SHANGHAI, Feb. 28 (Xinhua) -- A Shanghai ocean park said Thursday that its most popular stars, two female beluga whales, were being prepared to be relocated to an open water sanctuary in Iceland, about 9,000 km away, this Spring.

"Little Grey" and "Little White," both 12 years old, made their final public appearance at the Changfeng Ocean World on Thursday, attracting many fans to bid farewell, according to the park.

The park said the duo would take a 30-hour-plus journey by air, land and sea to arrive at the Sea Life Trust Beluga Whale Sanctuary.

The sanctuary was created by the Sea Life Trust and Whale and Dolphin Conservation, in a bay at Heimaey Island, located off the southern coast of Iceland.

Sea Life Trust said on its website that the two whales would be the first residents in the sanctuary, which encourages the rehabilitation of captive whales into their natural environments.

The departure date will be settled according to the physical condition of the whales and other factors such as weather, the park said.

The whales have been trained to improve their physical abilities and swimming skills in open water in the past few months. They will also receive special training to prepare for aquatic plants and animals in their new home, according to the park.

Special menus have also been prepared for them to gain more fat and weight to adapt to the cooler water at the sanctuary. The park said both whales had gained 90 kilos in weight to reach nearly one ton.

At nearly 4 meters in length, the whales have become the most welcomed animals in the park since their arrival in April 2011.