Rising summer temperatures undermine threatened charr populations in the Shiretoko Peninsula

A 2°C rise in mean summer temperatures or a 20% increase in time spent above 16°C could lead to population declines exceeding 40% in the threatened Southern Asian Dolly Varden (SADV) charr, according to research conducted in the Shiretoko Peninsula, a UNESCO World Natural Heritage site. The study integrated fish density, biomass, and environmental DNA (eDNA) concentration across multiple streams with water temperature records, revealing significant thermal stress impacts on SADV populations. Streams with artificial barriers exhibited higher summer temperatures and prolonged exposure to critical thresholds, further exacerbating population vulnerability. These findings underscore the urgent need for thermal vulnerability assessment in river management and conservation planning under future climate scenarios.

Araki, H., Urabe, H., Inoue, S., & Ogiwara, H. (2026). Rising summer temperatures undermine threatened charr populations in the Shiretoko Peninsula. Climate Change Ecology, 12, 100116. https://doi.org/10.1016/j.ecochg.2026.100116