Shry Samuel, Harbicht Andrew, Forsberg Hanna, Nilsson Anders, Hellström Gustav, Österling Martin, Calles Olle
River Ecology and Management, Department of Environmental and Life Sciences, Karlstad University, Karlstad, Sweden.
Department of Fisheries and Oceans, Moncton, New Brunswick, Canada.
J Fish Biol. 2025 May;106(5):1440-1451. doi: 10.1111/jfb.15770. Epub 2024 May 9.
Migration is critical for life-cycle completion in diadromous fish species. River connectivity is vital in facilitating these large-scale movement events, but the extent of present-day river fragmentation can interfere with these migrations. Fish passage solutions (FPSs) are commonly implemented with the aim of improving river connectivity. In our study, we investigated the performance of two types of FPSs, spill regimes and complete dam removal, on Atlantic salmon (Salmo salar) smolt migrations. We used acoustic telemetry to monitor migration behavior and passage success of 120 wild smolts released in three different groups/sites: one group with two dams to pass to reach the river mouth, a second group with one dam to pass, and a control group without any barriers to pass (upstream of a recently removed hydroelectric dam). Smolt passage probabilities were similar for the two studied dams (87% and 86%) but showed variation in path choice, delay times, and loss rates. Passage success was influenced by several factors, such as body size, diel period, and water temperature, but not flow. Cumulative passage success to the river mouth was 61%, with most individuals being lost within lentic river stretches, either in the forebays of hydroelectric power stations or in naturally wide river stretches. Within the recently rehabilitated river sections (post dam removal), passage speeds were significantly faster than all other sections of the river (post-rehabilitation x¯ = 56.1 km/day) with significantly faster speeds compared to pre-rehabilitation (pre-x¯ = 28.0 km/day). Our findings provide valuable information on the benefits of dam removal and highlight the need for further rehabilitation measures in upriver reaches where barriers still affect downstream passage.
洄游对于溯河产卵鱼类完成生命周期至关重要。河流连通性对于促进这些大规模洄游活动至关重要，但当前河流破碎化的程度可能会干扰这些洄游。鱼类通道解决方案（FPSs）通常是为了改善河流连通性而实施的。在我们的研究中，我们调查了两种类型的FPSs，即溢流方式和完全拆除大坝，对大西洋鲑（Salmo salar）幼鱼洄游的性能。我们使用声学遥测技术监测了在三个不同组/地点释放的120只野生幼鱼的洄游行为和通过成功率：一组要通过两座大坝才能到达河口，第二组要通过一座大坝，还有一个对照组没有任何障碍物需要通过（在最近拆除的水电站大坝上游）。两个研究大坝的幼鱼通过概率相似（87%和86%），但在路径选择、延迟时间和损失率方面存在差异。通过成功率受几个因素影响，如体型、昼夜时段和水温，但不受流量影响。到达河口的累计通过成功率为61%，大多数个体在静水河段丢失，要么在水电站的前池，要么在自然宽阔的河段。在最近修复的河段（大坝拆除后），洄游速度明显快于河流的所有其他河段（修复后x¯ = 56.1 km/天），与修复前相比速度明显更快（修复前x¯ = 28.0 km/天）。我们的研究结果提供了关于拆除大坝益处的宝贵信息，并强调了在上游河段仍有障碍物影响下游通道的地方需要进一步采取修复措施。
