Grey nurse blamed for WA shark attack

A grey nurse shark was probably responsible for biting 18-year-old Eli Zawadzki on the foot in waters south of Perth, the Department of Fisheries says.

Shark tooth fragments collected from inside Mr Zawadzki's foot have been identified as belonging to the protected and usually placid species, according to spokesman Tony Cappelluti.

"We gathered some evidence yesterday after the incident and it's our opinion that it's in all likelihood a grey nurse shark that has been involved," Mr Cappelluti said.

He said the bite was most likely prompted by an accidental encounter between Mr Zawadzki and the fish, "like the surfer has run into the shark".

"That's normally how grey nurse sharks get involved in an incident," Mr Cappelluti said.

Mr Cappelluti said the victim was about 40 metres offshore while surfing at Pyramids Beach in Dawesville on Wednesday afternoon when he felt the bite on his foot, before turning around and seeing a head.

"He didn't think it was a very large shark," Mr Cappelluti said.

The beach remains closed but authorities have ruled out any attempt to capture the animal responsible.

A Department of Fisheries spokeswoman said there had been no shark sightings in the vicinity since late on Wednesday.

It's understood Mr Zawadzki had surgery on Thursday.