Ocean Warming Shrinks Suitable Habitat for Japanese Chum Salmon

Marine habitats suitable for Japanese chum salmon have declined significantly over the past 25 years due to ocean warming, reduced zooplankton availability and increasingly frequent marine heatwaves, according to new research from the Arctic Research Center at Hokkaido University. The fish are shifting northward toward the Chukchi Sea as habitats along the southern edge of the North Pacific and the Gulf of Alaska deteriorate.

Researchers at Hokkaido University analysed publicly available data and environmental records from 1998 to 2022, developing habitat suitability models showing how suitable zones for Japanese chum salmon have changed across the North Pacific over a quarter century. The study found broad-scale habitat loss driven by rising sea surface temperatures, altered food webs and extreme heat events. Chum salmon, known in Japan as shirozake, are moving into higher-latitude waters as southern habitats become unsuitable. Most salmon consumed in Japan is now imported from Chile and Norway.

The habitat loss coincides with a documented decline in Japanese chum salmon populations, a species that once made up a much larger share of domestic salmon consumption in Japan. Marine ecosystems are particularly sensitive to climate change — rising temperatures, shifted food webs and intense heatwaves are restructuring species distributions worldwide. Researchers from the university note that even intensive hatchery programmes may be insufficient to offset large-scale environmental change if ocean conditions continue to deteriorate.

Assistant Professor Irene D Alabia stressed that tracking the redistribution of chum salmon habitat is crucial for conserving declining salmon resources. The research suggests that fisheries management and conservation strategies must adapt rapidly to a changing North Pacific. The northward range shift observed in the study also raises concerns about how species interactions and food security across Arctic coastal communities will evolve as climate change continues to reshape the marine environment. The findings point to the need for dynamic, climate-informed management approaches rather than static conservation boundaries.

Key figure — 25 years of habitat data analysed (1998 to 2022) showing broad-scale habitat loss across the North Pacific