A seafood fraud investigation DNA tested fish sold in the US. Here’s what they found

Here’s a fishy riddle. Question: when is a sea bass not a sea bass? Answer: when it’s a giant perch. That’s the conclusion of a recent study on fish sold to consumers in the United States, which found that 20% of the samples tested were mislabelled.

The study, by Oceana, a US non-profit dedicated to protecting the world’s oceans, sampled 449 fish purchased from shops and restaurants in 24 US states and the District of Columbia. DNA testing was used to establish the true identity of the samples.

One-third of all shops and restaurants checked sold mislabelled seafood. Fish was most often misdescribed on restaurant menus (26%) and at smaller markets (24%). An eighth (12%) of samples from supermarkets was found to be mislabelled.

The most commonly mislabelled species were sea bass (55%) and snapper (42%).

Fish fraud is a global problem

The study also found imported seafood was sometimes marketed as locally-caught, while vulnerable species like the Atlantic halibut were falsely advertised as a more sustainable catch. For example, two outlets in Florida had substituted an Indian Ocean grouper for local delicacy hogfish.

“In cases like these, consumers think they are buying a local fish fresh off the boat, but what they actually receive is something that was imported and sometimes farmed,” the study notes.

Oceana says fish fraud is a worldwide problem, covering up illegal fishing and misleading customers trying to buy sustainable seafood. Illegal fishing refers to any fishing that takes place against national laws or international obligations, against conservation or other stock-management measures or without other authorization. It can deplete fish stocks, put those fishing illegally at an unfair advantage and damage marine habitats.

Digital data

The World Economic Forum, in a White Paper published earlier this year, called for renewed action to stamp out illegal fishing, which it said accounted for a third of the fish taken from the oceans at an annual cost to the global economy of up to $23.5 billion.

The Forum urged nations to work together regionally and to use digital data-sharing technology to trace the source of fish that comes into ports worldwide. In particular, it called for investment in digital catch-monitoring to replace the current largely paper-based systems.

Oceana called on the US government to tighten regulations on the import and sale of fish to allow it to be tracked from boat to plate. It warns that, at present, it is impossible to see who in the supply chain is falsifying the description of a fish shipment.

Tough policies to combat fish fraud introduced by the European Union led to an almost immediate reduction in fish mislabelling.