Understanding juvenile salmonid habitat requirements is critical for their effective management, but little is known about these requirements in lowland rivers, which include important but unique salmonid habitats. We compared the relative influence of in‐stream Ranunculus cover, water depth, prey abundance, distance upstream and two previously unexplored factors (water velocity heterogeneity and site colonisation potential) on summer densities of juvenile Atlantic salmon and brown trout. We applied electrofishing, habitat surveys and macroinvertebrate kick sampling, and calculated the site colonisation potential from salmon redd surveys across 18–22 sites in a lowland river in 2015–2017. Due to a recruitment crash in 2016, models including and excluding this unusual year were explored. Excluding 2016 data, juvenile salmon densities showed a positive association with Ranunculus cover and numbers of nearby upstream redds, and a negative association with distance upstream from the tidal limit. Trout densities were positively associated with velocity heterogeneity, indicating a potential indirect influence of Ranunculus mediated by water velocity. When including 2016, year had the largest effect on densities of both species, highlighting the impact of the recruitment failure. These findings uncover interspecific differences in the habitat requirements of juvenile salmonids in lowland rivers. Velocity heterogeneity and site colonisation potential had high explanatory power, highlighting that they should be considered in future studies of habitat use. These findings demonstrate that temporal replication and recruitment dynamics are important considerations when exploring species–habitat associations. We discuss potential management implications and argue that Ranunculus cover could be an important management tool in conservation of lowland salmonids.

中文翻译：

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高于海拔：低地河流栖息地的特征与大西洋鲑幼鱼（Salmo salar）和鳟鳟（S. trutta）的密度有关

了解少年鲑鱼栖息地的要求对于有效管理至关重要，但对于低地河流的这些要求知之甚少，其中包括重要但独特的鲑鱼栖息地。我们比较了河内毛an属的相对影响大西洋鲑和鳟鱼夏季密度的覆盖率，水深，猎物丰富度，上游距离和两个以前未曾探索的因素（水速异质性和定植点的潜力）。我们应用了电捕鱼，栖息地调查和大型无脊椎动物取样，并从2015-2017年在低地河流中的18-22个地点进行鲑鱼红化调查，计算了该地点的定殖潜力。由于2016年的招募失败，我们研究了包括和排除这一不寻常年份的模型。除2016年数据外，少年鲑鱼密度与毛an属呈正相关附近的上游冲积的数量和数量，以及与潮汐极限上游的距离呈负相关。鳟鱼密度与速度异质性呈正相关，表明毛an属有潜在的间接影响由水速度介导。当包括2016年时，年份对两个物种的密度影响最大，突出了招募失败的影响。这些发现揭示了低地河流中幼鲑鱼栖息地需求的种间差异。速度异质性和位点定殖潜力具有很高的解释力，突显了在未来的生境利用研究中应考虑它们。这些发现表明，在探索物种与栖息地的关联时，时间复制和募集动态是重要的考虑因素。我们讨论了潜在的管理含义，并认为毛an属植物的覆盖可能是保护低地鲑鱼的重要管理工具。