Fuji, a mother dolphin that lost 75 per cent of its tail due to a mysterious disease, is jumping once again with the help of what is believed to be the world's first artificial fin.

The 34-year-old dolphin held at Japan's largest aquarium wears the rubber fin for about 20 minutes a day, allowing her to jump and to swim at the same speed as other dolphins.

Masaya Kowami, a breeder at Okinawa Churaumi Aquarium on the southern island of Okinawa, says Fuji's handlers are "grateful".

"Although she can swim without the artificial fin, the speed is very slow and she certainly cannot jump without it," he said. "Visitors have told us she looks happy."

Fuji initially rejected the artificial fin, which in its current version weighs two kilograms and is 48 centimetres wide.

The breeders decided not to keep Fuji's fin on all day, fearing that it may fall off and be eaten or destroyed by other dolphins.