Ocean temperatures in Japanese waters have surged, hitting record highs over the past three years, with devastating effects on marine ecosystems and the fishing industry. The Japan Meteorological Agency highlighted that this three-year consecutive trend of record-high sea temperatures, which began in 2021, marks the first occurrence of such extensive warming since the agency commenced monitoring sea surface temperatures in 1982. These rising temperatures have had significant impacts, with the average ocean surface temperature near Japan in 2023 being 1 degree Celsius higher than the 30-year average from 1991 to 2020, underscoring the severity of the warming trend.
Anomalies in sea temperatures have been particularly noticeable during different periods of the year, with the ocean surface temperature being notably higher than normal, especially in the June-August, September-November, and December-February periods. Such deviations in sea temperatures have been documented over the years, including the largest difference in the surface ocean temperature during the June-August period in 2022 and previous notable anomalies in 1998 and 1999. Notably, the record-high temperatures have impacted the distribution of marine life, with the Black Current, a warm ocean current flowing near Japan, experiencing shifts in its direction that have led to the migration of various fish species to unexpected regions like the Tohoku area, where fishermen have made remarkable catches of species not typically seen in those waters.
The consequences of the rising sea temperatures are dire for the fisheries and aquaculture sectors, affecting the traditional catches of cold-water fish like salmon while altering the growth patterns of seaweed that thrive in cooler waters. Such shifts in marine life patterns and the warming of ocean waters have raised concerns about the future sustainability of fisheries and the delicate balance of marine ecosystems in Japan. Despite the unpredictability of how these changes will progress, it is evident that immediate action and interventions may be required to safeguard marine biodiversity and the livelihoods of those dependent on the seas for sustenance.