Paton said the whales are heading from the Antarctic to warmer breeding grounds and a team from the centre and Australia's National Parks and Wildlife Service had counted 591 whales off Byron Bay, New South Wales in the last week of June and first week of July.

Last year over the same time, officials counted around 572.

"We are seeing a general increase in the number of animals," Paton told Reuters.

He said combining records from other studies showed that the humpback whales population is growing around 10 percent a year.

"That's pretty good to see," he said.

Humpback whales, which weigh 25 to 40-tonnes and can grow to more than 15 metres (48 feet), numbered between 15,000-20,000 in the South Pacific off Australia's east coast before hunting reduced them to just 200-500 by the 1960s, when they became protected.

Based on the surveys being conducted off Australia, Paton said it was estimated that the population had recovered to 4,500-5,000.

But he said it was too early to say the whales were off the endangered list.

Studies have found high amounts of heavy metals and other industrial contaminants in their blubber, while their main food source, a small shrimp-like crustacean called krill, is being harvested and global warming may be affecting their habitat.

"They may not be endangered but they're certainly still being impacted," Paton said.