McGuire, Brigid, Biology, Bucknell University, 701 Moore Avenue C7890, Lewisburg, Pennsylvania, 17837, 07933, email@example.com; Takahashi, Mizuki, , Biology, Animal Behavior, Bucknell University, 701 Moore Avenue, Lewisburg, Pennsylvania, 17837, firstname.lastname@example.org.
The Japanese giant salamander (Andrias japonicus) is currently listed as Vulnerable by both the International Union for Conservation of Nature and the Japanese Ministry of the Environment, with its population continuing to decline. One of the major threats is human-made dams, which cause habitat fragmentations within a watershed, making isolated populations even more vulnerable to local extinction. The aim of this study is to characterize the distribution of A. japonicus in the upstream tributaries that have been disconnected from the main river stems, the known habitats for this species, for over 40 years by three large hydroelectric dams in Hyogo Prefecture, Japan, using environmental DNA (eDNA). Environmental DNA surveys are non-invasive (do not disturb animals or their habitats) and much more efficient in detecting the presence of the target species than traditional field surveys. During summers 2021, 2022, and 2023, we collected 73 total water samples from 16 different tributaries that feed into the three different dams (Kurokawa Dam: 23 samples from 6 tributaries; Tataragi Dam: 21 samples from 5 tributaries; Ikuno Dam: 29 samples from 5 tributaries). We conducted water filtration and DNA extraction on site and brought the extracted environmental DNA to Bucknell University where we ran quantitative PCR to detect the presence and to estimate the concentrations of A. japonicus eDNA in each site. We obtained A. japonicus liver tissue samples from San Antonio Zoo to make DNA standards (serial dilutions from 10-1 to 10-8 ng/µL). Although we did not see any salamanders during our sampling, our results show that there are 13 out of 23 eDNA positive sites for Kurokawa Dam tributaries, one out of 21 eDNA positive sites for Tataragi Dam tributaries, and 10 out of 29 eDNA positive sites for Ikuno Dam tributaries. We are still analyzing two more tributaries from Ikuno Dam. These results suggest that giant salamanders have persisted in those isolated habitats over several decades. Given the condition of many tributaries, their long-term survivability is questionable, begging for a conservation action plan.
Japanese giant salamander, environmental DNA, hydroelectric dams, habitat fragmentation