The Kuroshio Current's Impact on Japan's Waters and Fisheries
The first half of 2023 witnessed record-breaking sea surface temperatures around the Japanese archipelago, exceeding even the highs of 1982. This phenomenon, attributed to an abnormal flow of the Kuroshio Current, has significantly impacted marine life and fishing activities.
The Kuroshio Current, a warm current originating in the south, typically turns eastward off the coast of Choshi. However, since late 2020, it has been flowing northward along Honshu, likely due to changes in wind patterns associated with global warming.
This northward shift has brought warmer waters to Hokkaido's Pacific coast, leading to earlier fishing seasons for salmon and trout. However, it has also disrupted traditional fishing grounds, making it difficult to catch salmon and trout towards the end of the season.
The northward movement of the Kuroshio Current also prevents the southward flow of the cold Oyashio Current, creating conditions conducive to "ocean heat waves" – prolonged periods of high sea surface temperatures. These heat waves have been linked to the worst red tide ever recorded on Hokkaido's eastern coast in 2021, caused by an explosion of toxic phytoplankton.
Experts warn that ocean heat waves are becoming increasingly frequent around Japan, posing a significant threat to marine ecosystems and fisheries. The likelihood of these events has quadrupled compared to the early 1990s, highlighting the urgency of addressing climate change and its impact on oceanographic patterns.