Environmental DNA concentrations of Japanese eels in relation to habitat characteristics

The Japanese eel (Anguilla japonica), is listed as "Endangered" by the IUCN. Understanding eel riverine habitat is useful in considering conservation strategies. This study sought to determine the relationship between environmental DNA (eDNA) concentrations derived from Japanese eels, water quality, and river structure in three small rivers in Nagasaki, Japan. eDNA was detected at 14 of 15 sites (93%). The concentration of eDNA in brackish water was significantly higher than that in freshwater and was correlated with water depth. Eel occurrence throughout the river suggests a need to conserve a diversity of habitats.