Thousands protest WA's government shark strategy

The West Australian government has come under fire for recently stepping up the measures after a spate of fatal attacks in WA waters, with plans to set baited hooks one kilometre offshore from this month.

Up to 72 baited hooks will be used to catch and kill sharks at five popular Perth beaches and three in WA's South West under the state government's controversial new "mitigation" policy.

Protest organiser Natalie Banks says the policy will not prevent shark attacks and puts marine life at risk.

"There is going to be other marine life caught in the bait lines, not just sharks and there's going to be sharks under three metres also caught in the bait lines," she told the ABC.

"We are ruining the marine ecosystem."

Mr Barnett has defended the state government's strategy, previously saying the new measures are necessary after a surge in shark activity in the state's waters in recent years.

"We have had 20 fatal shark attacks in WA in the past 100 years - seven of them in the past three years," he said.