Skate and ray wings sourced from vulnerable species, DNA tests find

DNA testing by University of Salford researchers has found that supermarket skate and ray wings are being taken from declining species – despite being labelled as from more sustainable stocks.

In a blow to consumers who want to eat fish from sustainable sources, the most common species found on sale by Dr Andrew Griffiths from the School of Environment & Life Sciences was the blonde ray, which is bottom of the Marine Conservation Society’s sustainability rating.

Species sold as skate are difficult to identify as the body is cut from the fish before being sold to retailers.  However, using a technique known as DNA Barcoding, the researchers were able to quickly and cheaply pinpoint the identity of the fish.

One supermarket which had made a commitment to supplying more sustainable species and naming them on its packaging was in fact found to be mislabelling products and included sales of wings from the thornback ray, another declining species that can grow to over a meter in length.

Dr Griffiths believes that there is a fundamental problem facing consumers who want to promote sustainable fish. “Currently there is a dichotomy; the EU generally requires skates to be identified to the species level when landed, but this information is not being passed onto consumers,” he said. “This remains a real obstacle in allowing consumers to make informed choices.”

The study was part of a wider project from Salford and University College Dublin called Labelfish, which is looking at a large number of issues relating to the mislabelling of fish across the EU.

Earlier in the year, researchers working on the project discovered that 7% of the cod and haddock sold in Britain is actually a cheaper species. As well as tricking consumers, the practice of mislabelling fish can lead to less sustainable fish becoming overfished.

None of the skate species identified in the study were from species that are prohibited from being landed, but with three larger and therefore slower reproducing species including the blonde ray indentified, the results show that vulnerable species are amongst those being most exploited.

Dr Griffiths concluded: “This research and the wider Labelfish project show how difficult it remains for people to eat fish in a sustainable manner.  There is a lot of demand for accurate labelling and if suppliers can use DNA barcoding more extensively then both they, the public and the fish will benefit.”

Dr Griffiths’ study was originally published in the journal Peerj.

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