Researchers tested DNA from tissue samples collected from fish-and-chip shops and fishmongers in the U.K. and found that majority originated from the threatened spiny dogfish (Squalus acanthias), frequently sold under generic names like rock, huss, and rock salmon.

The study also analyzed shark fins from wholesalers in the U.K., and found that many of them had come from the endangered scalloped hammerhead shark.

Seafood should come with accurate, complete species information for consumers to make informed choices, the researchers write, instead of ambiguous, “umbrella” terms that cover multiple species.

Threatened species of sharks are being sold under generic terms in fish-and-chip shops and at fishmongers in the U.K., a new study has found.

For consumers, shark products and species can be hard to identify: any distinguishing features are usually removed before shark steaks are sold; shark meat is battered and fried in traditional fish and chips; and dried shark fins are typically bleached and trimmed, complicating identification.

To counter this problem, researchers turned to DNA testing of shark products. They analyzed 78 tissue samples collected from fish-and-chip shops, and 39 samples collected from fishmongers, mostly in southern England. They found that the majority of the samples originated from the threatened spiny dogfish (Squalus acanthias), frequently sold under generic names like rock, huss, and rock salmon.

The spiny dogfish, listed as a species vulnerable to extinction on the IUCN Red List, has been declining globally, mainly due to overexploitation by fisheries. In the northeast Atlantic, where populations of the species have plummeted by 95 percent, the species is considered critically endangered and commercial targeting of the shark in the region is banned by the European Union.

Selling spiny dogfish under generic terms raises ethical questions, the researchers say in the study published in Scientific Reports. The shark meat in the fish-and-chip takeaway could have originated from well-managed stocks, where population trends are more positive. But it could also have come from a place where the shark’s population is either threatened or where its exploitation remains unregulated.

“It’s almost impossible for consumers to know what they are buying,” lead author Catherine Hobbs, a master’s student at the University of Exeter, U.K., said in a statement. “People might think they’re getting a sustainably sourced product when they’re actually buying a threatened species.”

Hobbs and her colleagues also analyzed DNA from shark fins collected both from wholesalers in the U.K., where the fins were destined for Asian markets, as well as fins seized by the U.K. customs office. They found that most of the fins had been sourced from four shark species, including the scalloped hammerhead (Sphyrna lewini), an endangered species, and the shortfin mako (Isurus oxyrinchus) and smalleye hammerhead (Sphyrna tudes), both listed as vulnerable. The scalloped hammerhead is listed in Appendix II of the Convention on International Trade in Endangered Species of Fauna and Flora (CITES), which means that the international trade in the species must be highly regulated and not be detrimental to populations in the wild.

“The discovery of endangered hammerhead sharks highlights how widespread the sale of declining species really is — even reaching Europe and the U.K.,” said co-author Andrew Griffiths, a lecturer at the University of Exeter. “Scalloped hammerhead can be imported under strict conditions, but the wholesaler had no idea what species the fin belonged to.”

For consumers to be able to make informed choices, seafood should come with accurate, complete species information, the researchers write, instead of “umbrella” terms that cover multiple species.

“The use of such ambiguous labels makes it extremely difficult for consumers to exercise a right to avoid species of higher conservation concern or those associated with specific health issues [arising from allergens or toxins like mercury],” they write.

Hobbs added that knowing which shark species were being consumed in the U.K. would also help address the decline in shark populations.

Citation:

Hobbs, C. A., Potts, R. W., Walsh, M. B., Usher, J., & Griffiths, A. M. (2019). Using DNA Barcoding to Investigate Patterns of Species Utilisation in UK Shark Products Reveals Threatened Species on Sale. Scientific Reports, 9(1), 1028.