More than two thirds of large rivers worldwide are fragmented, threatening freshwater biodiversity, river integrity, and the services that freshwater ecosystems provide for human populations around the globe. In an effort to alleviate the impacts of barriers, engineered solutions have been developed, though with somewhat underwhelming results. River restoration, especially dam removal, is viewed as the optimal option though seldom the go-to approach. In this study, we evaluated the effects of a large restoration project (pseudo dam removal) in River Kolding, Southern Jutland, Denmark, via a before-after-control-impact (BACI) approach. Using a large dataset of electrofishing data from 74 sites (including downstream unaffected sites, reconnected sites and upstream regulated sites), we found that habitat connectivity was restored successfully, with a large increase in young-of-the-year brown trout (Salmo trutta) at reconnected sites, reaching similar densities to downstream (non-affected) sites. We further observed a decrease in length at reconnected sites, suggesting that natural spawning and rearing habitats were successfully restored too.

中文翻译：

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河流破碎化的集水规模效应：恢复连通性的案例研究。

全世界三分之二以上的大河支离破碎，威胁着淡水生物多样性，河流完整性以及淡水生态系统为全球人口提供的服务。为了减轻障碍的影响，已经开发了工程解决方案，尽管结果有些令人失望。尽管很少采用，但恢复河流，尤其是拆除大坝是最理想的选择。在这项研究中，我们通过控制后影响（BACI）方法评估了丹麦南日德兰半岛科灵河上的大型修复工程（拆除假大坝）的效果。使用来自74个地点（包括下游未受影响的地点，重新连接的地点和上游受管制的地点）的大型电钓鱼数据集，我们发现栖息地的连通性已成功恢复，重新连接的地点的年幼褐鳟（Salmo trutta）大量增加，达到与下游（未受影响）地点相似的密度。我们进一步观察到重新连接的地点的长度减少了，这表明自然产卵和饲养栖息地也得到了成功恢复。