Gnathopogon caerulescens is an endangered but commercially important fish in Lake Biwa, Japan. The population size of G. caerulescens has drastically reduced in the past decades, and there is a strong need to develop effective resource management frameworks for the sustainable use of this species. In the management of endangered species, it is important to monitor and grasp their distribution and abundance. Although catch-based methods have generally been employed for this purpose, these methods require more labor and time and can damage the populations of endangered species. In this study, we aimed to develop a rapid and non-invasive monitoring tool for G. caerulescens using an environmental DNA-based approach. We developed a real-time PCR assay that specifically detects and quantifies G. caerulescens DNA and applied the developed assay to monitor the concentrations of G. caerulescens DNA in water in Lake Biwa. The dynamics of G. caerulescens DNA concentrations well reproduced the main characteristics of life history of G. caerulescens, suggesting the promising use of environmental DNA-based methods for monitoring the distribution and abundance of this species.

Gnathopogon caerulescens是日本琵琶湖中一种濒临灭绝但具有重要商业价值的鱼类。G. caerulescens的种群规模在过去几十年中急剧减少，迫切需要为该物种的可持续利用开发有效的资源管理框架。在濒危物种的管理中，重要的是监测和掌握它们的分布和丰度。尽管为此目的通常采用基于捕获的方法，但这些方法需要更多的劳动和时间，并且可能损害濒危物种的种群。在这项研究中，我们旨在开发一种快速、无创的G. caerulescens监测工具使用基于环境 DNA 的方法。我们开发了一种实时 PCR 检测方法，专门检测和量化G. caerulescens DNA，并应用开发的检测方法来监测琵琶湖水中G. caerulescens DNA的浓度。G. caerulescens DNA 浓度的动态很好地再现了G. caerulescens生活史的主要特征，表明基于环境 DNA 的方法有希望用于监测该物种的分布和丰度。