Variation of Japanese eel eDNA in sequentially changing conditions and in different sample volumes.

Environmental DNA (eDNA) surveys have been conducted to evaluate the distribution and abundance of Japanese eels. However, various environmental and biological factors may influence eDNA concentrations. An experiment was conducted using three water sample replicates (50, 100 and 200 ml) of the same group of eels in a tank that were exposed to sequential nonfeeding/feeding and low/high temperature conditions. Slightly higher concentrations occurred at higher temperature (22-23°C) with nonfeeding, and the highest concentrations occurred when feeding started even though it was in the lower temperature (16-17°C) condition, but sample volume had no effect.