Risk of more entanglements on 'humpback highway' as whale population booms

From May to November every year, tens of thousands of humpback whales migrate along the east coast of Australia from Antarctic waters to the Great Barrier Reef.

There, they mate and give birth before returning back to the colder waters in the south pole.

Thousands of people pack the coastline to watch the migration and see the ocean mammals.

READ MORE: 'Incredible' close encounter with humpback as whales migrate

However, on May 19, the excitement turned to concern as a humpback calf became trapped off of Burleigh Heads on the Gold Coast.

A local diver called "Django" rescued the calf, but faced fines from the Department of Agriculture and Fisheries (DAF) for interfering with shark control equipment. These were later dropped.

Over a week ago, three more whales, including a mother and a calf, become tangled in shark nets in separate incidents on different beaches along the Queensland coast.

READ MORE: Whales freed after being caught in shark nets off Gold Coast's Main Beach

All were freed, but marine biologist and science communicator Dr Vanessa Pirotta believes it's only a matter of time before one dies.

Dr Pirotta told 9News.com.au the number of whales that have become trapped so soon in the season is unusual.

She said last year, a total of just six whales were trapped in the state's shark control equipment and all were successfully released.

"We've already seen so many entanglements early on in the year," Dr Pirotta said.

"I myself have seen firsthand whales being brought off from the shore dead as a result of drowning. Only a couple of years ago there was one off Sydney. A young calf."

Dr Pirotta said the increase in entanglements is because the population of humpbacks off the east coast of Australia is growing since commercial whaling was banned in Australia in 1978.

"They're growing around 11 per cent each year and there's over 35,000 whales in this population," she explained.

"That's a positive, but with that, we're more likely to see more animals along our east coast, so the potential for interaction with nets is high."

Dr Pirotta said shark nets and fishing gear have been placed along the "humpback whale highway", which is close to the coastline and means the naturally inquisitive animals are drawn to them.

"This gear is literally on route to where they want to go, so unfortunately the risk of interaction is there," she said.

"These nets can carry the risk of entanglements for whales, dolphins, sharks, turtles – you name it."

Call for alternative measures of shark control

Dr Pirotta said wants DAF to investigate the use of non-lethal SMART drumlines as an alternative means of shark control. These drumlines are anchored to the floor and send an alert to officials once an animal is caught on the line.

"As scientists we need to manage a growing whale population which interacts with some of Australia's biggest cities on the coast," she said.

However, DAF has defended its current shark control measures saying there has been just one fatality at a protected beach since 1962, while entanglements remains uncommon.

"There are tens of thousands of whales moving along our coastline, but whale entanglements remain relatively rare incidents," a DAF spokesperson said.

"Protection of human life always comes first – that's why we have a Shark Control Program."

DAF said it is looking into "options" to reduce the risk of other whales getting trapped as the migration increases.

"The Queensland Government understands that many people have strong views about shark control, and is considering scientific advice about replacing shark nets with drumlines during the whale migration season," the spokesperson said.

"Maintaining the safety of swimmers remains the key priority, but where possible we will look at options to reduce unintended impacts of shark control equipment on other marine life.

"Our specialist team trains for such events, and with the support of Seaworld we have a great record of successfully releasing whales.

"We also have a range of monitoring activities, including our volunteer observers, which help us to spot any whale entanglements early."

Contact Raffaella Ciccarelli at rciccarelli@nine.com.au