Footage of the doomed whale up against a boat
A baby whale abandoned by its mother in the waters off north Sydney has been put down, after veterinarians decided it could not survive on its own.
The humpback whale calf had been trying to suckle from boats, which it apparently mistook for its parent.
The plight of the starving two-tonne animal, dubbed Colin, has captivated Australia since last weekend.
The whale was first given a sedative, then a lethal dose of anaesthetic, which took 10 minutes.
"It's a tragic end to a programme that dozens of people have put their hearts and souls into," National Parks and Wildlife Service official John Dengate told Australian radio.
The calf had suffered shark bites and was having trouble breathing
A vet report and blood tests on Thursday had revealed the calf, believed to be only two to three weeks old, was suffering from shark bite wounds and breathing difficulties.
The plight of the baby whale has transfixed the country and only the action from the Beijing Olympics has been a rival for the attention of the Australian public, says the BBC's Nick Bryant in Sydney.
A number of attempts had been made to lure Colin out to sea, where it was hoped he would have been adopted by a lactating female.
The National Parks and Wildlife Service said in a statement this week that there was no way of feeding the calf in captivity as it was still being breast fed.
Australia's navy had offered to attempt to tow the 14-ft-long (4.5-metre-long) animal away from the shore using a fuel bladder as an inflatable sling.
Colin had not eaten for a week and whale calves need up to 230 litres of milk a day, say experts.
An Aboriginal "whale whisperer" was brought to the bay on Thursday to "talk" to the calf.
"He heard me singing and came over. I looked at him and he was full of life... All he needed is a mother's milk," Bunna Lawrie told the Sydney Morning Herald newspaper.
The whale was first sighted on Sunday just north of Sydney at Pittwater and soon began to try to suckle from a yacht, which it would not leave.
The humpback whales are on the return leg of an annual round trip from the Antarctic to tropical waters to breed. They can often be seen quite close to Sydney's beaches.