hatchery individuals with known hatch date ranges. In July 2018, 93 wild young-of-the-year white-spotted charr and 81 masu salmon were collected and aged. Masu salmon hatched, on average, 24 days earlier (mean = February 8) than white-spotted charr (March 4), and hatch dates spanned a minimum of 2 months for each species. In masu salmon, hatch dates of individuals collected in the mainstem were nearly 3 weeks earlier than those in a tributary. This study provided knowledge on intra- and inter-specific variation in hatch timing of native salmonids in a subarctic stream network.

中文翻译：

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由耳石增量估计的河流网络中两种亚北极鲑鱼的孵化时间

在亚北极地区，人们对秋季产卵溪流鲑鱼的孵化时间知之甚少，因为积雪阻止了对神秘早期生命阶段的直接采样。耳石微增量分析用于推断白斑炭疽鱼Salvelinus leucomaenis (Pallas) 和马苏鲑鱼Oncorhynchus masou 的孵化日期(Brevoort) 在日本北部的一个干支流网络中。准确度和精密度由孵化日期范围已知的老龄孵化场个体验证。2018 年 7 月，采集并陈化了 93 条野生年幼白斑鱼和 81 条马苏鲑鱼。马苏鲑鱼的孵化时间平均比白斑鲑鱼（3 月 4 日）早 24 天（平均值 = 2 月 8 日），每个物种的孵化日期至少跨度为 2 个月。在马苏鲑鱼中，在主干中收集的个体的孵化日期比在支流中的个体早近 3 周。这项研究提供了有关亚北极河流网络中本地鲑鱼孵化时间的种内和种间变化的知识。