The increase in ocean temperatures in waters near the Japanese archipelago over the past few years has reached record highs, a direct consequence of global warming. The Japan Meteorological Agency noted a significant rise in ocean surface temperatures, with 2023 marking the third consecutive year of record-high temperatures, impacting various marine ecosystems and industries in the region. The agency reported that the average ocean surface temperature from June to August in 2023 was one degree higher than the 30-year average from 1991 to 2020.
The continuous rise in water temperatures has had noticeable effects on marine life and ecosystems in Japan. For instance, coral off the Izu Peninsula of Shizuoka Prefecture has experienced bleaching, a phenomenon often linked to high water temperatures. Additionally, the changing sea temperatures have led to shifts in fish populations, with species not typically found in certain regions being caught due to the altered environment caused by warming waters. This trend is particularly evident in the Tohoku region, where fishermen have reported catches of fish that are uncommon in those waters, such as giant trevally and spangled emperor, which are more commonly found in southern Japan.
The impact of warming sea temperatures is not limited to marine life but also extends to the fisheries and aquaculture industries in Japan. The Fisheries Agency has noted changes in fish populations and catches, with cold-water fish like salmon decreasing in numbers off the Tohoku region while warmer water species like yellowtail and blowfish are being caught in Hokkaido. The higher water temperatures are also affecting the growth of seaweed, a vital component of marine ecosystems, as it typically thrives in colder waters. This shift poses a challenge for industries reliant on a stable marine environment, highlighting the broader implications of rising sea temperatures on various sectors in Japan.