After the horse-meat scandal, experts believe that up to a quarter of cod samples in Dublin have been mislabelled.
Irish people are eating more fish. It's healthy, light in calories, but new research shows we could be eating cheap fish substituted for more expensive species. A recent survey in Europe showed about a quarter to a third of fish products tested were not what was described on the packet or menu.
More worrying is that new species of fish, some which have never been consumed before, are being sold into the fish pies, fish cakes and even fresh fish that we buy.
We know from the shocking Food Safety Authority of Ireland's study in 2011 that up to a quarter of cod samples bought in Dublin restaurants, shops and supermarkets were, in fact, cheaper species.
In the case of smoked cod, nearly 90pc was a different fish.
We may think that most fish on our plate originates off a boat but in fact much of the fish sold in Europe enters through Frankfurt airport with vast amounts of farmed fish now arriving from Vietnam and China.
Testing at the Eurofins laboratory in Hamburg has found types of fish entering Europe that have never seen in the food chain before.
Biologist Dr Stefano Mariani recently DNA tested cod sold in Ireland and Britain, finding again that up to 7pc of fish sold in the UK is mislabelled.
Cod can be substituted with cheaper fish like pollock and Vietnamese pangasius, which is farmed in estuaries in South-East Asia.
Dr Mariani said: "Consumers should be able to go to a shop and know they are eating what they paid for."
The lobbying group Oceana, which campaigns for tighter controls on fishing, said the global fish industry was "murky and complex".
Oceana's tests on fish sold in the US found that 25pc of the fish served in restaurants in New York was not what it was said to be on the menu.
The problem of mislabelling is so big that the EU is to fund a project named 'Labelfish' to DNA test exactly what is being sold to consumers across Ireland, the UK and Europe.
Dr Mariani believes that the patterns of fish substitution he noticed in Ireland and the UK point towards food fraud.
"We noted that there were some suppliers that were consistently handling fish that was proven to be mislabelled, which suggests that a lot of mislabelling occurs before the fish gets delivered to the supermarket," he said.
He wants tougher regulation and more effective labelling, so that fish can be sourced and traced. Chinese tilapia and pangasius – a type of Asian catfish – has been found to be sold as monkfish and cod. Pangasius is also sometimes sold in Ireland as 'river cobbler'.
The EU has asked for increased food safety standards from Chinese and Vietnamese fish farms but some campaigners believe pangasius is farmed in unhealthy conditions.
The World Wildlife Fund says: "Farms are sometimes constructed and/or operated outside the legal framework for addressing environmental, social and food safety issues."
In 2011, Asda and Morrisons withdrew pangasius from their shelves after internal testing found "issues with the quality of the fish".
Recent research from Bord Bia shows that Irish consumers want to eat more fish but a quarter of respondents (25pc) said they lack confidence when cooking fish.