An unknown percentage of the fish we eat isn't what's it's purported to be, according to the UN's Food and Agriculture Organisation (FAO), which recently held a meeting to explore how forensic techniques could help address the problem.

The first victim was a Caucasian male in his late 30s. He popped down to the pub for lunch and ordered fish and chips. As he enjoyed his meal alongside a pint, he thought to himself that he'd never tasted haddock so fresh. But he was wrong. What he was eating wasn't haddock at all. The second victim was a young Japanese woman in her early twenties. On a business trip to the US, she ordered tuna sashimi for lunch. It seemed fishy to her—and she was dead right. The third was a South African fisherman we'll call "Nate." He never ate a thing, but as he plied the waters of the new fishery he'd recently started working, elsewhere poachers harvested protected spiny lobster and exported them with false documents—further damaging recovering fishing grounds Nate hoped to one day fish again.

Seafood identity theft? In each of these three hypothetical cases the culprit was mistaken or misrepresented identity—of seafood.

"Identifying unprocessed fish is usually fairly easy," says Michele Kuruc of FAO's Fisheries and Aquaculture Department. "But today seafood is transported far abroad, to places where it may not be well known. Plus, as the industry has globalized, it is common that fish products are processed on floating factories before they come to shore. What inspectors see often doesn't look much like a fish in the wild."

In some instances, accurately identifying fish may be beyond the abilities of inspectors. Innocent clerical errors can end up turning one type of fish into another.

Or unscrupulous fishers and traders game the system to avoid restrictions or taxes.

According to Kuruc, those involved in illegal, unreported and unregulated (IUU) fishing use many methods to conceal their illegal activities and get their ill-gotten goods to market. "Fraudulent product substitution and use of false labels and documentation are frequently employed to transport and market products illicitly," she says.

The result? An unknown percentage of seafood on the shelves simply isn't what's it's purported to be.

Big stakes: This is a problem. Today's more conscious consumers are aware of the multiple health benefits of eating seafood—but are also keen to be sure they're eating fish that has been caught or farmed responsibly and is safe to eat.

And there's much more at stake.

In recent years a number of major food retailers have committed to stocking only seafood certified as sustainable. As of January 1, 2010, the world's biggest seafood market, the European Union, has put in place regulations aimed at blocking imports of fish not harvested legally.

With 110 million tonnes of seafood consumed globally per year, international trade in fish is valued at a record high of $86 billion annually and is a major source of employment and government revenue for developing countries, where many of the fishing grounds that feed the first world are found.

Additionally, concerns about the wellbeing of many fish stocks necessitates diligent oversight of what fish are being taken and where.

Forensic science can help

Forensic technologies based on genetics and chemistry are already being used by some countries to monitor and control trade in produce, animals and timber. So FAO recently convened a workshop of experts, inspectors, law enforcement officials, scientists and academics to discuss how they might be more widely deployed in fisheries enforcement.

"We're interested in promoting wider use of available forensic techniques, in particular by developing countries," Kuruc says. "Some countries have successfully used various forensic methods in investigations and court cases, but many fisheries monitoring, control and surveillance personnel still remain unaware of their existence."

DNA analysis can reveal the species of a suspect white fillet. Chemical tests on fish earbones reveal absorbed nutrients and pinpoint the region where they were caught.

"We need to push the envelope, because we can be sure that those involved in IUU fishing are doing so," Kuruc added. "One workshop participant related how a group convicted of illegally trading abalone confessed that they learned techniques for destroying evidence by watching CSI: Miami."

In addition to surveying the state of the art and brainstorming how forensics might be used in fisheries and identifying needs—especially for capacity building in developing countries—the meeting also looked at best practices in handling evidence, how inspectors should be trained, and identifying laboratories capable of handling testing. (In many cases, labs in developing countries currently testing for food quality could be upgraded to conduct forensic work.)

The group also agreed to operate as an ad hoc FAO reference network that can be tapped by authorities around the world for guidance and advice.

"Fish can be properly identified if samples are handled properly, get to the right labs, and checked using forensic techniques," said Kuruc. "So the idea is to help countries that don't have such facilities and know-how access so them, so they can identify and prosecute cases of malfeasance."