Harmless sharks and endangered species are among a haul of marine life unintentionally caught in other parts of the world by the same type of drum lines soon to be cast off WA's coast.
Less than 18 per cent of marine life caught on drum lines in South Africa in the 2011 to 2012 financial year have been great white or tiger sharks, according to statistics published by the KwaZulu-Natal Shark Board – the unit responsible for maintaining the lines in that province.
On January 10, WA's first lot of drum lines will be set in designated areas along WA's coast. Any great white shark, tiger shark or bull shark captured that is greater than three metres will be shot.
The lines are in response to six people being killed by suspected great white shark attack off the WA coast since September 2011.
Greens South Metro MLC Lynn MacLaren says that examination of the KwaZulu-Natal Shark Board annual reports reveal unacceptable collateral damage.
"The WA Government has justified its unpopular new shark cull policy by citing experiences elsewhere, yet an examination of the few places in the world where drum lines have been introduced shows that drum lines kill far more harmless species than they do tiger and great white sharks," Ms MacLaren said.
"In most cases, the capture of small, harmless sharks has led to their deaths; the sharks have suffocated because once caught on a drum line hook they cannot move sufficiently to pass water over their gills and receive oxygen," Ms Maclaren said.
According to the South African report, a humpback whale and an endangered leatherback turtle were among 97 animals caught by drum lines since their installation in February 2007. Some of the animals are released, while others don't survive.
On Thursday, more than 100 shark scientists signed an open letter to the WA Government calling for non-lethal measures to be used to protect beach-goers, along with a greater investment in research and monitoring.
A 1997 peer-reviewed comparison study of shark control programs in New South Wales, Queensland and South Africa - where large gill nets and drum lines are used – found the total number of shark attacks at meshed beaches was reduced.
Meanwhile, a Bond University study that was commissioned by the WA Government last year on the best shark hazard mitigation study for WA, recommended against the use of drum lines.
Ms MacLaren said it was noted in the Bond study that the unintended catch of harmless marine species, including dolphins, would be especially high within the first years that drum lines were deployed – in other words, until the local populations of those species had been reduced.
"I suspect that this and the slow, cruel death that drum lines cause are the real reasons that the Premier has hinted that he will not allow the public to see the captures on drum lines if they are deployed."