Sharks being mauled on WA drum lines

More than 30 sharks are thought to have been caught on drum lines in West Australian waters, while some are being mauled by larger prey, prompting the Greens to call for an end to the controversial shark kill policy.

Bull, tiger and great white sharks longer than three metres that are caught within one kilometre of parts of the WA coast are being shot dead and discarded at sea.

The policy was implemented after federal Environment Minister Greg Hunt granted an exemption so the protected great white shark could be killed.

Greens Senator Rachel Siewert wants Mr Hunt to revoke the exemption and will move a motion on Wednesday claiming the state government is breaching conditions set by catching small sharks.

She said at least 36 sharks had been caught since the drum lines were set up, 32 of which were undersize.

The state government has not officially revealed the number or type of sharks being caught.

"We don't know how many of these undersized sharks are dying once they are released," Ms Siewert said.

"Reports of mauling by other sharks, along with the damage done by the hook means that animals could be seriously harmed."

A spokesman for the WA Department of Premier and Cabinet confirmed both the fishing contractor in the South West and the Fisheries crews had reported "minor evidence" of bites on sharks caught on the lines, which were probably from other sharks.

"These incidents are in a minority in the South West and only one incident has been noted in the metro area," he said.

Meanwhile, drum lines were set off Yallingup and Gracetown, in the state's South West, on Tuesday morning.

Previously, drum lines had been deployed only from Dunsborough to Meelup Beach.

Gracetown is where Chris Boyd was fatally attacked in late 2013, which prompted the controversial shark kill policy.

It was the seventh attack in WA waters since August 2010, and came only a month after abalone diver Greg Pickering was mauled.