Dams, weirs, and hydropower facilities are often cited as migratory barriers which impart significant reductions in fitness among migratory fish species. Even where upstream and downstream passage options are available, barrier passage can still often result in energetic or physical costs which compound delays or cause mortality. Past studies have identified variables associated with such fitness reductions, though few examine their effects in the context of the whole river scale. To this end, we assessed the migratory rates and downstream passage of radio‐tagged Atlantic salmon (Salmo salar) smolts through nine river sections (including two reservoir sections and one dammed section) along a 20 km stretch of river. Migration stoppages were not found to be elevated in reservoir or dammed sections, while migration rates were best described by physical river properties (width), biological traits (smolt total length), and seasonal variables (diel period) rather than anthropogenic factors. These results suggest the negative effect of reservoirs may primarily be due to their influence on river width and may be negligible when width is largely unaffected by an impoundment. Similarly, spilling water during fish migrations as a mitigative measure appears to make delays negligible. These conditions and actions may not completely marginalize the effect of dams, however, as a negative trend was still observed resulting from passage effects at the dam.

中文翻译：

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大西洋鲑鲑鱼迁徙速度与环境和人为因素的关系

大坝，堰和水力发电设施通常被认为是迁徙障碍，会大大降低迁徙鱼类的适应性。即使在有上游和下游通道选项的地方，障碍物通道仍然经常会导致精力或物质成本的增加，从而延误了延误或导致了死亡。过去的研究已经确定了与适宜度降低相关的变量，尽管很少有人在整个河流规模的背景下检验它们的影响。为此，我们评估了带有放射性标记的大西洋鲑鱼（Salmo salar）的迁移率和下游通道）沿着20公里长的河道穿越9条河段（包括2个水库段和1个坝段）。在水库或堤坝段中，迁移停滞没有发现增加，而迁移率最好用河流的物理特性（宽度），生物学特性（大烟总长度）和季节性变量（干旱期）而不是人为因素来描述。这些结果表明，水库的负面影响可能主要是由于它们对河流宽度的影响，而当宽度在很大程度上不受蓄水库的影响时，则可以忽略不计。同样，作为缓解措施，在鱼类迁徙期间洒水似乎可以将延误忽略不计。这些条件和行动可能不会完全边缘化水坝的影响，但是，