Fig 1.
Survey station in the fishways of Miyanaka Intake Dam.
Three types of fishways with different flow velocities and water depths are installed on the right bank side.
Fig 2.
Water sampling, developed in-vehicle unique filtration system, and storage of filter paper.
Table 1.
Sequences of primers used for PCR.
Fig 3.
Position and state of the temporary trap for catching fish.
Three traps were temporarily installed at the upstream ends of all fishways for one month each. Fish were caught in underwater net cages. The blue arrow indicates the flow direction.
Fig 4.
Results obtained from catch surveys in fish passages (number of species, number of P. altivelis populations, and other populations).
Table 2.
Number of species detected by metabarcoding and captured by survey from 2019 to 2022.
Fig 5.
Comparison of fish catch survey results and environmental DNA analysis results (2019–2022).
Fig 6.
Comparison of the number of fish species confirmed using environmental DNA surveys and capture surveys.
Environmental DNA survey results are the total for 2021 and 2022, and capture survey results are the total for 2012–2022. One species that was confirmed only through the environmental DNA survey is C. cuvieri, and the three species confirmed only through the capture survey are Tanakia lanceolata (past one individual), Rhodeus ocellatus (past five individuals), and Tribolodon nakamurai (past two individuals). The numbers of all of these fish were too small for confirmation.
Fig 7.
Comparison of environmental DNA survey results and capture survey results for each fishway.
(a) Case 1 and (b) Case 2.
Fig 8.
Verification of natural conditions indicated by environmental DNA at a specific time targeting four periods and number of fish species caught in each fishway.
(Ice: ice-harbor-type fishway; Stair: stair-type fishway; and Rock: rock-ramp-type fishway).
Fig 9.
Verification of natural conditions indicated by environmental DNA at a specific time targeting four periods and the five main types of fish caught.