The abandoned baby whale that had been in waters off north Sydney, for the past week has now been euthanised to spare it further suffering.

The humpback whale, nicknamed "Colin" but later found to be female, was discovered attempting to suckle from a moored yacht at Sydney's Pittwater Bay after being possibly abandoned by its mother off Australia's east coast.

After a six-day effort to lead the calf back to open sea and reunite it with other migrating humpbacks, rangers and scientists decided that it would be more humane to destroy the whale.

Veterinarians and marine researchers spent time examining the whale and sadly it was in much worse condition than originally thought. It had injuries which looked like they were from a shark attack. The whale dominated news coverage worldwide since it was first sighted.

A spokesperson for Marine Connection comments; "This whale was very young, weeks old, and starving. It should have been feeding on its mother’s milk, taking in litres per day but not having fed for days, it would have lost weight rapidly. Humpback milk is 50% fat and quickly adds weight to the infants to enable them to continue long journeys. It wasn’t as simple as taking the calf back out to sea as it would have been completely dependant upon its mother at the moment."

Although everyone had fallen in love with this little whale, the animal's welfare was priority.