Worldwide, rivers are extensively fragmented by anthropogenic structures, reducing longitudinal connectivity, inhibiting migration and leading to severe declines in many fish populations, especially for diadromous species. However, few studies have determined the effects of annual differences in hydrology on catchment penetration past barriers to spawning habitats. We investigated the upstream spawning migration of 120 (n = 61 & 59) acoustic tagged river lamprey (Lampetra fluviatilis) across two contrasting (dry and wet) years in the River Yorkshire Ouse, England. Overall, significantly more lamprey reached spawning habitat (76% vs 39%) and penetrated significantly further upstream (median [km] from release, 53.9 vs 16.8) in the wet year than the dry year. Passage at weirs was almost exclusively during elevated river levels, which directly and collectively influenced catchment-wide distribution, especially in the dry year. Indeed, higher proportions entered two upper tributaries in the wet year (9.8% vs 27.1% and 9.8% vs 30.5%), due to increased passage efficiencies at the two main river weirs (60.5–87.5% and 54.5–83.8%), and reached assumed spawning locations 66.5% and 10.9% quicker. By contrast, there was no difference in numbers of lamprey entering, or time taken to arrive at assumed spawning location, in the two lower river tributaries between years. Our study supports the landscape-scale paradigm for ecosystem restoration because of the observed catchment-level effects of hydrology and barrier distribution on fish migration. Connectivity restoration for migratory fish should be implemented at a catchment scale, with planning incorporating spatial information regarding accessibility to key habitats to reap the largest gains.

在世界范围内，人类活动造成的河流广泛破碎，减少了纵向连通性，抑制了洄游，导致许多鱼类数量严重减少，尤其是产鱼鱼类。然而，很少有研究确定水文年度差异对流域渗透到产卵栖息地的障碍的影响。我们调查了 120 只（n = 61 和 59）声学标记的河七鳃鳗 ( Lampetra Fluviatilis)的上游产卵洄游）在英格兰约克郡乌斯河上度过了两个截然不同的年份（干旱和潮湿）。总体而言，与干旱年份相比，潮湿年份有更多的七鳃鳗到达产卵栖息地（76% vs 39%），并且明显更深入上游（距离释放的中位数[公里]，53.9 vs 16.8）。堰的通过几乎完全发生在河流水位升高的情况下，这直接和集体地影响了流域范围内的分布，特别是在干旱年份。事实上，由于两条主要河流堰的通过效率提高（60.5-87.5%和54.5-83.8%），在丰水年进入两条上游支流的比例更高（9.8% vs 27.1%和9.8% vs 30.5%），并且到达假定产卵地点的速度分别快了 66.5% 和 10.9%。相比之下，进入的七鳃鳗数量或到达假定产卵地点所需的时间没有差异，在两条河流下游支流之间。我们的研究支持生态系统恢复的景观尺度范式，因为观察到流域水文和屏障分布对鱼类迁徙的影响。洄游鱼类的连通性恢复应在流域范围内实施，并在规划中纳入有关关键栖息地可达性的空间信息，以获得最大收益。