A humpback whale could have towed a vast tangle of fishing lines, ropes and buoys all the way from Antarctica before being freed off the Victorian coast.
The adult whale was first seen by helicopter crews near Loch Sport, in Gippsland a week ago but wasn't found again until Friday afternoon when it was spotted near Lakes Entrance.
The Department of Energy Environment and Climate Action established an team to prepare to remove 200 metres of rope and line, as well as 11 flotation buoys that were attached to the whale.
Incident Controller Ellen Dwyer said specialised whale disentanglement crews attached a buoy to the whale on Friday, allowing them to track its location.
On Saturday morning, the crews caught up with the whale 24km off the coastal town of Marlo, where they began the disentanglement operation.
"By Saturday afternoon, the bulk of the ropes and buoys had been removed, allowing the whale to continue its migration along the east coast of Australia," she said.
"Unfortunately, a smaller section of rope could not be removed and was still trailing from the whale."
Ms Dwyer said DEECA said initial analysis indicated the fishing equipment was from an international vessel.
"It is possible that the whale became was entangled during its summer feeding season off Antarctica and has been dragging it while it is undertaking its seasonal migration," she said.
Humpbacks migrate up to 10,000km each year from the rich feeding grounds near Antarctica to the warmer waters of northern Australia where they calve and mate.
