More than 40 sharks a week were reported off popular Perth and South West beaches in the past seven months, including almost 10 a day since spring.

Figures from Surf Life Saving WA show a big increase this year in the number of sharks spotted by aerial patrols that run from September to April.

SLSWA said that until December 17, 184 sharks were spotted by Westpac helicopters, compared with 107 by the same time last year.

Of those sightings so far this year, 82 prompted “immediate action” to close patrolled beaches or issue alerts to swimmers via the helicopters’ alarms at unpatrolled beaches.

Despite the jump in the number of sightings by the aerial patrols, SLSWA said overall reports of sharks had decreased about 20 per cent year on year.

Since May there have been 1414 shark reports, which include public sightings, aerial surveillance and, most frequently, detections by State-owned acoustic receivers scattered around the Perth and southern coastlines.

The most commonly encountered species was bronze whaler, which accounted for 42 per cent of reports, followed by white pointers at 21 per cent and tiger sharks at 17 per cent.

Camera Icon Shark sighting at the Mullaloo Club. Credit: SLSWA

Unknown species made up 18 per cent of reports.

Quindalup boat ramp near Dunsborough had the highest number of reports at 12, followed closely by neighbouring Toby Inlet, which had 10, and Bunker Bay at eight.

In the metropolitan area, Point Peron at Rockingham was the most likely spot for a shark to be seen or detected, with eight reported.

At Rous Head in Fremantle, six sharks were reported, while City Beach had five.

Play Video The imposing shark seemed barely smaller than the 8-metre boat it was circling, when it was caught on camera in WA's south. The West Australian Video The imposing shark seemed barely smaller than the 8-metre boat it was circling, when it was caught on camera in WA's south.

By far the most commonly spotted size of shark by aerial patrols was between 2m and 3m, below the threshold at which SLSWA is required to enact immediate responses such as a beach closure when the shark is within 1km of the coast.

More sharks were also seen closer to shore — within 200m of the beach — although this is believed to be correlated to the flight paths taken by the patrol helicopters.

SLSWA general manager Chris Peck said the figures highlighted the value of the aerial patrol program in monitoring popular stretches of coast for sharks.

He said the number of actions taken in response to sightings provided an important public safety service because it gave swimmers and ocean users peace of mind that they were being guarded.

Camera Icon Shark sightings at Swanbourne. Credit: SLSWA

“It does prove that the helicopter is a key part of the surveillance process,” Mr Peck said.

“There’s always noises out there and they tend to come from people who have got drones to sell that helicopters aren’t effective.

“But if you look at the difference in the sources and the detection methods, then helicopters are probably the most effective at this point in time.

“Helicopters play a really important role not only in spotting but also in the response.”