Skip to Content


April 2020

The Jellyfish that Saved an Aquarium

Moon jellyfish at the Jellyfish Dream Theater

The Kamo Aquarium in Tsuruoka City, Yamagata Prefecture, is home to one of the world’s biggest collections of jellyfish.

The Tsuruoka City Kamo Aquarium is located on the Sea of Japan coast in the south of the Shonai region of Yamagata Prefecture. The previous aquarium, the Yamagata Prefectural Aquarium, opened in 1930 and was a popular local cultural facility, attracting more than 200,000 visitors per annum in the latter half of the 1960s after it moved to the new building and reopened as the Kamo Aquarium. However, with increasing options for leisure, visitors dropped below 100,000 in the latter half of the 1990s, and though the aquarium held exhibitions of the Asian small-clawed otter, sea otter and other popular animals, this didn’t produce the results that were hoped for.

At that time, baby jellyfish suddenly appeared from the polyps of the upside-down jellyfish which were attached to coral reef that was being displayed as a special exhibit. Those jellyfish were then raised and were exhibited when they had grown, and because the sight of the jellyfish softly swimming in the tanks was well received, the aquarium began to put effort into the jellyfish exhibits.

Watanabe Yohei, from the general affairs department at the Kamo Aquarium, says, “What really got the ball rolling was the Kurage wo Taberu Kai (Jellyfish Dinner Party), which was held in 2000 to promote the fact that we had the biggest variety of jellyfish on display in Japan, with fifteen varieties. The unique foods offered, including jellyfish sushi and shabu-shabu were widely talked about, and led to the aquarium being known across the country. "After this event, the aquarium started offering ramen and ice cream with jellyfish bits inside, jellyfish sashimi set meals, and more at the aquarium restaurant. They also became very popular.

Over eighty varieties of jellyfish can be gathered throughout the year along the Shonai Beach which expands out in front of the Kamo Aquarium, and so initially, the exhibits centered around local jellyfish, including moon jellyfish and Japanese sea nettles. However, jellyfish only live for about a year at most, and so stable jellyfish breeding was necessary to regularly exhibit the jellyfish. Watanabe says, “There were many things we didn’t know about jellyfish breeding, and we developed appropriate breeding methods for each species through repeated trial and error. The right size and water flow for each jellyfish species is necessary for the exhibit tanks as well, so we had to improve on that. "

Kamo Aquarium established the Tsuruoka Jellyfish Laboratory in 2003, producing many results including succeeding in breeding a wide variety of jellyfish, such as edible jellyfish, brown-banded moon jellyfish, and purple jellyfish. Researchers from aquariums and research organizations from all over the world, including the Aquarium de Paris in France, come to learn about this jellyfish breeding and raising.

In 2014, a new aquarium building was built on neighboring land, with more than twice the space for the jellyfish exhibit of the older building, allowing more than sixty varieties of jellyfish to be regularly exhibited. The highlight of the new building is the Jellyfish Dream Theater, where approximately 10,000 moon jellyfishes undulate in a circular tank 5 meters in diameter, one of the world’s largest. In winter, the Theater is illuminated with rainbow-colored lights, producing a fantastical atmosphere.

The aquarium also hosts other events to increase the number of jellyfish fans, such as an overnight event where guests spend the night in front of the aquarium tanks, concerts in the Jellyfish Dream Theater, and more. The aquarium has now become one of the representative tourist spots for Yamagata Prefecture, attracting approximately 500,000 visitors annually from Japan and abroad.

A concert at the Jellyfish Dream Theater

Watanabe says, “We procure new jellyfish and have been given gifts from other aquariums. The species on exhibit differ based on breeding status and season, and we also update the tanks each year, so you can always encounter new jellyfish here. "

Watching the jellyfish move peacefully through the water has a soothing effect that will calm your heart.