Fish and chip shop owners in Norfolk have said reports an endangered species of shark is being sold around the UK could affect their trade.

Scientists at the University of Exeter used DNA barcoding to identify species of fish on sale at chip shops and fishmongers .

And results revealed fish sold under the names huss, rock, flake and rock salmon were actually a shark species called spiny dogfish, classed as endangered in Europe.

Chef and restaurant owner Galton Blackiston said he believed the sale of the shark was due to 'ignorance' from shop owners.

Mr Blackiston, who owns the fish and chip shop No 1 in Cromer, said: 'It used to be popular but I haven't seen it for a long time.'

And the restauranteur said no rock was sold at No 1, or Upstairs.

He said: 'I would be very upset if it was. I should think this is borne of ignorance by the shops.

'As far as we're aware, rock is dogfish and I certainly wouldn't serve an endangered species.'

He added: 'I think potentially there could be an impact on business but it is generally a niche product - 95pc of our customers get cod and chips and the rest is made up of haddock and plaice.'

Fishmonger John Lee, who also owns the Hot Rocks restaurant in Cromer, said: 'Rock salmon was always sold in fish and chip shops but they didn't want to put the word dogfish on the menu.

'None of the Cromer fishmongers sell that, as I don't think it's so popular nowadays.'

And Mr Lee said reports about the sale of spiny dogfish could cause problems for businesses.

He said: 'Trading is difficult enough as it is. It absolutely could be a worry.

'People need to research and understand the background of what they're talking about.'

He added: 'Everything we sell, you would have to do a lot of research to find out what they are and where they come from.'

Owner of Dave's Fish Bar in Sheringham, Jon Heathcate, said rock was on his menu.

He said: 'I've never heard it called an endangered species but I knew it was a type of shark and a lot of people think its an eel.

'If I did find out it was endangered species I would consider taking it off the menu.

'I don't sell many and it's not my bread and butter, so if it's that bad I'd take it off. We shouldn't sell anything that's endangered.'

Mr Heathcate added that the price of rock had increased significantly in recent years.