Japanese aquarium places cardboard cutouts of people near sunfish tank to cure its loneliness

An aquarium in Japan is using cardboard cutouts of visitors to cheer up its lonely resident sunfish who stopped eating after the building closed to real-life visitors.

Kaikyokan Aquarium in Shimonoseki, southern Japan has been closed to the public for renovations since December 2024. Its sunfish fell ill soon after and staffers struggled to understand why the creature suddenly stopped eating, the aquarium said on X.

Aquarium staff in Japan used cardboard cutouts of visitors to help cheer up the depressed sunfish. X / @shimonoseki_aq

Sunfish, while typically preferring to live in solitary, are naturally curious and tend to approach divers in the wild. X / @shimonoseki_aq

In the wild, sunfish largely prefer to live alone or occasionally link up in pairs. Likewise, the Kaikyokan Aquarium’s listless fish has long been the sole occupant of its tank.

But what sets sunfish apart from many other solitary creatures is that they are often stimulated by their curiosity. They are harmless to people and are known to fearlessly approach divers in the wild, according to National Geographic.

Without its usual crowd of spectators, Kaikyokan’s sunfish essentially started to fall into a deep-sea depression.

“We couldn’t figure out the cause and took various measures, but one of the staff members said, ‘Maybe it’s lonely because it misses the visitors?’ We thought 99% chance ‘No way!’ But we attached the uniforms of the staff members (to the tank) with a little bit of hope,” the aquarium said.

Keep up with today’s most important news

Stay up on the very latest with Evening Update.

Thanks for signing up!

“Then…the next day, it was in good health again!”

A photo posted by the aquarium shows the cutouts facing the tank with the uniforms pasted on the glass.

While it’s nearly impossible to tell what creatures like fish are feeling, the sunfish’s eye continuously tracked the cardboard cutouts while it swam by. Staff have also been waving at the sunfish whenever they pass the tank.

The Kaikyokan Aquarium has been closed for renovations since the beginning of December 2024. Google Maps

The sunfish had gone on a hunger strike once the aquarium closed. Before, it would often swim up to the glass to observe visitors, but when the renovations started, it stopped eating its jellyfish meals and would drag itself along the walls of the tank.

Staff originally thought that it must’ve been plagued with digestive issues or even a parasitic infection, the Japanese newspaper Mainichi Shimbun reported. Turns out, it just couldn’t cope with the unexpected isolation.

The sunfish has since bounced back with renewed vigor thanks to the staff’s creative solution.

Ocean sunfish in the open sea can grow staggeringly large and have frequently been mistaken for monsters or alien fish when washing ashore.

They can weigh more than 3,300 pounds and measure up to nearly 11 feet long. Ones in captivity, like the lonely sunfish, are typically smaller.