We developed the HoOS simulator (Hasty or Omniscient Shads) to assess how upstream migration and reproductive timings influence allis shad Alosa alosa (Linnaeus, 1758) temperature-dependent survival of early-life stages. We tested the influence of two reproductive timings depending on whether spawners can synchronize their spawning activity (i.e., referred to as “omniscient fish”) with optimal temperature for early-life stage survival, or simply spawn immediately after arriving on the spawning grounds (i.e., referred to as “hasty fish”). We computed the survival of early-life stages using an existing relationship that predicts the survival of allis shad from hatch to up to 14 days post-hatching according to the time series of daily water temperature at the spawning grounds. The early-stage survival rate was then calculated for each reproductive timing using a range of upstream migration speed while also considering physiological constraints to spawning adults on reproductive timing. Results indicated that the temperature-dependent survival of early-life stages relative to the migration timing by the adults was dome-shaped, confirming the hypothesis of an optimal period for reproduction across the reproductive season. The expected gain of the early-stage survival under the “omniscient” reproductive timing was highest for early arrivals of adults on the spawning grounds, lowest for intermediate arrivals, and was increasing for late arrivals. The HoOS simulator demonstrated that early and late arrivals of adults calculated as less favorable could be compensated by an “omniscient” reproductive timing. In contrast, for intermediate transit times, the two spawning timings performed the same. Our results provided modelling support that a good match of spawning activity with optimal thermal conditions is particularly crucial for the early arriving adults to maximize allis shad fitness-related outcomes (here early-stage temperature dependent survival), a causal relationship frequently claimed but rarely explored.

我们开发了 HoOS 模拟器（Hasty 或 Omniscient Shads）来评估上游迁移和繁殖时间如何影响 allis shad Alosa alosa(Linnaeus, 1758) 生命早期阶段的温度依赖性存活。我们测试了两种繁殖时间的影响，这取决于产卵者是否可以将它们的产卵活动（即，称为“全知鱼”）与早期生存阶段的最佳温度同步，或者只是在到达产卵场后立即产卵（即，简称“草鱼”）。我们使用现有关系计算早期生活阶段的存活率，该关系根据产卵场每日水温的时间序列预测从孵化到孵化后最多 14 天的鲱鱼的存活率。然后使用一系列上游迁移速度计算每个繁殖时间的早期存活率，同时还考虑到在繁殖时间产卵成虫的生理限制。结果表明，与成虫迁移时间相关的早期生命阶段的温度依赖性存活是圆顶形的，证实了整个生殖季节繁殖最佳时期的假设。在“全知”繁殖时间下，早期成鱼在产卵地的预期收益最高，中间到货的最低，而晚到的成鱼则增加。HoOS 模拟器表明，计算为不太有利的成年人的早到晚到可以通过“全知”生殖时间来补偿。相比之下，对于中间运输时间，两个产卵时间表现相同。