Fraudulent mislabelling of seafood is rampant in South Korea, where one-third of samples in a comprehensive DNA study were found to be mis-sold.

More than half of all sushi samples (53.9%) proved to be wrongly labelled, as did over one-third of fresh fish (38.9%) and sashimi (33.6%) samples, according to a report published this week by the Environmental Justice Foundation (EJF).

Not a single sample of Chinese white shrimp – also known as fleshy prawn – was the correct species, while nearly a third (27.8%) of all minke whale samples were in fact either dolphin, whose meat contains dangerously high mercury levels, or finless porpoise, a vulnerable species protected by Korean law.

The researchers took samples primarily in the capital, Seoul, where mislabelling was highest in restaurants and fish markets, as well as from online seafood purchases.

But the findings should not be seen as endemic to Seoul alone, said campaigner Hanmin Kim, who served as principal investigator on the study.

“Much of the seafood sold in Korea comes from Japan or China and in some cases there were species that we simply could not identify by DNA, so the number of [fraudulent] examples could actually be higher,” said Kim.

“In the provinces, many supermarkets and big superstores are less regulated and this is something that deserves more attention.”

The findings are likely to put further pressure on South Korea – which has one of the world’s highest rates of seafood consumption per capita – to dramatically improve its voluntary seafood traceability system, which campaigners have described as “woeful and pitiful”.

“These findings are shocking and speak to the failure of the Korean government to take this seriously. The Korean seafood traceability system has been in operation for 11 years but it has fewer than one-fifth of all operators signed up to it,” said EJF’s director, Steve Trent.

“If you have a product like fleshy prawn, where every single sample is mislabelled, how do you know that product hasn’t been fished without slave crews? How do you know where it was fished, how do you know if it’s gone through the necessary sanitary checks?”

Seafood fraud affects consumers’ health and their wallets, and also has an impact on the marine environment, as mislabelled seafood often comes from illegal, unreported and unregulated fishing.

Swordfish mislabelled as bluefin tuna can be sold for four to five times the price, while uncertainty over the origin and identity of seafood products raises concerns over food safety and hygiene, said Trent.

Overall, more than a third (105 out of 302) of all the seafood samples genetically analysed were mislabelled, the report found. The highest rates of mislabelling included Japanese eel (67.7%), mottled skate (53.3%) and common octopus (52.9%).

In recent years, stories about “seafood fraud” have increasingly made headlines in South Korea, where fears over imported products from China, as well as Japanese seafood affected by post-Fukushima radiation, have increased consumer awareness of the issue. But the government has not aligned its food safety programmes accordingly, says Kim.

“The government’s traceability system with agricultural meat like cows and pigs has nearly 100% coverage, but seafood traceability doesn’t even reach 20%: the government makes excuses that there are more species at sea, so traceability is more difficult,” said Kim.

“Just last year there was a huge scandal over halibut and mercury poisoning, and this year the government is launching a pilot project to make two species mandatory on the traceability system. But it’s not sufficient, and everyone knows it. The government has to show some will and expand the traceability coverage.”

For the study, EJF took 318 samples from 12 seafood groups over the course of a year, from January to December 2018. Most of the samples (45%) were purchased in restaurants; nearly a third (27%) came from major fish markets; and one-tenth (9.9%) were bought from superstores.

Almost all the samples were collected in Seoul, where half of national seafood consumption is concentrated, but samples of minke whale – which is mostly consumed in other provinces – were taken instead in Ulsan, Busan and Pohang.

An average of 25 samples were taken for each seafood group. The focus was on widely available groups that had been previously identified as prone to mislabelling by governmental authorities or media reports, as well as seafood that was possible to identify with DNA testing. All testing was carried out by the Korea Institute of Ocean Science and Technology, which was able to carry out successful testing on 302 of the 318 (95%) samples.

Mislabelling is likely to be lower in supermarkets than restaurants because the former have the capacity to invest in supply chain research and make changes at scale, said Trent.

“Restaurants are being duped. If you’re a restaurant on a Korean high street, you can’t do the due diligence required to investigate your entire seafood supply chain. That’s why you depend on your supplier to tell you if it’s clean or not,” said Trent.

“You need a traceability system that looks into the supply chain for you and ensures that products are legal, ethical and sustainable. Korea has highly sophisticated information technology and an expansive fish management team. But there’s a resistance to improving their traceability system and it’s just not good enough. They need to act now.”

EJF is calling on South Korea to adopt its 10 transparency principles as well as extend its catch documentation scheme to all seafood imports.