Climate change is altering the spatial and temporal patterns of temperature and discharge in rivers, which is expected to have implications for the life stages of anadromous fish using those rivers. We developed an individual-based model to track American Shad Alosa sapidissima offspring within a coarse template of spatially and temporally variable habitat conditions defined by a combination of temperature, river velocity, and prey availability models. We simulated spawning at each river kilometer along a 142-km reach of the Connecticut River on each day (April 1–August 31) to understand how spawning date and location drive larval recruitment differentially across years and decades (1993–2002 and 2007–2016). For both temperature and flow, interannual variation was large in comparison to interdecadal differences. Variation in simulated recruitment was best explained by a combination of season-specific spawning temperature and location along the course of the river. The greatest potential recruitment occurred during years in which June temperatures were relatively high. In years when June and July were warmer than average, maximum recruitment resulted from spawning taking place at the upstream portion of the modeled reach. Model scenarios (stationary or passive-drift larvae; and dams or no dams) had predictable effects. We assumed that the pools above dams had negative impacts on eggs and yolk-sac larvae that may have been deposited there. Allowing eggs and larvae to drift passively with the current reduced spatial differences in recruitment success among spawning sites relative to stationary eggs and larvae. Our results demonstrate the importance of spatiotemporal environmental heterogeneity for producing positive recruitment over the long term. In addition, our results suggest the importance of successful passage of spawners to historical spawning sites in the Connecticut River upstream of Vernon Dam, especially as conditions shift with climate change.

中文翻译：

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模拟大河中美洲鲥鱼幼体的招募

气候变化正在改变河流温度和流量的空间和时间模式，预计这将对使用这些河流的溯河鱼类的生命阶段产生影响。我们开发了一个基于个体的模型来跟踪美国 Shad Alosa sapidissima在由温度、河流流速和猎物可用性模型组合定义的空间和时间可变栖息地条件的粗模板中的后代。我们模拟了每天（4 月 1 日至 8 月 31 日）在康涅狄格河 142 公里范围内每条河流公里处的产卵，以了解产卵日期和位置如何在不同年份和几十年（1993-2002 和 2007-2016 ）。对于温度和流量，与年代际差异相比，年际变化较大。模拟补充的变化最好通过季节特定的产卵温度和河流沿线位置的组合来解释。最大的潜在招募发生在 6 月温度相对较高的年份。在 6 月和 7 月比平均温度高的年份，最大补充是由于在模拟河段的上游部分产卵。模型情景（静止或被动漂流幼虫；有水坝或无水坝）具有可预测的影响。我们假设水坝上方的水池对可能沉积在那里的卵和卵黄囊幼虫有负面影响。允许卵和幼虫被动漂移，当前产卵地点相对于静止卵和幼虫在募集成功方面的空间差异较小。我们的结果证明了时空环境异质性对于长期产生积极招募的重要性。此外，我们的研究结果表明，产卵者成功通过弗农大坝上游康涅狄格河历史产卵点的重要性，尤其是在条件随着气候变化而变化的情况下。