More than 4,000 people have converged on a Perth beach to protest against the WA Government's new shark culling policy.

Last month the government announced a tender for professional fisherman to use hooks on baited drum lines to catch and kill any large great white, tiger or bull sharks.

The lines would be set one kilometre from the shore of selected beaches in Perth and the South-West and would target sharks over three metres in length.

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The tough measures were announced after seven fatal shark attacks in three years.

Today's protest at Cottesloe Beach coincides with tomorrow's culling tender deadline.

Environmentalists argue there is overwhelming evidence that killing sharks will not prevent attacks.

Protest organiser Natalie Banks says the policy puts ocean life at risk and is cause for serious concern.

"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 said.

"We are ruining the marine ecosystem."

Ms Banks says several other solutions could be introduced to prevent shark attacks.

She says helicopter patrols and the tagging and tracking of sharks has helped with monitoring of shark movements.

Sorry, this video has expired Environmentalists say shark cull won't prevent attacks

"There has been a lot of talk about the success of the Twitter and SMS campaigns that Surf Lifesaving has done, as well the use of bubble curtain and using underwater sound," she said.

Ms Banks says the creation of rock pools would also ensure the safety of swimmers.

Sea Shepherd Australia managing director Jeff Hansen says sharks need to be protected, not destroyed.

"When they kill a shark, they're going to dump the body out to sea, once again bringing in more sharks. If anything, it's going to make matters worse," he said.

"A hundred shark experts and scientists wrote to the WA government and said this will not work.

"This is an expensive option and even a report done by Bond University said that this will not work."