Environmental DNA to track endangered Gobiobotia naktongensis: Assessment of distribution and habitat requirements.

Because of their noninvasive nature and high detection sensitivity, eDNA-based aquatic ecosystem surveys are useful for monitoring rare, elusive indicator species. Advancements in statistical techniques have expanded their use beyond simple population tracking to predict potential habitats based on the environmental conditions of sites detected eDNA. This study used species-specific molecular marker and targeted qPCR techniques to assess the distribution and habitat requirements of the endangered Gobiobotia naktongensis, a flagship fish species in Korean sandy river systems with increased public interest related to habitat restoration evaluations associated with dam construction. As a small and sand-burrowing species, G. naktongensis is difficult to identify using traditional sampling methods as its population size has declined because of the construction and operation of dams. However, eDNA investigations have detected genes from the species throughout the year, enabling the identification of stable population sites by comparing with those of historical sampling records. Logistic regression analysis of G. naktongensis eDNA absence/presence and environmental factors revealed that its habitat preferences are closely associated with streambed substrate structure, water quality, and food source diversity. eDNA analytical techniques are being actively used for species that are globally endangered and whose rarity makes population monitoring challenging. eDNA-based surveys are promising for species with small population sizes and species-specific ecological traits (e.g., benthic or sand-burrowing species), which have been limited in quantitative research approaches because of the low occurrence of eDNA in the water, because these methods can yield meaningful results with qualitative data alone.