Japanese aquarium cheers up lonely sunfish with cardboard cutouts of people

How do you perk up a lonely fish? This may sound like the start of a particularly silly joke, but it was a very real challenge faced by staff at a Japanese aquarium when they noticed their sunfish was ailing.

Almost as soon as the Kaikyokan Aquarium in Shimonoseki, southern Japan closed for renovation in December 2024, the sunfish became unwell, the aquarium said in a post on X.

“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.

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

A picture posted by the aquarium shows the sunfish swimming in its tank, one of its eyes turned toward makeshift “people” made from cardboard cutout faces and aquarium uniforms on hangers stuck to the glass. Staff have been waving at the sunfish, too, in an effort to cheer it up.

A lonely sunfish does seem unlikely, the aquarium said, but it added that this fish is curious and would swim up to the front of its tank whenever people came to visit.

But once visitors stopped coming, it stopped eating its jellyfish meals and began to rub its body against the tank, leading staff to suspect that it had developed digestive issues or was infected by parasites, Japanese newspaper Mainichi Shimbun reported.

Ocean sunfish live in the open sea in temperate and tropical regions all over the world, and have washed ashore in places as varied as Australia, California, Portugal, Spain and Oregon. They can grow staggeringly large, weighing up to 1,900 kilograms (more than 3,300 pounds) and measuring up to 3.3 meters (nearly 11 feet) long. This specimen in the aquarium is much smaller, but it shares the lopsided bullet-shaped body and long fins that give the species such a distinctive look.

Another Japanese aquarium came up with a similarly creative solution to keep its animals used to human interaction. During the Covid lockdown in 2020, Tokyo’s Sumida Aquarium asked for volunteers to FaceTime its 300 spotted garden eels, who had become shy without the presence of visitors, making it difficult for staff to check up on them and make sure they were healthy.