Drum lines kill sharks

Two great white sharks captured shortly after a young surfer was attacked near Esperance were the first to be destroyed under WA's imminent threat policy.

In a departure from previous cases in which authorities failed to catch sharks responsible for biting people, the Department of Fisheries said last night it had caught two sharks but that it might be "impossible" to determine whether either mauled Sean Pollard.

The sharks, one about 3m-4.5m long and the other 3m, were captured and died on two baited drum lines the Fisheries "shark response unit" set after the attack.

Fisheries sought and got approval from the Federal Government before setting the lines.

Under the imminent threat policy, Fisheries or a delegated commercial fisherman are allowed to catch and destroy a shark that is deemed an imminent hazard to public safety - provided they get approval.

Changes brought in by the Barnett Government in 2012 to expand the definition of imminent threat also allow sharks to be killed pre-emptively if they are spotted close to popular beaches.

Although attempts have been made to catch sharks involved in attacks off WA several times over the past few years, none has been successful.

The department said both sharks would be taken back to Perth "for research purposes and further examination by the department's shark experts".

However, because it was common for sharks to disgorge their stomach contents, it would be difficult to determine whether either was responsible for the attack.

The drum lines had been removed from the water last night and a decision would be taken this morning on whether to redeploy them.