Mechanism driving depleted anchovy and sardine abundance and their amplitude/periodicity changes on decadal timescales during the Medieval Warm Period

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To elucidate how decadal-scale variability of Japanese sardine stock will change in relation to global ocean warming, we examined changes in amplitude of sardine decadal variability and changes in peleotemperature and paleoploductivity around Medieval Climate Anomaly as an analogue for their response to climate change. Sardine abundance was reconstructed from coastal marine sediments of Beppu Bay, Japan. The record showed centennial-scale variability (250-300 years) and no clear response of sardine to climate changes corresponding to Medieval Climate Anomaly/Little Ice Age transitions in the western North Pacific. Rather, centennial variability of sardine abundance showed a similar pattern to basin-wide climate variability found in the reconstructed PDO index in the North America and the abnormal snow index in the East Asia. It is possible that one of driving factors of the centennial variations in sardine abundance is prey abundance in the western North Pacific.