Installing shark warning signs at Oamaru Harbour "might be an overreaction", Waitaki District Council chief executive Alex Parmley says. 

Police approached the council about putting up signs in the harbour area after Alvira Repia-King, 13, was bitten by a shark a week ago near Holmes Wharf, and needed 52 stitches. 

The shark, described by witnesses as dark grey and about 1.8m long, was believed to be a sevengill. 

Parmley said while the council had not ruled out putting up warning signs, he was not convinced they would prevent future incidents. 

The attack was an "extremely rare incident, not just for Oamaru but for New Zealand overall". 

"At this stage, we're not sure putting signs up would have prevented that incident happening." 

Alvira Repia-King was attacked by a shark at Friendly Bay on Sunday afternoon. Photo / Supplied 

For now, the council was directing people to existing advice about swimming in open water, and discouraging people from dumping fish waste at the harbour, after reports that had been occurring close to where the attack happened. 

New Zealand Marine Studies Centre educator Rob Lewis said in southern New Zealand, sevengill sharks often moved closer to shore in summer and were regular visitors to Holmes Wharf area. 

They were "very curious animals", and fast movements and splashing could could trigger a shark to investigate. 

But people should not be scared of swimming at Oamaru Harbour, he said. 

If approached by a sevengill shark, the most important thing to do was keep eye contact with it, "after which, you should try, as calmly as possible, to exit the water".