Video introduction of herring spawning "Gunrai" in Rumoi County, Hokkaido

This video, titled "The Sea Turned White?! Drone Footage of a Pacific Herring Swarm!" (海が白くなる!? ニシン群来のドローン撮影に成功！), was uploaded by "Hidemi Imai" (今井秀美).

In Obira, Hokkaido, the blue sea is dyed white as if milk has been spilled in it. This phenomenon is caused by herring swarms, which occurs when herring (in this case pacific herring), a fish heralding the arrival of spring in Hokkaido, spawn and fertilize eggs.

A video shot from the sky captures the phenomenon that looks like a white sash on the blue sea. Large schools of pacific herring come to Obira to spawn, and you can see the beauty of life as they flop about the surface of the water. Check out the video to see the pacific herring swarm up close!

What Kind of Place is Obira?

Obira is a small town in western Hokkaido with a population of just a few thousand. It's located a few hours north of Sapporo via train, making it a bit of an out-of-the-way destination, but it's home to many tourist attractions. There are golf courses and surf spots, as well as facilities for learning about the local culture. In addition, there are ski resorts that can be enjoyed during the winter months, and campsites that can be visited during the summer. Obira is a nice destination to check out if you're looking for things to do in Hokkaido that are a bit more off the beaten path.

Information about the Pacific Herring and the Causes and Conditions for Swarms in Hokkaido, Japan

Photo：Pacific herring spawning

The pacific herring (scientific name: clupea pallasii) is a silvery-white fish found mostly in the Pacific Ocean. Pacific herring are generally 30-35 cm (12-13 inches) long but can grow as large as 45 cm (~17.5 inches).
Pacific herring feed on phytoplankton and zooplankton, and their natural predators are salmon, whales, seabirds, etc.

Every year from February to March, the coast of the Sea of Japan in Hokkaido turns a milky white color.

The pacific herring come to the coast in large numbers during spring, so much so, that they are said to herald the arrival of spring in Hokkaido. In the world of haiku, a type of Japanese poetry, the word "Nishin Kuki" (鰊群来, herring coming in large schools) is a seasonal word to symbolize spring.

Herring swarms occur when herring come to the coast to spawn and fertilize eggs. The white colors are a phenomenon that occurs when males simultaneously fertilize eggs that have been laid on seaweed.

In 1954, after being observed along the coast from Yoichi to Oshoro, a 20km stretch on the peninsula northwest of Sapporo, the pacific herring swarms were not observed again for many years.
It wasn't until 1999 that the pacific herring swarms were observed in the area, for the first time in 45 years.

In order for the herring swarms to occur, two conditions must be met: the sea must be calm during the herring spawning season, and the water temperature must be relatively high, around 5 degrees Celsius. In addition, the herring swarms seem more likely to occur on cloudy days from February to April.

When and Where to See the Pacific Herring Swarms

Source :YouTube screenshot

The herring swarms are a phenomenon seen during the spawning season, which, for the pacific herring in Japan, is from late January to early May, and February to March is said to be the most active season.

In addition, since spawning often takes place at night, the ocean can be seen turning milky white around dawn, disappearing around noon. This means that you have a higher chance of seeing the phenomenon during the morning.

The places where herring swarms can be seen are the coasts of Hokkaido along the Sea of Japan and within Ishikari Bay. In Otaru, herring is synonymous with spring.

If you want to see the herring swarms, we recommend visiting the Otaru coast from February to March! However, because it's a natural phenomenon, it's not always possible to see the pacific herring swarms, even if you visit at the right time and place. That being said, it's still worth a try to see the incredible sight.

Delicious, Seasonal Pacific Herring Recipes!

Photo：Nishin soba

In Hokkaido, which is famous for herring production, there are various ways to eat delicious seasonal herring. Pacific herring are considered to be in season only in spring, but it's said that they are also in season in autumn.

In Japan, pacific herring are processed in many different ways. Some of these are herring roe, kombu-maki (kelp rolls), nuka nishin (herring in rice-bran paste), and migaki nishin (dried and sliced herring). One of the rarest products is frozen herring stuffed with mentaiko (spicy cod roe). Migaki nishin is famous for its use in nishin soba (a bowl of soba topped with a dried herring), a specialty of Kyoto.

In addition, we also recommend carpaccio, which is made by cutting the fish into three pieces and pouring a seasoning mixture of lemon juice, olive oil, salt, and pepper over the meat. The herring and pumpkin pie from Ghibli's "Kiki's Delivery Service" is another dish that tastes even better when made with pacific herring caught during season in Hokkaido. If you like cooking, we recommend trying a simple recipe, which requires just some cooked herring, vegetable paste, white sauce, and cheese inside a pie topping, and then baking.

Seaweed With Roe From the Pacific Herring

Photo：Komochi kombu

When herring come to the shallows to spawn in large schools, they lay their eggs on seaweed. Because the eggs are sticky, they tend to adhere to seaweed, such as kombu (edible kelp) and wakame seaweed.

Originally, natural seaweeds on which the eggs were laid naturally were harvested, but due to a decrease in catches, there are fewer and fewer of them. Therefore, seaweed is now hung where the pacific herring will pass by to encourage spawning.

The result of pickling these seaweeds in salt creates 2 delicious types of seaweed called komochi kombu and komochi wakame. They are often used in festive New Year's dishes in Japan to bring good luck.

Summary of Herring Swarms and Spawning in Hokkaido

The pacific herring swarms resemble a milky white sash fluttering in the blue sea. The contrast between the blue and white colors allows for some vivid photography as well.

It's fascinating to think that this phenomenon occurs when large schools of herring gather to spawn and release their sperm in order to procreate.

If you're traveling to Hokkaido in February and March during spring, consider visiting the coast of Otaru. If you're lucky, you may be able to see the herring swarms, a mysterious phenomenon of life.