School of Biology and Environmental Science and Earth Institute, University College Dublin, Dublin 4, Ireland; Area52 Research Group, School of Biology and Environmental Science and Earth Institute, University College Dublin, Dublin 4, Ireland.
UCD Dooge Centre for Water Resources Research, School of Civil Engineering and Earth Institute, University College Dublin, Dublin 4, Ireland.
Sci Total Environ. 2020 Jun 1;719:137215. doi: 10.1016/j.scitotenv.2020.137215. Epub 2020 Feb 8.
Knowledge of the location, physical attributes and impacts of obstacles on river connectivity is a requirement for any mitigating action aimed at restoring the connectivity of a river system. Here, we present a study that recorded the numbers and physical diversity of obstacles in 10 river catchments in Ireland, together with the impact these structures had on overall river connectivity. A total of 372 obstacles were recorded, 3 of these were dams, and the remainder were low-head weirs/sluices, obstacles associated with road or rail crossings of rivers and natural structures. The degree of fragmentation was estimated in each catchment by calculating obstacle density and the Dendritic Connectivity Index (DCI). DCI scores were calculated for 4 native Irish fish species with different life-histories, namely diadromous (Atlantic salmon, sea trout, European eel, sea lamprey) and potamodromous (brown trout). Obstacle density ranged between 1.2 and 0.02 obstacles/km of river. Six of the 10 catchments had at least one obstacle located on the mainstem river at least 5 km from its mouth/confluence. These 6 catchments typically had the lowest connectivity scores for diadromous species and ranged between 0.6 and 44.1 (a fully connected river would receive a maximum score of 100). While there was no significant correlation between obstacle density and the DCI score for diadromous fish, a significant negative correlation was detected between obstacle density and the DCI score for potamodromous brown trout. Here, we highlight the merit of these obstacle assessments and associated challenges for decision-making relating to prioritisation of obstacles for removal or modification.
了解河流连通性的位置、物理属性和障碍物的影响是任何旨在恢复河流系统连通性的缓解措施的要求。在这里，我们介绍了一项研究，该研究记录了爱尔兰 10 个流域中障碍物的数量和物理多样性，以及这些结构对整体河流连通性的影响。共记录了 372 个障碍物，其中 3 个是水坝，其余的是低水头堰/水闸、与河流和自然结构的道路或铁路交叉的障碍物。通过计算障碍物密度和树枝状连通指数（DCI），在每个流域估计了碎片化程度。为 4 种具有不同生活史的爱尔兰本地鱼类（洄游鱼类，如大西洋鲑鱼、海鳟、欧洲鳗鲡、海七鳃鳗；半洄游鱼类，如褐鳟）计算了 DCI 得分。障碍物密度范围为 1.2 至 0.02 个障碍物/公里的河流。10 个流域中有 6 个至少有一个障碍物位于干流至少 5 公里处的河流。这些 6 个流域通常具有最低的洄游鱼类连通性得分，范围在 0.6 到 44.1 之间（完全连通的河流将获得 100 分中的最高分）。虽然障碍物密度与洄游鱼类的 DCI 得分之间没有显著相关性，但在障碍物密度与半洄游褐鳟的 DCI 得分之间检测到显著的负相关。在这里，我们强调了这些障碍物评估及其与决策相关的挑战的优点，这些挑战涉及为移除或修改障碍物确定优先级。
