Japan survey maps distributions for 113 of 115 freshwater fish species

Japan’s Environment Ministry published results on freshwater fish from a nationwide baseline nature survey covering 2022–2025 on 5 October. The survey compiled distribution information for 113 of its 115 target species and also organized records for 11 related species outside the target group.

The findings indicate northward range shifts for some brackish-water and migratory fish and spread of some Japanese native species into other river systems through human introduction. Researchers also confirmed an invasive fish for the first time in a Honshu river during fieldwork in the Tone River basin in Gunma in 2024; the ministry said environmental DNA samples there had detected traces in 2023 and 2024.