Overview
- A six-member expert panel issued a provisional report on Tuesday saying the 2025 die-off in parts of Hiroshima’s Seto Inland Sea was likely caused by a mix of prolonged high water temperatures, high salinity, low rainfall and oyster physiological state.
- The panel recommended immediate operational steps that producers can use, including moving rafts and changing the hanging depth of oysters when risks rise.
- Hiroshima plans to widen monitoring at about 15 sites by adding sensors that track salinity and by installing cages with oysters so farmers can report flesh condition directly to the prefecture.
- Officials will publish risk-tiered prefectural alerts tied to the new monitoring data so producers can make timely decisions, though the panel stressed its conclusions are provisional because rainfall and conditions vary between the prefecture’s east and west.
- Hiroshima is Japan’s largest oyster producer, and the panel linked last year’s record low rainy season and a long run of days above 20°C to a higher risk state in oysters that likely made the die-off more severe.