We used an electric shocker to control smallmouth bass!

Beginning in late May, it was time for smallmouth bass to spawn again this year. At this time of year, spawning parent fish build mortar-shaped nests in shallow, calm water. Members of the Institute of Freshwater Biology used an electric shocker to capture individuals as they gathered at the spawning sites.

Smallmouth bass are piscivorous fish of the sunfish family, in the order Perciformes, native to North America. Since 2005, the Department of the Environment has listed smallmouth bass as a Specified Alien Species under the Invasive Alien Species Act, and keeping them without a permit is prohibited. In addition, re-release is prohibited by Nagano Prefectural Ordinance. Typhoon Hagibis caused a temporary decline in the smallmouth bass population in the main Chikuma River, but eDNA surveys and other methods indicate that their distribution may be gradually expanding again, making it necessary to conduct impact assessments and take measures based on scientific knowledge.