Leighton and Port beaches were closed this morning and Fisheries Department officers set more drum lines after a 4m shark was spotted a few hundred metres off Leighton beach.
Surf Life Saving WA reported that a 4m shark was swimming south about 100m off North Leighton about 8.30am, as hoards of people began arriving for surf club.
The alert prompted the fisheries vessel, which had been returning from Mullaloo after inspecting Perth drum-lines, to rush south.
Swimmers and surfers were still in the water despite the warning.
After arriving at Leighton, officers set extra drum-lines at the southern corner of the beach in a bid to catch the shark, the species of which is unknown.
The beaches were later re-opened after no further sightings of the shark.
All 10 drum lines were checked earlier this morning but all were clear.
On Friday the lines were deployed for the first time off the metropolitan coast under the Barnett Government's shark catch-and-kill policy.
Four tiger sharks, all under the 3m limit. have been caught in the first three days since the lines were set off metropolitan beaches.
Of those, three have been released and the other was dead when fisheries officers arrived.
A dead 2m-long shark was dumped about 15km offshore yesterday as hooks were being checked hours before thousands of people rallied at Cottesloe Beach this morning.
The shark, believed to be a tiger shark, was pulled aboard about 6.45am off Leighton Beach.
A second shark was pulled up and released off Scarborough Beach at 10.35am.
About 6000 people descended on Cottesloe Beach yesterday to protest against the State Government’s shark-kill policy.
They stood shoulder-to-shoulder on the sand, terraces, stairs and in the car park united in their opposition of the drum lines 1km offshore.
The beach was transformed into a sea of placards by 10am, dotted with women in mermaid costumes, men dressed up as sharks and a cardboard cut-out of Premier Colin Barnett hooked on the end of a fishing rod.
Police on horseback watched over the rally and a plane circled overheard towing a banner that said “Great Whites have rights #nosharkcull.”
Chants rang out between the speeches, including, “It’s their water, stop the slaughter,” and, “Two, four, six, eight, we don’t want your bloody baits.”
At one point, the crowd turned around to face the Fisheries boats as they travelled past, shouting, “Leave our sharks alone.”
A couple of pro-policy protestors arrived to a chorus of boos, but they were outnumbered 3000:1 by a mix of teenagers, families and seniors.
Former journalist and shark expert Hugh Edwards addressed the protest, labelling the Barnett Government’s catch-and-kill policy a “waste of everybody’s time".
“That policy has failed dismally as you can see by the number of people here,” he said.
“It’s going to cost between three and five million dollars for the first year and it’s not going to prevent attacks.
“All of the fatal attacks in WA since the year 2000 have been great whites and great whites of major size.
“When we had the five attacks two years ago, two people were totally consumed, two were bitten in half and the fifth would have been consumed if they hadn’t got the remains into the boat.
“That indicates there’s a shark of five to six metres, species great white, and we need to know more about great whites.”
He said the money would be better spent on scientific studies, such as working with the US group Ocean Search.
Protest organiser Natalie Banks said the money should go towards tagging, helicopter patrols, the eco-barrier trial at Coogee Beach and shark shield technology.
Labor leader Mark McGowan slammed Mr Barnett for wasting all the good work the Liberal Government had done on shark attacks before the introduction of drum lines.
He said the current policy was a waste of money that could be spent on tagging or other pressing issues including mental health.
“I am absolutely certain that every person here today values human life and I am absolutely certain that every person here today also values our beautiful, diverse, wonderful ocean,” Mr McGowan said.
“It does not need to be a choice between the two.
“If offends me when I see people on the television like Troy Buswell making out as though if you object to this, you don’t value human life.”
Sea Shepherd managing director Jeff Hansen said the Government was forcing the Fisheries Department to carry out a cull it did not support.
“Look what the Barnett Government is making our Fisheries Department do,” he said.
High Wycombe mother of three Christine Maynard, 57, questioned why the Government would remove the drum lines before the Rottnest Swim.
“Why are they pulling them out for the Rottnest Swim? Does that mean it’s dangerous in the water at the moment,” she said.
“This isn’t based on any scientific facts - it’s just a knee-jerk reaction and it makes it so much less safe. I wouldn’t take the kids out there if I still had young kids.
“(Barnett) should listen to the people. He should listen to what the every day, ordinary people have to say.”
Dino Colica, a 36-year-old from Bibra Lake, was at Cottesloe with his wife and child, protesting against the “draconian” policy.
“Obviously Colin Barnett’s stance on this is very arrogant. He’s not listening to the general public of WA so this is the only way we figure we can help by supporting the activists,” he said.
“This isn’t just activists or hardcore protestors, it’s the general community.”
Peter Newman, 25, made the journey from Butler with his family to join the rally against the shark-kill.
“It’s a barbaric thing to do. Why can’t they tag the sharks and then monitor and research them,” he said.
“If someone goes on a safari in Africa and they get attacked by a lion, you don’t say, ‘Oh well this isn’t good enough, we’ll have to have a cull.’
“You’re going into their territory, just like you’re going into the shark’s territory.”
The Australian Greens told protesters at Cottesloe that the catch-and-kill policy must end immediately because "drum lines along the Perth coast target threatened species and vulnerable marine life".
"This is appalling, cruel and illogical marine policy," Greens leader Senator Christine Milne said.
"The drum lines kill indiscriminately and we have seen sharks being brutally slaughtered off our beaches.
"The Premier should admit he was wrong and end the cull immediately.
"The ocean is the sharks' home. We here recognise that. Mr Barnett should too."
The Greens' marine spokesperson, Senator Rachel Siewert, will present a petition to the Senate in coming weeks with the names of more than 79,000 people opposed to the Government's policy.
"There has been a passionate response from people around Australia and around the world to this cull," Senator Siewert said.
"The WA and federal governments will be held to account for reckless, knee-jerk policy making.
"Drum lines are indiscriminate and threaten a range of marine animals.
"We've already seen undersized sharks caught, and WA's other marine life is under threat.
"Strong, non-lethal policy options exist that can educate and protect the public, including monitoring, tracking and tagging, and personal deterrent technologies."
A 19-year-old woman was issued with a move-on notice and is expected to be summonsed for trespassing after an incident at Fremantle boat harbour this morning.
The Fremantle woman had attached herself to Department of Fisheries vessel about 4.30am.
The Department of Fisheries denied protesters' claims that the boat's departure was delayed by two hours.