Some of the Sea of Okhotsk's islands are quite large, including Japan's second largest island, Hokkaido, as well as Russia's largest island, Sakhalin

Bluefintuna in the Sea of ​​Okhotsk and yellowtail off the coast of Otaru

JAPAN
Saturday, September 19, 2020, 23:00 (GMT + 9)

The news that the bluefin tuna is caught in the Sea of ​​Okhotsk, the northernmost sea in Japan, has become a hot topic. Furthermore, the warm sea fish yellowtail seems to be migrating in the sea of ​​Hokkaido. What is the cause?

Bluefin tuna are doing well in the North Sea

"Furubiracho", the Shiribeshi General Promotion Bureau, is about 1 hour and 20 minutes by car from Sapporo, the center of Hokkaido. Located at the base of the Shakotan Peninsula that juts out into the Sea of ​​Japan, it is also right next to Otaru, which is famous as a tourist city.

Small Pacific bluefin tuna (Photo: courtesy Sankei)

Now, in the Sea of ​​Japan off the coast of Furubira Town, fishing boats aiming for bluefin tuna are leaving every day. Bluefin tuna have the image of migrating widely in the southern sea, but they have been fishing constantly off the coast of Kodaira for two years, and sometimes even those weighing nearly 50 kg are mixed. It is said that many people keep the keep size while there is a rule that weighs less than 30 kg.

Not only that, but also in the Sea of ​​Okhotsk further north, small tuna of about 10 kg are migrating, and it is said that they have been witnessed chasing food in groups.

Yellowtail amberjack, Seriola lalandi (Photo: courtesy AC)

Why are tuna in the North Sea?

In Hokkaido, the temperature rose significantly from around the Obon festival in August, and there were days when it recorded one of the hottest temperatures in Japan and was featured in the news. As a result, it is said that the sea surface temperature is becoming extremely high in the waters around Hokkaido.

In the case of bluefin tuna, it is said that they migrate when the sea surface temperature is 16 to 22 degrees Celsius, but this year's seawater temperature around Hokkaido applies to almost the entire area.

Mahi-mahi or common dolphinfish, Coryphaena hippurus (Photo: courtesy AC)

As a result, not only are the bluefin tuna themselves suitable for migration, but also many small yellowtails that serve as food are migrating. On the other hand, there is concern that the original seafood will decrease. 

In recent years, squid, which is the main catch of Hokkaido, has been unfished, and some have pointed out that this is also partly due to the rise in seawater temperature.

Various steps have been taken to prevent the progress of climate change, but even so, such changes cannot be stopped overnight. It may be necessary to calmly grasp the current situation, respond to changes in catches, and review fishing grounds and fishing methods.

Author: Tetsuro Wakimoto / Fish Research Institute | TsuriNews

editorial@seafood.media
www.seafood.media

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