A man has been left with a gashed leg and beaches have been closed after a shark attack on the NSW north coast.

The 42-year-old local was bitten at Shelly Beach, near Ballina, at about 7.10am Wednesday.

He is believed to have fought the shark off with his surfboard and was able to paddle to shore.

The man, who sustained a 20 cm gash, took himself to Ballina Hospital and has since been transferred to Lismore Base Hospital.

Jimmy Keogh, the Surf Lifesaving duty officer in the region, said beaches in the area would be closed for 24 hours, at the request of police.

“You are looking at all the beaches from South Ballina beach through to Lennox Head, so we are just advising people to follow directions by lifeguards and lifesavers and police on the beach,” Mr Keogh said.

Ballina Mayor David Wright, speaking from Shelly Beach, described the attack as “just one of those” and urge people to take care in the water.

“He [the shark] grabbed him on the leg and pulled him off the board. He used the board to belt the shark away,” Mr Wright told Sydney’s 2GB radio.

“He came onshore, wrapped his leg up and went to Ballina Hospital. He’s now been transferred to Lismore Hospital. He’s got an eight inch (20cm) cut on his calf.”

The attack comes little more than a day after 33-year-old Melbourne doctor Daniel Christidis died from “horrific” injuries suffered in a shark attack at Cid Harbour in far north Queensland.

Dr Christidis died Monday night after being attacked while stand-up paddle boarding during a holiday with nine other friends on the popular Whitsundays.

The deadly attack occurred just two months after a woman, 46, and girl, 12, were critically injured in separate attacks on consecutive days in the same body of water.

Temporary signs warning people not to swim at Cid Harbour will be erected by the weekend and Queensland Fisheries Minister Mark Furner said permanent signs will be in place within the next few weeks.

“We can’t be clearer – don’t swim in Cid Harbour,” Mr Furner said.

-with AAP