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[Hidden Wonders of Japan] 20,000 Sardines Form a Beautiful Underwater Kaleidoscope in Aqua World Oarai

Sardines take center stage in an Ibaraki aquarium, captivating visitors with dynamic schooling movements that have helped them traverse the harsh natural world.



A school of sardines in Aqua World Oarai's biggest aquarium (provided by Aqua World Ibaraki Prefecture Oarai Aquarium).

Sardines are often seen as vulnerable, easy prey for other fish. That's what I used to think as a child. Indeed, sardines belong to the prey category, but they are not passive, helpless victims. 

And even as prey, they have a vital yet often uncelebrated role in supporting the marine ecosystem by serving as food for other fish.

Sardines protect themselves by forming schools of tens of thousands. By moving in large groups, they can swiftly detect and escape potential threats. This makes it difficult for predators to single them out.

Through these adaptations, sardines have endured the challenges of the unforgiving natural world. At the same time, they are essential contributors to the thriving marine life in our oceans.

(Provided by Aqua World Ibaraki Prefecture Oarai Aquarium)

The Japanese Sardine

Among sardine species, the Ma-iwashi (Japanese sardine) boasts the highest catch in Japan. It has been part of the fishing scene in Ibaraki Prefecture since the Edo Period

It is this famous local sardine species that is now exhibited in our "Great Sea Tank of Encounters," the largest aquarium in Aqua World Oarai.

Previously, we exhibited these sardines simply in their school formations, but we realized that this didn't fully capture the remarkable qualities of the fish. To give sardines a better spotlight, we launched a new program as part of our 20th-anniversary celebration.

The program uses light and sound to highlight the dynamism and vitality of sardine life. It encourages visitors to consider the sardines' resilience as they navigate the intricate web of the food chain. Hence, we named this initiative IWASHI LIFE (sardine life).


However, putting the program together proved quite a challenge. At that time, our lighting system could only turn on and off, so we couldn't create the desired light spectrum. The beautiful schooling movements of the sardines were obscured by the darkness. Even when the light managed to reach the bottom of the tank, the sardines would invariably gather on the opposite side of the light.

The revamped IWASHI LIFE project (provided by Aqua World Ibaraki Prefecture Oarai Aquarium)

After numerous adjustments, we were thrilled to launch IWASHI LIFE in June 2021. This spring, we decided to revamp the program so that visitors could truly appreciate the incredible nature of these creatures. 

Underwater Kaleidoscope

The upgrade involved making changes to the lighting, adding sound equipment, and increasing the sardine population from around 15,000 to 20,000. All these improvements aimed to enhance the portrayal of their captivating schooling behavior. IWASHI LIFE version two made its stellar debut in May.

"Great Sea Tank of Encounters" is an enchanting world where a diverse range of creatures thrive together. By adjusting the placement, depth, and timing of the feedings, we've made it possible for the sardines to move in swirling formations throughout the entire aquarium. The school of sardines, never repeating the same movement, creates a mesmerizing underwater kaleidoscope. 

About Aqua World Ibaraki Prefecture Oarai Aquarium

  • Address: 8252-3 Isohama-cho, Oarai-cho, Higashiibaraki-gun, Ibaraki Prefecture 
  • Opening hours: 9:00 am to 5:00 pm
  • Admission fees: Adults: ¥2,300 JPY ($16 USD), Elementary and Middle School Students: ¥1,100 JPY ($8 USD), Children aged 3 and above: ¥400 JPY ($3 USD)
  • Phone: 029-267-515


(Read the article in Japanese.)

Author: Aqua World Ibaraki Prefecture Oarai Aquarium, contributed to The Sankei Shimbun