It used to be a pit stop on the humpback migration highway but marine experts say the Gold Coast is becoming a whale nursery, and no-one is sure exactly why.

Key points: Traditionally humpbacks give birth in areas along the Great Barrier Reef, but researchers have noticed a shift 1,000km south

Traditionally humpbacks give birth in areas along the Great Barrier Reef, but researchers have noticed a shift 1,000km south 74 newborn whale calves have been spotted in the Gold Coast Bay between 2013 and 2016

74 newborn whale calves have been spotted in the Gold Coast Bay between 2013 and 2016 Whale numbers are increasing at 10.9 per cent per year, according to the University of Queensland

Cows traditionally give birth in areas along the Great Barrier Reef, but researchers have noticed a shift 1,000 kilometres south.

Researcher and marine educator, Laura Torre-Williams, said it was a huge behavioural change.

"There are supposed to be zero being born and sighted here," she said.

"We are seeing these bubs here on the northern migration and the mothers are meant to be giving birth exclusively in the Great Barrier Reef so something definitely is changing.

"They really are newborns: they are floppy, they are barely able to swim, we'll see them often being carried by their mothers on her back, their tails will still be curled."

A study undertaken by Griffith University, commercial whale watching operators and research group Humpbacks and Hi-Rises, observed 74 newborn whale calves in the Gold Coast Bay between 2013 and 2016.

Research is now starting to focus on the movements of the calves via GPS tracking and the early results have been surprising.

"Their direction of travel seems to be to the north, which is something new again," Ms Torre-Williams said.

"Newborn humpback whales aren't supposed to have a good swimming capability and yet we are seeing them swimming north across the bay."

'We have to consider global warming'

A mother swims with a newborn baby calf off the Gold Coast as researchers discover more babies are being born further south. ( Supplied: SeaPix Photographics )

Changing ocean conditions are considered the most likely reason for the new calving patterns.

"It could have to do with the food supply in Antarctica and the whales aren't able to feed as well or have to travel to different locations which might affect their timing," she said.

"We also have to consider global warming and climate change and that the Gold Coast Bay water may be just warm enough for the mothers to go ahead and give birth here so these conditions may be becoming suitable for calving habitat."

The whale watching season officially starts in June, however, humpbacks have already been spotted off Bundaberg and the Fraser Coast and a larger pod has been seen near Byron Bay.

Tweed Heads-based whale watching operator, Dave Jaeger, said he has noticed the season starting earlier and earlier each year.

He believes it can partly be put down to booming population numbers, which the University of Queensland has tracked at a 10.9 per cent increase per year.

"There are so many more of them and they're like naughty school kids now," he said.

"They are becoming cheekier each year, we have to keep our boats 100 metres away from them but they come to us and 'spy hop' right beside the boat.

"Their spatial awareness is unbelievable too.

"We have had whales splashing their tail at snorkelers — they are being playful and know exactly where everyone is."

Researchers have asked locals to keep an eye out for sick or injured whales. ( Supplied: Humpbacks and Highrises )

Increasing traffic on the "humpback highway" has also raised safety concerns, with recreational boaties cautioned to keep their distance, especially from resting calves.

Jasmine Rasmussen from research group Humpbacks and Highrises said the public could also play an important role in monitoring whale health.

"The best thing to do as they are travelling up the coast this year is to have a look out for whales and if you think their skin pigmentation looks a little bit different or they appear to have wounds on their back even from boat strikes or perhaps a netting injury, then reach out," Ms Rasmussen said.

"A sick whale was spotted off Byron Bay a few days ago.

"It is vital for research that we take note of this sick whale and get anything we can from it to learn about what is happening to the poor whales as they are travelling up the coast line."