Sea otters, one of the most popular attraction at Japanese aquariums, are in danger of disappearing.

Only three remain in captivity, and they are too old to breed. Imports of the endangered species from the United States, their main habitat, meanwhile, have been cut off due to stricter regulations.

Undated photo shows female sea otters Kira (L) and May at Toba Aquarium in Toba, Mie Prefecture. (Photo courtesy of Toba Aquarium)(Kyodo)

In the peak year of 1994, there were 122 of the crowd-pleasing sea mammals in 28 aquariums across the country. Now only two female and one male captive otter live in two facilities.

The females are in Toba Aquarium, located in the central Japan city of Toba in Mie Prefecture. It began breeding sea otters in 1983, raising six at one point, but now has only 18-year-old May and 14-year-old Kira. Considering their average life expectancy -- around 20 years in captivity -- they do not have much longer to live.

The male sea otter, Riro, is kept at Marine World Uminonakamichi in the southwestern city of Fukuoka. He is Kira's brother and 15 years old.

"They are cute and relaxing to watch," said Megumi Iha, 29, who works in Yokohama, near Tokyo, as she gazed at them at Toba Aquarium.

"I would feel sorry for children if there were no more sea otters in aquariums," said Nao Matsuda, a 46-year-old homemaker from Mie Prefecture, who was also there.

According to the Japanese Association of Zoos and Aquariums, the first breeding facility of sea otters in Japan was Izu Mito Sea Paradise in 1982, located in Numazu in the central Japan prefecture of Shizuoka.

Becoming a huge customer draw, other aquariums decided to follow suit and keep them as well.

Kira, one of the three remaining sea otters in captivity at Japanese aquariums, is pictured with a caretaker at Toba Aquarium in Toba, Mie Prefecture, in January 2023. (Kyodo)

However, the association said, the number of captive otters in Japan shrank as difficulties cropped up with breeding and nursing. In 2021, hopes were dashed for domestic breeding when the female of the only mating pair expected to breed died.

Overhunting for fur and a tanker accident off the coast of Alaska in 1989 also led to a decline in the number of wild sea otters.

The International Union for Conservation of Nature and Natural Resources has listed them as endangered since 2000 on their Red List of Threatened Species. In Japan, the capture of sea otters is prohibited, and the last imports ceased in 2003.

Yoshihiro Ishihara, 61, who is responsible for sea otter breeding at Toba Aquarium, said "it is not clear" why the animals have had difficulty mating but suggests one possibility is that the males' reproductive capacity has declined.

Since male adult otters attack or even try to mate with their own offspring, they are generally kept in separate tanks from others, and "perhaps their instincts have waned" as a result, Ishihara said.

The most recent death of a sea otter in a Japanese aquarium was Asuka. The 23-year-old belonged to Suma Aqualife Park Kobe in Hyogo Prefecture in the country's west.

"One factor that might have contributed to her longevity is feeding her a variety of foods," said the sea otter's former caretaker Momoyo Muramoto, 40, adding she did not know what might have encouraged successful breeding.

It is not all bad news, however. Wild otters have been observed again off the coast of Hokkaido, Japan's northernmost main island.

"I want people to stop throwing trash in the sea and instead protect the environment so sea otters can live in peace," Ishihara said.