Japan's Oyster Industry Crisis: An In-Depth Analysis of the 2025 Autumn-Winter Mass Mortality Even

In the autumn and winter of 2025, Japan's farmed oyster industry faced its most severe production crisis in decades. As the nation's largest oyster-producing region, several bays in Hiroshima Prefecture experienced an abnormal surge in oyster mortality rates. This directly led to a tightening of national supply, rising market prices, and posed a significant challenge to the Japanese government's newly launched oyster export expansion strategy.

Core Data of the Crisis

Crisis Details & Impact

According to statistics from Japan's Ministry of Agriculture, Forestry and Fisheries (MAFF), Japan's total farmed oyster production in 2024 was 149,100 tons. Hiroshima Prefecture, with an output of 94,300 tons, accounted for over 60% of the national total, making it the absolute core supply region for the market.

💰 Price Surge

With the sharp decline in Hiroshima's supply, buyers turned to other regions, pushing up the wholesale price of freshly shucked oysters at Tokyo's Toyosu Market to nearly 6,500 yen per kilogram, an increase of approximately 10% year-on-year.

🍽️ Pressure on Food Service & Retail

Many restaurants in Tokyo specializing in Hiroshima oysters were forced to raise menu prices, with some fried oyster set meals increasing by over 100 yen. Large supermarkets maintained supply by reducing net content or expanding their sourcing channels.

Analysis of Crisis Causes

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Record-Breaking High Temperatures

Summer heatwaves and prolonged high water temperatures exceeded the tolerance limits of oysters.

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Hydrological Anomalies

Reduced rainfall led to increased salinity, and some sea areas experienced insufficient dissolved oxygen.

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Slow Production Recovery

New seed oysters released in November also showed signs of mortality, indicating that production recovery may be slower than expected.

Industry Response & Outlook

In response to the crisis, the Hiroshima Prefectural Fisheries Technology Center has initiated emergency investigations and is exploring mitigation strategies, including adjusting farming depths and schedules. The national government is also reassessing its export targets, with a potential shift in focus towards value-added processed oyster products to stabilize the industry's economic output.

This event underscores the vulnerability of monoculture aquaculture to climate variability and highlights the need for more resilient farming practices and diversified supply chains within Japan's seafood sector.