Fishermen in Tohoku and Oita are reporting a surge in bonito and oversized rock oysters this summer [1, 2].
This recovery follows a period of record-low catches for bonito in the Tohoku region, signaling a potential shift in marine productivity and food supply stability for coastal communities.
In Oita Prefecture's Saiki City, rock oysters have reached exceptional sizes due to the unique geography of the area. Issei Nagasaki, a lecturer at Tokyo University of Marine Science and Technology, said that rias coastlines allow nutrients flowing from the land to accumulate easily. He said that organisms living in these environments grow with high nutrient levels, making them more likely to become larger and fleshier [1].
Masame Hashimoto of Maruni Suisan noted the superior quality of the current harvest. Hashimoto said the oysters feel heavy when held and that the sea possesses great strength. While some specimens are already large, Hashimoto said some individuals exceed one kilogram [1].
The abundance extends to bonito, which had previously suffered from poor harvests in Tohoku [1]. This trend is mirrored in other regions; for instance, bonito catches in Nakatosa Town, Kochi Prefecture, have more than doubled compared to the previous year [2].
Experts attribute these changes to the end of the Kuroshio Current's large meander and a subsequent rise in seawater temperatures [2]. These oceanographic shifts, combined with the nutrient-rich conditions of the rias coast, have created an ideal environment for these species to thrive [1, 2].
“"1 kiloを超えるものもある"”
The return of abundant harvests suggests that the stabilization of the Kuroshio Current is having a direct positive impact on Japan's migratory fish patterns and shellfish growth. By combining favorable current movements with the natural nutrient traps of rias coastlines, the region is seeing a temporary reversal of the productivity declines that plagued previous seasons.
