Data from: Environmental DNA analysis as a non-invasive quantitative tool for reproductive migration of a threatened endemic fish in rivers

Quantitative information regarding reproduction is essential for
conserving endangered animals; however, some conventional quantitative
methods can be damaging to the target population and their habitats. In
the present study, the reproductive migration of a threatened endemic
fish, three-lips (Opsariichthys uncirostris uncirostris), was
non-invasively monitored by quantitative PCR of species-specific
environmental DNA (eDNA), the usefulness of which has been under-studied.
Water sampling and from-shore visual inspection were performed weekly
along a tributary of Lake Biwa (Japan), where adult fish seasonally
migrate upstream to reproduce as well as at lake sites near the river
mouth. Species-specific eDNA was collected at all locations at times when
the fish were visually observed and at certain sites where the fish were
not observed. Log-transformed individual counts from visual inspection
were positively correlated with log-transformed eDNA concentration in the
river sites, indicating that eDNA analysis can be a reliable quantitative
tool for fish abundance in rivers. Furthermore, distance from the lake did
not influence eDNA concentration, suggesting that eDNA transport by river
flow had a negligible effect on eDNA quantification. eDNA concentration
and individual counts both gradually increased from May–July, then both
decreased in August. Importantly, eDNA analysis showed that the fish
occupied more habitats in the peak reproductive season and stayed for
longer time at any given site. An additional underwater survey confirmed
unexpected eDNA detections as true positives. eDNA analysis has great
potential to quantitatively monitor reproductive fish migrations under
certain conditions.