Dam-mediated biological invasions are a serious problem all over the world. Once established in reservoirs, the invasive species have catastrophic impacts on the river ecosystems downstream, and thus, rapid monitoring of invasive species is an urgent issue for the effective removal of them and the conservation management of native ecosystems. Here, we verified the utility of environmental DNA (eDNA) analysis as a tool to effectively monitor three invasive fish species (bluegill, largemouth bass, and smallmouth bass) in reservoirs using multiplex real-time PCR. First, to determine the optimal sampling location and season to detect eDNA from these species, we analyzed the eDNA in water samples from shore and offshore sites in three reservoirs all year around. We found that eDNA detection rates either did not differ between sampling locations or were higher for shore than offshore sites. In addition, eDNA detection rates were higher in spring (breeding season of target species) and/or summer than winter. Second, we extensively surveyed the distribution of the three species in 30 reservoirs in Japan using eDNA analysis. Consequently, a single eDNA-based surveillance in summer allowed to match approximately 90% of the presence/absence of the invasive fish species known from 27 yr of administrative capture-based surveillances. Given these results, we recommend collecting the replicated water samples from shore sites in summer or the breeding season for the effective detection of invasive fish eDNA in reservoirs. Our eDNA assays with multiplex real-time PCR enable the rapid and sensitive monitoring of invasive fish distribution in reservoirs.

中文翻译：

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环境 DNA 分析在有效监测水库入侵鱼类中的效用

大坝介导的生物入侵是全世界的一个严重问题。入侵物种一旦进入水库，就会对下游河流生态系统造成灾难性影响，因此，快速监测入侵物种是有效清除入侵物种和本地生态系统保护管理的紧迫问题。在这里，我们验证了环境 DNA (eDNA) 分析作为使用多重实时 PCR 有效监测水库中三种入侵鱼类（蓝鳃鱼、大嘴黑鲈和小嘴黑鲈）的工具的效用。首先，为了确定检测这些物种 eDNA 的最佳采样位置和季节，我们全年分析了来自三个水库的岸边和近海地点的水样中的 eDNA。我们发现 eDNA 检测率要么在采样地点之间没有差异，要么在岸上高于离岸地点。此外，春季（目标物种的繁殖季节）和/或夏季的 eDNA 检测率高于冬季。其次，我们使用 eDNA 分析广泛调查了日本 30 个水库中这三个物种的分布。因此，夏季的一次基于 eDNA 的监测可以匹配 27 年基于捕获的行政监测中已知的入侵鱼类物种的存在/不存在的大约 90%。鉴于这些结果，我们建议在夏季或繁殖季节从岸边收集重复的水样，以有效检测水库中的入侵鱼类 eDNA。