An orphaned killer whale which turned up off the coast of Seattle last January has been released to find her family group after a complex operation to bring her back to Canadian waters.

Her calls were so loud they practically blew our earphones off

Aquarium official Lance Barrett-Lennard

The two-year-old whale, officially named A-73 but nicknamed Springer, bolted to freedom after being released from a temporary holding pen.

She had been brought to Telegraph Cove in British Columbia after a journey of nearly 12 hours, riding semi-afloat in a special container on board a high-speed catamaran.

Scientists say they are optimistic Springer, who called loudly to the 20 to 30 whales in her family group, will be permanently reunited with them.

"Based on what we saw...we were quite sure that when we opened the gate, she'd go charging off, and she did," said John Nightingale, president of the Vancouver Aquarium.

Sound is very important to whales, with different family pods using distinct sounds and calls to communicate.

This is one of the first attempts to reunite a wild orca whale - as killer whales are also known - with its family group.

Tourist attraction

The 545 kilogramme (1,200 pound) whale attracted international attention since being discovered swimming in the busy shipping lanes of Puget Sound, near Seattle, in poor health.

She spent at least six months in Puget Sound, often swimming beside the passenger ferries going to and from Seattle.

Easy does it...the complex operation took weeks to organise (AP)

Scientists believe she became lost after being separated from her family group, or pod. Alternatively, she could have been rejected after her mother died.

The scientists decided to capture her to nurse her back to health, partly because she was becoming too friendly with boaters in the area, raising fears that she could capsize a small vessel as she grew.

US and Canadian officials worked together to arrange the relocation, which cost upwards of $200,000.

New home

On Saturday morning, a large crane winched the whale onto a specially constructed pool on the catamaran.

Springer has been compared to Keiko - star of the movie 'Free Willy'

During the journey, whale handlers covered Springer's upper body with wet towels and put ointment on her dorsal fin and around her blowhole to keep her skin moist.

On arrival in Telegraph Cove, she was lowered into another sea pen before being set free.

Whales that were in the vicinity included members of her birth pod, said aquarium official Lance Barrett-Lennard, who said it was clear Springer knew she was in home waters.

"Her calls were so loud they practically blew our earphones off," he said.