Humpback whale population bounces back

People across Australia’s east coast are catching an earlier than expected first glimpse of breaching humpback whales as they migrate north, and scientists say the reason why is a conservation success story.

Whale watchers were treated to a spectacular show in Sydney on Monday as two humpback whales surged from the water metres from their boat. Dr Wally Franklin, director of the Oceania Project, said sightings have also been reported off the coast of Merimbula, Byron Bay, Tweed Heads, the Gold Coast and Hervey Bay, as the whales journey north from the Antarctic to the Great Barrier Reef.

Prof Mike Noad, director of the centre of marine studies at the University of Queensland, said the number of sightings this early in the season, which usually peaks at the end of June and into July, is due to the eastern Australian humpback whale population booming during a remarkable period of recovery.

In the early 60s when commercial whaling was banned in the region, Noad said it was estimated only about 300 of the eastern Australian humpback whales remained. Sixty years later, he suspects the population now sits at about 40,000.

“Around 20 years ago we’d get the first one or two whales coming through about Easter time, but there was around an eighth of the number of whales that there are now,” he said. “So one or two at Easter time now becomes 16 or 30 … so every year that’s probably the same migration. It’s just there’s more whales in the population.

“It’s a wonderful success story. They got down to around 1% of the original population – 99% were wiped out. That’s how close they came to being completely wiped out.

“All we had to do was stop killing them, we haven’t done much else apart from leaving them alone … and they’ve bounced back in a really healthy way themselves.”

Noad said the last major survey of the whale population was conducted in 2015, so the estimated whale population is a “best guess”. The surveys had since been de-funded by the federal government due to the whales returning to a healthy population level.

But Noad said there is a need to continue surveying the population to understand how the whales are being affected by the climate crisis, pollution, and underwater noise and potential collisions caused by boat traffic.

In February, humpback whales were struck from the threatened species list, which drew the ire of a number of scientists due to the threats the species continues to face.

“We’ve got no idea if [the population level] is sustainable, we’ve got no idea … whether they’re going to go higher or whether they might crash if they’re outstripping their food supply,” he said.

Franklin said the whale population grew by 10% every year from the 90s to 2015.

He said drastic growth in whale populations has surprised researchers, with scientists working in the northern hemisphere who study whale populations previously thinking the maximum growth rate of whales annually was 8%.

Franklin suspects the eastern Australian whale population has surpassed this expectation due to the Great Barrier Reef being the “perfect location as a breeding area”. He said researchers have found evidence that whales from other parts of the Pacific have migrated to eastern Australia.

“The benefit of it is that whale watchers along the coast of New South Wales and Queensland get to start seeing the whales earlier, and they’ll see them longer.”