(CNN) - British fish and chip shops are selling endangered shark species under generic sales terms, a study from the University of Exeter has found.
Scientists tested the DNA of fish sold in restaurants and fishmongers under non-specific "umbrella" labels, and identified most of it as spiny dogfish, a species of shark classified by the International Union for Conservation of Nature as endangered in Europe and vulnerable worldwide.
The study, published in the journal Scientific Reports, concluded that generic names permitted by the EU like rock, rock salmon, huss and flake were often applied to meat from endangered sharks.
Although the EU prohibited the fishing of spiny dogfish (or Squalus acanthias) in its waters in 2011, fisheries in the US and Canada in particular continue to export catches to the UK.
Shark fins sold by British wholesalers were also derived from threatened species, the study found -- including the scalloped hammerhead shark, which the IUCN classifies as globally endangered. Other species discovered included the shortfin mako and the smalleye hammerhead, both of which are considered vulnerable.
Senior author Andrew Griffiths, a lecturer in biological science at the University of Exeter, told CNN that sharks are particularly at risk of population decline thanks to their slow rate of reproduction. "Sharks typically take a long time to reach sexual maturity and, once they do, produce relatively few young -- at least in comparison to most fish that are commercially caught.
"This makes them very vulnerable to overfishing as they simply cannot replace themselves very quickly," he said.
The researchers tested 117 tissue samples from 90 different retailers in the UK: 78 from fish and chip shops, which were battered and fried when collected, and 39 from fishmongers, which were either fresh or frozen. They also bought 10 "dried, skinned and bleached" shark fins from UK wholesalers, and obtained a further 30 from the UK Customs Agency. These were seized at the UK border, originating in Mozambique and en route to Asia.
Researchers determined the species to which the samples belonged by cross-referencing the DNA sequence of a sample with the Barcode of Life DNA database. The species identified included the starry smoothound, nursehound, Pacific spiny dogfish and blue shark.
Most common, however, was the spiny dogfish, which 77 of the samples were found to be.
Cathy Hobbs, the study's first author, told CNN: "The issue with shark meat products in the UK is that many species fall under umbrella labels when being sold. In other European countries, labeling requirements are much more specific allowing more consumer confidence. We should adopt more precise labeling here in the UK.
"Until labeling becomes more specific, it's difficult to know what you are purchasing," Hobbs said.
According to Ali Hood, director of conservation at the Shark Trust, the team at the British charity "weren't surprised" by the study's findings. "Globally, sharks and rays are at a substantially higher risk of extinction than most other groups of vertebrates," she told CNN.
Consumers concerned about buying endangered shark meat should ensure they ask questions about their seafood's provenance, Hood advised. "Many retailers pride themselves on their sourcing, so hold them to account." And if a shop or restaurant can't prove where their fish comes from? "Make an alternative choice," she said.
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