The growing humpback whale population much celebrated by conservationists in Australia seems to be attracting more killer sharks and threatening surfers and beachgoers.
Alarmed by evidence from fishermen and some scientists that a spate of shark attacks may be linked to annual whale migrations along the Australian coastline, Malcolm Turnbull’s government has ordered an inquiry.
“I want to understand better . . . what’s happening with whale numbers because I understand whale numbers have increased and the great whites are feeding off the carcasses,” Josh Frydenberg, the environment minister, said. “The feedback from the commercial fishing industry is that great whites are going right up to their boats and numbers have increased significantly.”
The whales migrate along Australia’s east coast, past the popular surfing beaches in northern New South Wales, which have seen a surge in shark attacks. Surfers on those beaches, like their counterparts in Western Australia, have also observed rising numbers of great whites.
“The cold hard reality is that their numbers are increasing — there’s no way anyone can dispute that,” Don Munro, the president of Lennox-Ballina Boardriders in New South Wales, said. “Due to the increasing numbers, a cull should be a forgone conclusion.”
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Scientists reported last month that a long-term hunting ban may have resulted in humpback whale numbers rising beyond their estimated historical highs in Antarctic and Australian waters.
Michael Noad, an associate professor at the University of Queensland and an expert on humpback whales, said that the numbers suggested that more than 30,000 humpbacks would migrate up the Australian east coast this year, roughly matching peak historical numbers.
These figures are considered remarkable given that hunting reduced the population migrating along Australia’s east coast to a few hundred before a hunting moratorium was declared in 1966.
A study published in the Medical Journal of Australia in 2014 concluded that shark attacks would continue to rise in line with increasing whale numbers because whales were a food source for the predators. Sharks scavenged whale carcasses, the report said, and whales contributed “the most by mass” to large white shark diets.
Mr Frydenberg said that he had directed Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) to report on the link between whale and white shark populations.
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White sharks — the species most commonly involved in attacks — have had protection in Australian waters since the late 1990s, but the Turnbull government has commissioned a survey of their numbers as a precursor for a possible attempt to delist the species as threatened.
Such a move would be complicated; the sharks are protected under the UN Convention for the Conservation of Migratory Species, which would require two thirds of voting members to change their minds.
In a submission to an Australian parliamentary inquiry into possible measures to curb shark attacks, the CSIRO said that because there were no reliable estimates of shark numbers it was impossible, for now, to say whether their numbers were increasing.