Effectiveness of New Rock-Ramp Fishway at Miyanaka Intake Dam Compared with Existing Large and Small Stair-Type Fishways

Abstract

The migration of fish is influenced by the unique environmental characteristics of the destination and migratory habitat preferences. There are three fishways in Miyanaka Intake Dam. The rock-ramp fishway was newly established in 2012, creating an environment with different flow velocities and water depths. The purpose of this study was to investigate the effectiveness of the new rock-ramp fishway for native fish through two surveys. In the first survey, traps were installed during the survey period in all three fishways and all fish were caught. The run-up environment was quantified by measuring the flow velocity. In the second survey, fish were caught by spectrum methods upstream and downstream from the dam. It was found that bottom-dwelling fish and swimming fish not bound to the bottom with low migration abilities used the rock-ramp fishway for migration and as a habitat. After the new rock-ramp fishway was built, catches increased upstream from the dam. Further, the rock-ramp fishway is a potential habitat for certain species, such as Cottus pollux. As this is the first study to demonstrate the effectiveness of rock-ramp fishways, the research results are expected to be valuable to fishery managers and those planning river engineering projects.

Preferential behavior of Tribolodon hakonensis for fishways according to biological characteristics

“…However, a permit from the governor is required for the capture of T. hakonensis in Nagano Prefecture upstream of the MID. The migration of T. hakonensis , which is recognized to be important in such upstream areas, was confirmed in the fishway of the MID (Masumoto et al, 2022).…”

“…All fish caught were released on the upstream side of the fishway, except for those that were to be disposed of in accordance with laws and ordinances. Fish that migrated up the fishway were counted by net cages and assessed on an hourly basis, as shown in Masumoto et al (2022). Caught fish were identified, counted, photographed from the side for identification, and checked for the presence of T. hakonensis nuptial coloration.…”

“…In 1986, all boat channels were converted into stair-type channels. In 1999, a council was established to conduct studies to improve the water environment in the middle reaches of the Shinano River, as reported by Masumoto et al (2022). The council conducted a fish habitat survey and confirmed that approximately 20 species of fish coexisted in the river.…”

“…The top of the bulkhead was changed to a compound tri-arc shape, and the folded section was improved to a semicircle. Additionally, a new rock-ramp-type fishway, known as a "Seseragi fishway," was established to accommodate fish with low swimming power and benthic fish (Masumoto et al, 2022). To contribute to the fish habitat, the slope was designed to be gentle, and hydrostatic areas were provided on both sides of the main stream.…”

“…Only five P. altivelis individuals were caught from 7 PM to 5 AM. In addition, rock-ramp fishways in MID are understood to be used mainly by bottom-dwelling fish, not only for swimming but also as habitat (Masumoto et al, 2022). In the nighttime survey in 2017,…”