Mislabelling of fish common in Italy, says DNA study

Just over a third of seafood products sampled in an Italian study have been found to contain species not indicated on the label.

Researchers from the University of Catania in Italy took 54 samples of 20 different white fish products sold at markets and used DNA barcoding to identify the species present, including frozen breaded steaks and fish fingers. Mis-labelling was evident on 35 per cent of the products.

The study focused on European hake (Merluccius merluccius) species that are they scientists say are "often subject to fraudulent substitution due to their high commercial interest" and has been in short supply as a result of over-fishing over the last five years. It also included cod and other species including Atlantic Pollock.

Using molecular biology tools to examine the DNA sequences of fish in the products, focusing on cytochrome oxidase I (COI) gene which can be used as a genetic barcode to discriminate between 98 per cent of animal species.

The identification of fish is mandatory in the EU and laws require that fish labels indicate the complete scientific and commercial name of the species without inducing errors. Studies have estimated that the proportion of mis-description is 30 per cent, and typically more common in restaurants and takeaways than supermarkets and other shops.

"Based on the Italian decree the fish products labelled as hake must contain the species M merluccius," write the authors in the journal Food Control. Other Italian studies have found similar findings, they note, although one involving more than 100 breaded fish samples found no evidence of substitution.

"Mis-labelling percentages are very high and call for strategies to ensure product authenticity of this high value meat," they conclude.

The use of COI as a DNA barcode for species identification has already been adopted in the US, Brazil, and Canada and could be beneficial in European markets, including Italy.

It may also be suitable for automation on a portable device, which would make it easier to monitor supply chains in the field. Other marker sequences, including cytochrome b (cytb), have also shown promise for seafood identification.

Other research groups have taken different approaches to try to tackle mis-labelling of fish products. A team from Spain, Norway and Iceland are developing a database of hundreds of samples from across Europe - with the help of the general public. While still at the sampling stage, the citizen science project will eventually use genetic profiling to determine the level of mis-description.