Northern Rivers Institute, University of Aberdeen, Aberdeen AB24 3UF, UK.
Marine Scotland Science, Freshwater Fisheries Laboratory, Faskally, Pitlochry PH16 5LB, UK.
Sci Total Environ. 2019 Mar 10;655:557-566. doi: 10.1016/j.scitotenv.2018.11.263. Epub 2018 Nov 19.
Diadromous fish populations are strongly affected by in-stream barriers that cause river network fragmentation, constraining productivity or preventing completion of their lifecycle. Removal or reduction of barrier impacts is a restoration measure associated with unambiguous benefits. Management of barriers is therefore often prioritised above other restoration actions. Barrier management is prioritised at local and national scales depending on funding. However, barrier prioritisation is potentially sub-optimal because existing tools do not consider habitat quality. Furthermore, effects of partial barriers (those passable under certain conditions) are uncertain, depending on location and potential cumulative effects. A framework is presented for assessing effects of impassable manmade barriers (IMBs) on longitudinal river network connectivity (percentage of upstream habitat accessible from the river mouth) for Atlantic salmon across spatial scales, using Scotland as an example. The framework integrates juvenile habitat quality and network connectivity models to (1) provide information necessary for local and national prioritisation of barriers, and (2) assess potential effects of passable manmade barriers (PMBs) within a sensitivity framework. If only IMBs are considered, high levels of longitudinal connectivity are observed across most of Scotland's rivers. Barrier prioritisation is sensitive to habitat weighting: not accounting for habitat quality can lead to over- or underestimating the importance of IMBs. Prioritisation is also highly sensitive to the passability of PMBs: if passability drops to <97% (combined up- and downstream passability), the mean effect of PMBs becomes greater than IMBs at the national level. Moreover, impacts on catchment connectivity, and thus production (number of juvenile salmon produced by the river), could be severe, suggesting a better understanding of the passability of PMBs is important for future management of migration barriers. The presented framework can be transferred to other catchments, regions, or countries where necessary data are available, making it a valuable tool to the broader restoration community.
洄游鱼类种群受到河流网络破碎化的强烈影响，这些破碎化是由河流中的障碍物造成的，限制了生产力或阻止了它们生命周期的完成。障碍物的移除或减少影响是一种与明确利益相关的恢复措施。因此，障碍物的管理通常优先于其他恢复措施。根据资金情况，障碍物的管理在地方和国家层面上被优先考虑。然而，障碍物的优先级划分可能并不理想，因为现有的工具没有考虑到栖息地质量。此外，部分障碍物（在某些条件下可通行的障碍物）的影响是不确定的，这取决于位置和潜在的累积效应。本文提出了一个框架，用于评估不可通行的人为障碍物（IMBs）对大西洋鲑鱼在空间尺度上的纵向河流网络连通性（从河口可到达上游栖息地的比例）的影响，以苏格兰为例。该框架整合了幼鱼栖息地质量和网络连通性模型，（1）为地方和国家的障碍物优先级划分提供必要信息，（2）在敏感性框架内评估可通行的人为障碍物（PMBs）的潜在影响。如果只考虑 IMBs，苏格兰大部分河流的纵向连通性都很高。障碍物的优先级划分对栖息地权重敏感：不考虑栖息地质量可能导致对 IMBs 的重要性过高或过低估计。优先级划分也对 PMBs 的可通行性高度敏感：如果可通行性下降到<97%（上下游可通行性之和），则 PMBs 的平均影响在国家层面上大于 IMBs。此外，对流域连通性的影响，以及因此对产量（由河流产生的幼鲑数量）的影响可能是严重的，这表明更好地理解 PMBs 的可通行性对于未来的洄游障碍管理非常重要。在必要数据可用的情况下，该框架可以转移到其他流域、地区或国家，使其成为更广泛的恢复社区的宝贵工具。
