Massive Oyster Die-Off in Hiroshima Raises Alarms, Declared Disaster Level

Unprecedented mortality rates among oysters along the Hiroshima coast have left local producers stunned and prompted government intervention.

An unusual and widespread phenomenon of oyster mortality has been reported along the coastal areas of Hiroshima Prefecture. Local aquaculture operators have discovered that recently harvested oysters are found with their shells gaping open and devoid of meat. This unsettling sight has been described by producers as deeply disturbing, with many stating they have never witnessed such an event in decades of operation.

Hiroshima Prefecture is the leading producer of farmed oysters in Japan. According to prefectural authorities, numerous aquaculture businesses have reported significant oyster deaths, with the most severe impacts observed in fishing grounds near the Ondo Bridge in Kure City and on the eastern side of Kurahashi Island. Reports indicate a drastic reduction in harvestable oysters; one producer mentioned that 100 oyster lines, which typically yield over 200 kilograms of shucked oysters, produced only about 30 kilograms in a recent harvest. Furthermore, many of the surviving oysters have turned brown, rendering them unsaleable.

The Hiroshima Prefectural Fisheries and Aquaculture Technology Center suggests that the extreme heat during the summer months led to elevated seawater temperatures. Coupled with a lack of rainfall, this resulted in increased salinity, ultimately causing physiological distress in the oysters.

In response to the escalating situation, the Japanese Minister of Agriculture, Forestry and Fisheries visited an aquaculture site in Higashi-Hiroshima City. At the affected farms, reports indicate that approximately 90% of the oysters have died. The Governor of Hiroshima Prefecture, Yuzaki, has characterized the current situation as reaching a "disaster level" and expressed that the national government recognizes the crisis. He emphasized the importance of preserving the brand value of oysters, which are strongly associated with Hiroshima.

Beyond Hiroshima Prefecture, data compiled by the Fisheries Agency reveals that other prefectures with oyster farms in the Seto Inland Sea, including Ehime, Kagawa, and Hyogo, have also experienced higher-than-average oyster mortality rates. These regions attribute the losses to factors such as high seawater temperatures, insufficient feed, and low dissolved oxygen levels in the water.