Listening stations that monitor the movement of sharks and tweet warnings to beachgoers are to be dropped into waters off the New South Wales south coast in an effort to prevent attacks.

The State Government announced a $16 million shark mitigation program last year and a number of the satellite-linked stations were installed at locations on the state's north coast.

Primary Industries Minister Niall Blair said the technology would now be rolled out at Kiama, Sussex Inlet, Mollymook, Batemans Bay and Merimbula.

He said the listening stations would be set up in time for the summer.

"They are there to detect our tagged sharks and send the information when these sharks swim past these listening devices back through our Shark Smart app, but also Twitter, to alert that they're there," he said.

"That means we can have a more informed beach-going public to help them reduce the risk when it comes to interaction with sharks."

The listening stations detect a tagged shark that swims within 500 metres of a device, which is attached to a buoy.

An alert is then sent to a base station over the 4G network, and the message is relayed to the NSW Government's Shark Smart app and Twitter account @NSWSharkSmart.

Mr Blair said 29 great white sharks and 88 bull sharks had been tagged in a collaborative effort between the Department of Primary Industries and the CSIRO.

"Our devices will also pick up any sharks that have been tagged in other waters," Mr Blair said.

"We're also looking at other types of technology that don't rely solely on tags and use other things like sonar to try and identify those sharks."

In March, a 22-year-old surfer sustained a serious injury to his thigh when he was attacked by a shark at Kiama, on the north end of Bombo Beach.

Ten listening stations are already in place between Tweed and Forster, with more set to be deployed at Crescent Head, Old Bar, Hawks Nest, Redhead and Bondi.

Better system needed to warn surfers: Ballina mayor

But Ballina's mayor said a close call involving two teenagers yesterday afternoon highlighted the shortcomings of shark listening stations.

Two surfers were knocked from their boards by a large shark near a listening station at Sharpes Beach on the NSW north coast.

Mayor David Wright said even if the shark had been tagged and picked up by the buoys, the surfers may not necessarily have been alerted about the shark's location.

"We still don't have a mechanism to put that message out to everybody," he said.

Mr Wright said the system should be able to alert surfers in the water when a tagged shark was detected.

"I've still been negotiating with DPI (Department of Primary Industry) to get sirens on the headlands, [to] maybe have flashing lights," he said.

"That would give the surfers an idea that there had been sharks spotted."