The Ministry of Agriculture, Forestry and Fisheries of Japan and the Hiroshima Prefectural Government have reported that since the start of the harvest season in October, 80% to 90% of the cultivated oysters harvested in Higashihiroshima City and Kure City in Hiroshima Prefecture have died before being harvested.
On the 19th, Japanese Minister of Agriculture, Forestry and Fisheries, Kensuke Suzuki, inspected an oyster farm in Higashihiroshima City to investigate the losses. He later told reporters that the government will determine the cause and coordinate with local authorities to provide support to oyster farmers.
Suzuki mentioned earlier that some areas in neighboring Okayama Prefecture and eastern Hyogo Prefecture also reported oyster deaths. These three prefectures all face the Seto Inland Sea.
Japan's oyster farming industry is well-developed, with major farming areas along the Seto Inland Sea in Hiroshima Prefecture, Okayama Prefecture, and Hyogo Prefecture. Based on data extrapolated from the 2023 statistical survey of the Ministry of Agriculture, Forestry and Fisheries in Hiroshima Prefecture, Hiroshima Prefecture leads in oyster production with 16,129 tons per year, followed by Okayama Prefecture with 2,568 tons and Hyogo Prefecture with 2,102 tons, with the three prefectures accounting for 81% of the national production.
In Hiroshima Prefecture, oysters farmed for three years show a mortality rate of 60% to 90%. The mortality rate in Ao, Kure City, and Akitsu-cho, Higashihiroshima City, is over 90%, nearly a complete loss. The same is true for Okayama Prefecture and Hyogo Prefecture, where the mortality rate, which was 20% to 50% in previous years, has surged to over 80% this year.
Matsumoto Shigemasa, who has decades of experience in oyster farming, said that 80% to 90% of the oysters he farms will die this year. He has been involved in oyster farming for about 50 years, but this is the first time he has encountered such a large-scale death event.
The exact cause of the mass oyster deaths has not been fully determined, with pathogens and pollution being unlikely, and climate change considered the most significant factor. According to analysis by the Hiroshima Fisheries and Marine Technology Center and experts, the main reasons are "high water temperature" and "high salinity" in the seawater.
Currently, the capture volume of cultivated oysters in Japan has sharply decreased to 20% to 30% of previous years, and prices have risen significantly. Although there is no current estimate of the loss amount, it is estimated to be in the hundreds of millions of yen.