Record-high sea temperatures hit Japanese waters, disrupt fisheries

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

According to reports from Japanese media, this year saw a record-high average temperature of the waters surrounding the Japanese archipelago.

"Asahi Shimbun" journalists analyzed 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 was 0.3°C higher than the previous record 1998 and 1.1°C higher than the average from 1991 to 2020, which is considered "normal."

"Asahi Shimbun" emphasizes that 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.

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

One of the causes 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" reminds us that in the fall 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.