An orphaned killer whale which turned up off the coast of Seattle last January finally arrived back in Canadian waters after scientists mounted a complex operation to take her home.

The two-year-old whale, officially named A-73 but nicknamed Springer, arrived at 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.

She will be housed in an offshore holding pen until her release into open water, when scientists hope she will be reunited with her family.

We will have done the human part. When she leaves it is up to the whale

John Nightingale, Vancouver Aquarium

"We're certainly not going to release her until tomorrow (Sunday) at the minimum, because we want to do so during daylight," said John Ford, a scientist with Fisheries and Oceans Canada.

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

Officials have spent weeks struggling with medical and logistical issues, and a last-minute technical hitch on Friday delayed the return further. But Saturday's operation is said to have gone smoothly.

Tourist attraction

The 545 kilogramme (1,200 pound) whale has 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.

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

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 and also 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 is costing upwards of $200,000.

New home

On Saturday morning, as news helicopters circled overhead, a large crane winched the whale out of her holding pen in Seattle and into a specially constructed pool on the catamaran.

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. She will be monitored for any sign of stress or ill health before being released to hopefully reunite with her family.

Sound is very important to whales, with different family pods using distinct sounds and calls to communicate. It is hoped that Springer and her family will recognise each other through these sounds.

But there is no guarantee that she will be accepted back into the tightly knit orca clan.

"We will have done the human part. When she leaves, it is up to the whale," said John Nightingale, president of the Vancouver Aquarium.