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

为了阐明日本沙丁鱼种群的年代际变化将如何与全球海洋变暖有关，我们研究了沙丁鱼十年变率的幅度变化以及中世纪气候异常周围的气温和古生产力的变化，作为它们对气候变化反应的类比。从日本别浦湾沿岸海洋沉积物中重建了沙丁鱼的丰度。记录显示，沙丁鱼具有百年尺度的变异性(250-300年)，与西北太平洋的中世纪气候异常/小冰期过渡相对应，沙丁鱼对气候变化没有明确的反应。相反，沙丁鱼丰度的百年变异性与北美重建的PDO指数和东亚异常降雪指数中发现的全流域气候变异性相似。沙丁鱼丰度百年变化的驱动因素之一可能是西北太平洋的猎物丰度。

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.