Putting up signs warning people about sharks in Oamaru Harbour ‘‘might be an overreaction’’, Waitaki District Council chief executive Alex Parmley says.

After an Oamaru teenager was attacked by a shark on Sunday afternoon, Oamaru police approached the Waitaki District Council about putting up warning signs in the harbour area.

Alvira Repia-King (13) received 52 stitches — 42 in her right arm and 10 in her back — after she was bitten by the shark while swimming near Holmes Wharf.

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

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

‘‘What happened the other day was a really unfortunate incident, and clearly we don’t want a repeat of that,’’ he said.

‘‘But it’s 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.’’

For now, the council was directing people to existing advice around swimming in open water.

There had been reports of people dumping fish waste into the water, close to where Sunday’s attack happened.

‘‘We don’t want people disposing of fish carcasses in and around the harbour,’’ Mr Parmley said.

‘‘It’s something they’re not meant to do.’’

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

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

‘‘Of course, their way of investigating is by biting things,’’ Mr Lewis said.

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

‘‘It’s awareness, and it’s just knowing what you’re getting yourself into.

‘‘[Sevengill sharks] have been around for a very long time, and the fact that we have so few negative interactions like this should speak to the fact that they’re not usually a problem.’’

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