Estimating the presence and abundance of non-native species in the early stage of invasion is important to prevent further spread of non-native species in aquatic systems. Environmental DNA (eDNA) methods have been applied for aquatic plants; however, it is still questionable on the accuracy of the eDNA methods for the detection and abundance estimation of aquatic plants in lotic systems. Here, we studied the invasive aquatic plant Egeria densa in the tributaries of the Gonokawa River in Japan to compare the E. densa detection rate of the eDNA method with that of the three sampling methods and examine the relationships of the eDNA flux to the upstream plant coverage, plant stem fragment flux, and plant tissue DNA flux of E. densa in the study sites on each season. Our results indicated that the eDNA method better detected the presence of E. densa in our study sites than other methods. The eDNA flux was directly related to the coverage rank and the plant tissue DNA flux in the study sites in both months. These results suggest that the eDNA methods have a potential as monitoring tool for early detection and relative abundance estimation of invasive aquatic plants in lotic systems.

估计入侵初期非本地物种的存在和丰富对于防止非本地物种在水生系统中的进一步传播很重要。环境DNA（eDNA）方法已应用于水生植物；然而，对于抽水系统中水生植物的检测和丰度估算，eDNA方法的准确性仍然值得怀疑。在这里，我们研究了入侵水生植物水蕴草在江之川在日本的支流比较E.致密的的eDNA方法与三个采样方法的检测率和检查的eDNA的关系通量到上游植物大肠杆菌的覆盖度，植物茎碎片通量和植物组织DNA通量在每个季节的研究地点。我们的结果表明，与其他方法相比，eDNA方法可以更好地检测我们研究场所中的大肠杆菌。在这两个月中，eDNA流量与研究地点的覆盖等级和植物组织DNA流量直接相关。这些结果表明，eDNA方法有潜力作为监测工具，用于早期检测和在抽水系统中对入侵性水生植物进行相对丰度估计。