Record-high sea temperatures grip Japanese waters, impact the fishing industry

According to the newspaper Asahi Shimbun, the average surface temperature of the waters around the Japanese archipelago in the first half of this year was 18°C. This is the highest value since 1982 when data collection on this topic began.

According to information provided by Japanese media, the average temperature of the waters surrounding the Japanese archipelago was recorded as record-high this year.

"Asahi Shimbun" journalists analysed data provided by the Japan Meteorological Agency concerning the average surface temperatures of the waters. The data were collected based on readings from 10 marine areas taken every ten days for the past 43 years.

The analysis shows that the average temperature of these areas from January to June this year was 18°C. This means it was 0.3°C higher than the previous record from 1998 and 1.1°C higher than the average for the period from 1991 to 2020, which is considered "normal."

"Asahi Shimbun" emphasises that particularly the water temperature in the area stretching east of Hokkaido island, which lies in the north of the archipelago, was 2.4°C higher than usual in the first half of the year.

Toru Miyama, a marine physicist from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), believes this results from the change in direction and northward extension of the Kuroshio (known as the Japan Current), which brings warmer waters from the south. The scientist adds that this phenomenon is also related to global warming.

This change has already impacted fishing, among other things, forcing the fishing season to start a week later compared to the previous year.

Kazuhiko Nakajima, director of a fishermen's association based in Sapporo, told the newspaper that in recent years, salmon and trout fishing has become practically impossible at the end of the season due to rising sea temperatures.

One cause of these anomalies in fishing grounds is "marine heatwaves," a statistically rare phenomenon in which high sea temperatures persist for more than five days.

"Asahi Shimbun" points out that in the autumn of 2021, the eastern coast of Hokkaido was hit by the worst "red tide" ever recorded, causing the death of vast numbers of sea urchins, salmon, and octopuses.