About 500 fans attend the 16th birthday party of sea otter Riro on March 30 at Marine World Uminonakamichi in Fukuoka. (Yusuke Ogawa)

FUKUOKA--Only three sea otters remain at aquariums in Japan, and they are now treated like rock stars because of their advancing years.

Japan was once home to dozens of the cute mammals. But the species became endangered in the wild, and trade in sea otters fell under strict regulations.

Japanese aquariums tried to breed otters in captivity but with limited success.

The three sea otters left in Japan are too old to breed. And with expectations that they, too, could soon disappear, crowds of visitors are traveling from around the country to take what could be their last look at the otters.


According to the Tokyo-based Japanese Association of Zoos and Aquariums, Izu Mito Sea Paradise in Shizuoka Prefecture became the first in the nation to start breeding sea otters in 1982.

Sunshine Aquarium was the first in Tokyo to do so, in 1984.

During the economic boom from the 1980s to 1990s, large aquariums sprang up in redeveloped coastal areas across the country: Suma Aqualife Park Kobe in 1987; Osaka Aquarium Kaiyukan in 1990; and Yokohama Hakkeijima Sea Paradise in 1993.

Along with dolphin shows, sea otters were a big draw at the aquariums. At the peak in 1994, more than 120 sea otters were living in aquariums in Japan.

However, overhunting for fur depleted the global population of sea otters, and international trade was strictly regulated under the Washington Convention.

Sea otter imports to Japan from the United States ceased in 1998, and from Russia in 2003.

In 2000, the International Union for Conservation of Nature listed the sea otter as endangered. That year, 88 sea otters were housed in aquariums in Japan.

But the number plummeted to 30 in 2011 and to 10 in 2017.

The last sea otter in the Tokyo metropolitan area died at the Aqua World Ibaraki Prefecture Oarai Aquarium in 2018.

Although some sea otters were born in captivity in Japan, most of them did not live very long.

At Marine World Uminonakamichi in Fukuoka, nine pups were born, but six died within a few weeks to a year.

Continuous breeding is difficult, and the fertility rate of captive sea otters declines with each generation, experts said.

The remaining three otters are: 15-year-old Kira and 18-year-old May, both female, in Toba Aquarium in Mie Prefecture; and 16-year-old male Riro in Marine World in Fukuoka.

One sea otter lived for 28 years at an aquarium in the United States.

However, the lifespan of wild sea otters is estimated to be around 10-15 years for males and 15-20 years for females.

The three remaining sea otters in Japan are approaching “elderly” age, and breeding is extremely difficult.


Word of their plight spread over social media during the COVID-19 pandemic.

In spring last year, when Toba Aquarium released a photo book featuring May and Kira, 500 copies were sold out in about a minute.

Additional copies were printed, and 7,000 were scooped up in about six months.

To avoid overcrowding, the aquarium since the end of 2022 has prevented visitors from stopping and watching the sea otters in front of their tank during mealtimes on weekends and holidays.

During the pandemic, videos of the sea otters posted by the aquarium on Twitter have received an overwhelming number of views compared with clips featuring other animals.

One video of May holding a celebratory flag when Japan won the World Baseball Classic championship in March received around 1 million views and 22,000 likes.

The aquarium’s Twitter account had 72,000 followers in January 2020 before the pandemic, but the number nearly tripled to 225,000 as of March 2023.

“During the stay-at-home period, people found the sea otters to be cute through photos and videos on social media, which led to a surge in their popularity,” said Mayu Sakakibara, a public relations official at the aquarium.

“In addition, more media outlets have covered our sea otters, coinciding with the decrease in the population (in the country),” she said.

Marine World said it receives many inquiries from distant locations, such as Tokyo and Osaka, particularly from parents who want their children to see Riro while he is still alive.

On March 30, when Riro turned 16, about 500 people visited Marine World, and 300 commemorative postcards with his photo were sold out quickly.

Visitors lined up before the aquarium opened. Some were carrying travel suitcases.

“Today is most visitors I have ever seen,” said Kana Fujimori, 27, an aquarium caretaker.

One woman in her 30s who came from Takamatsu said she stayed overnight in Fukuoka.

She lined up about an hour before the opening.

“I came here because I wanted to breathe the same air as Riro,” she said.

She became a fan of sea otters after watching videos of the creatures during the COVID-19 stay-at-home period. She now visits Toba Aquarium as well.

“I want to support the remaining sea otters until the very end,” she said.

Flower bouquets and letters containing messages such as “Live healthy” were delivered to Marine World from all over the country.

Some visitors were even moved to tears at Riro’s birthday celebration.

“I never imagined that the number of sea otters would decrease this much during my lifetime,” said Miki Akiyoshi, 35, an aquarium caretaker. “I want to pay close attention to Riro’s health so that he can spend his days in good health.”