Reasons for the Sardine Shortage

Decline in the resource itself and a sharp drop in recruitment:

• The population of key age groups has plummeted. The estimated number of new fish recruits in 2023 was only 33.2 billion, far below the strong 2022 cohort (94.3 billion).
• Plummeting egg production: Initial egg production for the 2026 cohort stood at only 99 trillion, a drastic drop from the 697 trillion recorded the previous year.
• Deteriorating physical condition of adult fish: The physical condition of adult fish has steadily worsened since 2018, likely leading to reduced reproductive capacity.

Anomalous marine environment and water temperatures off eastern Hokkaido:

• Abnormally low water temperatures in this region prevented the expected formation of summer fishing grounds, meaning fish schools failed to migrate there for feeding as usual.
• "Kuroshio Large Meander" hypothesis: Researchers speculate that a previous "Large Meander" of the Kuroshio Current pushed warm water toward eastern Hokkaido, causing fish schools to extend their northward feeding migration into Russian waters; once the meander ended and water temperatures returned to normal, feeding conditions deteriorated, negatively affecting the fish's physical condition and migration routes.