The growing number of humpback whales migrating along the New South Wales north coast is bringing a corresponding rise in attacks by alpha predators.

Alpha predators, or apex predators, are those creatures at the top of the food chain, like orcas.

The southerly migration of humpbacks is currently underway, from warm water breeding grounds in Queensland to summer krill feeding in the Antarctic.

Ronnie Ling, from the marine mammal rescue and research organisation ORRCA, said in recent weeks there had been a number of sightings of orcas also known as 'killer whales'.

Orcas seen hunting humpbacks

Orcas are the largest species of dolphin and are easily recognised by their distinctive black and white markings.

They typically hunt in packs of three to 40 individuals.

"We've had them this year from Byron Bay down to South West Rocks [and] we believe it was the same pod," Mr Ling said.

"The sightings were about a day and a half apart and both times, they were observed hunting humpbacks.

"A couple of days later, we actually had some humpback pieces wash up at Byron Bay, which showed rake marks, evidence orcas had been at them.

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"These animals travel very fast and in very varied areas around the place.

"A lot of the times they are following the whales and the seals through migration periods [and] they target the younger or the weaker, older, animals in the pod of whales."

Professor Peter Harrison, director of the Southern Cross University (SCU) Ideas Research Institute and a leading cetacean researcher, said there had been a massive increase in humpback numbers.

"It is nationally significant because it is one of the few examples of a mammal in Australia that has actually increased," he said.

"Most are decreasing and many have become extinct.

"The extinction rate hasn't changed in decades and we're still losing, on average, about two mammal species per decade."

Australia 'going backwards' in marine research: scientist

Dr Harrison said humpback whale numbers were recovering along the coast after being decimated by illegal Soviet whaling.

"Remarkably they've come back again really strongly this year [and] we are thinking there are between 30,000 and 33,000 migrating along our coastline," he said.

"It's one of the good news stories about conservation success in Australia."

Dr Harrison said recent sighting of orcas off the north coast highlighted the gap in funding for marine mammal research.

Orcas, like these photographed by WA's Project ORCA, are believed to have been feeding on migrating humpback whales on the NSW north coast (file photo). ( Submitted: Rebecca Wellard )

He said not enough was known about orca species migrating along the NSW north coast and funding for such research had been terminated and not reinstated.

"It used to be a highlight of some of the research investments that were done through the Department of Environment," he said.

"At the moment, Australian researchers who are trying to get funding for marine mammal work are really struggling to get even basic funding.

"We're going backwards in terms of our knowledge base about these amazing animals.

"We only really know a fair bit about humpback whales, southern right whales, bottlenose dolphins and suchlike.

"We're totally ignorant about most of the other cetacean species that occur in Australian waters.

"We absolutely need to understand these because they are a pivotal aspect of our marine ecology."

Western Australian PhD candidate at Curtin University, Rebecca Wellard, has been working with Project ORCA.

They are studying orca populations off Australia's west coast and are working closely with Killer Whales Australia who are looking at east coast populations.

Ms Wellard agrees that more funding is critical to help better understand these elusive sea creatures.

Predators responding to increased food

Dr Harrison said it made sense that there were now more orca sightings.

"The health of our marine eco systems is partly indicated by the top predators [and] we're starting to lose those top predators," he said.

"There has been a massive decline in sharks through shark-finning that's been going on in most places around the world.

"What is good to see is that some of the top predators, such as the orca, are responding to increased food supply [although] we don't know whether or not their populations are responding.

"Presumably, they would have declined as the humpback whale sources declined in recent decades.

"As humpbacks have started to increase, we'd hope to see a similar response in orca populations but there is currently no money for such research."

These orcas were spotted as part of Western Australia's Project ORCA research (file photo). ( Submitted: Rebecca Wellard )

Orca activity unusual on mid-north coast

A dive group off South West Rocks, east of Kempsey, recently had an unusual experience when they spotted orcas hunting a pod of humpback whales.

Dive operator Steve Skinner said sea conditions at the time made it hard to see if the humpbacks had escaped the attack by about six orcas.

"It was a bit rough [and] we were bouncing around a bit so we couldn't actually stay to watch the full hunt," he said.

"There were three big humpbacks, two adults and their little calf, so hopefully they were able to fight them off.

"In the eight years I've been driving for the South West Rocks Dive Centre I've never actually seen orcas out there.

"I've known them to be around the area but never actually seen them for myself off the rocks there.

"It was extraordinary to see, everyone on the boat was very excited to see it."

Mr Ling said it was likely the orca pod spotted off South West Rocks was the same one seen off Byron Bay.

"Of course we know our whale species are rising in numbers, we're finally starting to get whales coming back so naturally, the predators are going to pick up as well," he said.