The last Indo-Pacific bottlenose dolphin kept in a South Korean aquarium has been released into the wild after 17 years following monthslong rehabilitation training, the oceans ministry said Monday.

Bibong was set free on Sunday from a pen in the sea off South Korea's southern resort island of Jeju, where he had stayed for about 70 days for training to adapt to the new environment upon the government's release plan, according to the Ministry of Oceans and Fisheries.

Experts said Bibong, a male dolphin believed to be 23 years old, was believed to have been fully ready to return to the wild.

The dolphin had been kept in a marine mammal park on the island after being illegally caught in waters off the island in 2005.

He was the last marine mammal of his kind in captivity, as the country had released seven Indo-Pacific bottlenose dolphins into the sea since 2013 after designating the species as priority marine life the previous year.

The ministry said it attached a positioning device to Bibong's body for regular monitoring at least for about six months.

"Bibong was finally able to return home after 17 years. The government will continue to seek measures to improve the welfare of marine animals," Minister Cho Seung-hwan said.

Other than Bibong, a total of 21 belugas and other kinds of dolphins are currently at domestic aquariums, all of which have been kept after going through legal procedures for research or other purposes, according to the ministry. (Yonhap)