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 des-tination 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 ve-locities 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.