Marine conditions in the North Pacific have significantly reduced suitable habitat for Japanese chum salmon over the past 25 years, according to new research from Hokkaido University.
Known in Japan simply as “shirozake,” or salmon, chum salmon can be recognised by their faint vertical stripes and silvery sides.
Today, most of the salmon consumed in Japan is imported from countries like Chile and Norway, according to the Ministry of Agriculture, Forestry and Fisheries. But just two decades ago, Japanese chum salmon made up a much larger share of domestic salmon consumption, according to a statement by the university.
Researchers from the Arctic Research Center at the university found that suitable marine habitats for chum salmon have shifted significantly over the past 25 years. By analysing publicly available data and environmental records from 1998 to 2022, the team developed models showing how suitable habitats for Japanese chum salmon have changed.
“The results show that changing ocean conditions have altered where chum salmon can thrive. Suitable habitats have declined overall due to ocean warming, reduced zooplankton which are an important food source, and increasingly frequent marine heatwaves,” according to Assistant Professor Irene D Alabia. “Our results show broad-scale habitat loss in the North Pacific for chum salmon.”
The statement noted that the fish are moving northward, expanding into higher-latitude waters toward the Chukchi Sea as they lose suitable habitats along the southern edge of the North Pacific and the Gulf of Alaska. This “poleward shift” suggests that climate change is reshaping the marine environment on which chum salmon depend. This habitat loss coincides with the recent decline in Japanese chum salmon populations.
Marine ecosystems are particularly sensitive to climate change. Rising ocean temperatures, altered food webs, and extreme heat events are reshaping species distributions worldwide.
“Tracking the redistribution of chum salmon habitat is crucial for conserving the declining salmon resources,” Alabia noted.
Even intensive hatchery programs may not be enough to offset large-scale environmental change. As the North Pacific continues to warm, the future of Japanese chum salmon may depend on how quickly fisheries management and conservation strategies adapt to a rapidly changing ocean.