The phenomenal growth in the humpback whale population has resulted in some of the giant beasts of the ocean beginning their migration north almost a month early.

Whale-watching season for tourism operators such as the Sunshine Coast's Whale One traditionally begins on the first weekend in June.

But a number of sightings off Caloundra and Alexandra Headland in the past two weeks has prompted Whale One owner John Matterson to bring his season forward by a week.

"The whales have come up very early this year," Mr Matterson said.

"There have been quite a few reports and particularly ones in close from Caloundra to Point Cartwright and Alexandra Headland. It is very unusual."

Southern Cross University Marine Ecology Research Centre founding director Peter Harrison said whales were moving earlier because their numbers had grown so large.

Whale numbers were decimated between 1959 and 1961, mostly by illegal whaling, until there were only a "couple of hundred left".

This season, about 33,000 whales are expected to make the 5,000km migration north from the Antarctic to Queensland's warm tropical waters.

Whale population grows to highest level

Professor Harrison said the humpback whale population had grown so large, it was now the biggest it had ever been.

"As far as we know, the population is now larger than it was prior to whaling," he said.

"Researchers have gone back to look at catch records and our best estimates are the whale population [pre-whaling] was hovering around 26,000 for the natural population size.

"That was almost completely decimated, mostly by illegal whaling from a Soviet fleet which was estimated to have killed 25,000 whales between 1959 and 1961.

"After this, there were possibly only a few hundred whales left and there was almost total extinction."

In 1962 the whaling stations at Tangalooma, on Moreton Island and in northern New South Wales were closed and there were not enough whales left to make whaling viable.

The population has grown steadily every year, but Professor Harrison said it would start to slow, and there was no concern it would grow too big to be sustainable.

"What will happen is the rate of population increase will start to slow and come back to a normal level of growth," he said.

Whale-watching boats have to stay an extra 500m away from any white whale in NSW. ( Supplied: Jodie Lowe's Marine Animal Photography )

Migaloo gets a wide berth

Office of Environment and Heritage wildlife team leader Susan Crocetti said there were increased distances for Migaloo in New South Wales this year to give him "a bit of extra space that he gets in Queensland".

"We actually believe that there is more than one Migaloo out there, so we anticipate we will get news of a white whale any day now," she said.

"We think we might have up to three, maybe even five white whales that migrate up the coastline, and we have an extra distance of 500 metres for any white whale.



"We just think it's an unusual colour morph of a whale and they're just predominantly white whales. I think Migaloo is still sort of regarded as a unique solely white whale, but we do have other whales that are predominantly white."

Killer-whale sightings increasing

With the recovery of humpbacks also comes other whale species that are associated with humpbacks, such as killer whales.

"We've had quite a lot of reports in the last few weeks of killer whales being seen off the coastline," Ms Crocetti said.

Killer whales follow the migration of humpback whales, particularly targeting females and calves. ( Supplied: Craig Sargent )

"Killer whales have always been around, but in terms of the frequency and the numbers of humpbacks being seen, it certainly does seem to be an increasing trend how many we are observing.

"They will try to prey upon humpback calves. Killer whales tend to love tongues, so sometimes we might get footage of a humpback whale calf that's unfortunately been attacked by killer whales and they'll only take the tongue, which is just amazing."

Craig Sergant, a commercial skipper in Port Macquarie, said orcas predominantly liked to chase female whales with their newborns.

"Those females generally close very close to the coastline with their calves, so the orcas have to come in close to find those," he said.

"I've found a calf offshore here at Port Macquarie that we assumed the orcas had only just left the calf and removed its jaw.

"We're lucky in Port Macquarie because through the mid-season we've got whales going in both directions for about four weeks."