In japan’s Seto Inland Sea, oyster beds that supply most of the country are collapsing as mass die-offs devastate harvests. The crisis is concentrated in Hiroshima prefecture, where mortality has reached as high as 90% in parts of the region and the national government has stepped in to support fisheries. This dispatch was filed at 03: 00 PM ET.
Escalating losses and the scale of the problem
Fisheries ministry figures put mortality in affected areas as far higher than a typical season, with localized death rates reaching up to 90%. Hiroshima—which produced 89, 000 tons of farmed oysters in 2023 and supplies almost two-thirds of the country’s farmed oysters—has been hit hardest. Fisheries around the Seto Inland Sea together produce roughly 80% of japan’s oysters, and fishers from west to east, from Hiroshima to Hyogo, report widespread mortalities and poor-quality survivors.
Voices from the water and the festival
“The local oysters were fine until this year, ” said Nobuyuki Miyaoka, a Kure oyster festival attendee, describing shells that are noticeably smaller than in past seasons. At the same festival, long lines formed at oyster stalls even as vendors struggled to find product to serve.
Taketoshi Niina, who runs a small fishery in Kure, called this season’s harvest a “disaster. ” Niina described pulling up lines where about 80% of oysters were dead and said many survivors were too poor in condition to sell to shops and restaurants: “This is something out of the ordinary. And a lot of those that do survive are in poor condition … they are not of a high enough quality to sell to shops and restaurants. This is beginning to hit us financially. The season isn’t over yet, and next year is also looking bad. We’re all exhausted. If this happens again next year then it’s going to threaten businesses. ”
“I’ve never experienced this in my whole career, ” said Tatsuya Morio, an oyster farmer in Hiroshima with more than 20 years’ experience, summing up what many in the industry describe as unprecedented losses.
Drivers, government action and what comes next
Experts and industry actors point to warming seas and a brutal heatwave last year that left oysters deprived of oxygen and food; the season’s mortalities followed an unusually hot summer when average temperatures were notably higher than historical averages. Japan’s government has stepped in with support measures for struggling fisheries as the immediate economic impacts ripple through coastal communities.
Immediate recovery will depend on whether conditions that drove this die-off—higher sea temperatures and the aftermath of last year’s heatwave—abate before the next growth cycle. Fishers say the season remains ongoing and anxiety is high over the coming year; if similar conditions repeat, businesses that depend on oyster farming face sustained financial threat. Watch for further announcements from the fisheries ministry and local prefectural authorities on aid and monitoring plans as harvests evolve in the weeks ahead.
Filed updates will follow as fisheries ministry monitoring continues and fishers in Hiroshima and across the Seto Inland Sea assess the outlook for next season; this account will be updated with official measures and on-the-ground developments when available. Japan’s oyster industry is at a crossroads, and the next months will determine whether this mass die-off is an isolated shock or the start of a recurrent crisis.
