A shark attack on a surfer at Lighthouse Beach in NSW has prompted authorities to promise the installation of "eco-barriers" at the beach within months.

Local surfer Sam Morgan (20) became the ninth shark attack victim on the notorious stretch of the NSW north coast this year.

He was mauled on the leg by a bull shark at the beach in East Ballina on Tuesday and remains in a stable condition at Gold Coast University Hospital.

NSW Primary Industries Minister Niall Blair promised on Wednesday a mesh swimming enclosure would be installed with new technology to be trialled so the barrier nets don't capture sharks or other marine life.

Premier Mike Baird, however, says the nets haven't yet been built.

"We are in discussions with the manufacturer. We are trying to get them built and installed as quickly as we possibly can on the north coast," Mr Baird said.

Beaches in Ballina reopened on Wednesday night following a 24-hour closure from the time of the attack.