Consumer, beware: When you're buying fish, you may not get what you pay for.

In a cross-Canada investigation, fish sold as wild Pacific salmon turned out to be farmed Atlantic salmon. Sea bass was actually endangered Patagonian toothfish, marketed as Chilean sea bass, which is a different species. Cheaper skipjack was substituted for sushi grade tuna.

Tilapia stood in for snapper and even white tuna. "Bluefish" from a Chinatown shop turned out to be a species of herring that's not even listed in the official database of the Canadian Food Inspection Agency.

About a quarter of 500 fish samples turned out to be misidentified or mislabelled. They were genetically tested and matched using the world-famous Barcode of Life DNA database at the Biodiversity Institute of Ontario, University of Guelph.

The results are in line with previous, smaller studies, says Robert Hanner, global campaign coordinator of a Barcode of Life (BOL) project to identify genetically all the fish in the world, called FISH-BOL.

"Yes, we continue to see things that look fishy," says Hanner, an assistant professor at the University of Guelph. "It's a problem across Canada. It's a problem across markets."

Hanner is expected to unveil the findings Wednesday at the third international BOL conference in Mexico City. He gave the Star a briefing in advance.

The fish samples were collected during 2008 and 2009 from supermarkets, fishmongers, restaurants and even frozen food boxes. The investigation was conducted in conjunction with Bioscience Education Canada, with help from the Ontario Genomics Institute. Both are based in Toronto.

To collect the fish, 166 high school and college students were recruited in Toronto, Riverview (N.B.), Halifax, Kanata (an Ottawa suburb), Guelph, Saskatoon, Edmonton, Spruce Grove (an Edmonton suburb) and Richmond (B.C.). The Toronto contingent included gifted students in the science club at Northern Secondary School and students in the computer bioinformatics program at Seneca College.

It was more of an educational exercise than a scientifically rigorous study because background information and collection methods were "spotty," Hanner cautions. "This is an investigative report, not a scientific study."

However, he says, the results do put the spotlight on a widespread problem. Implications of misidentified fish include consumer fraud, food safety issues and ecological concerns.

In most cases, Hanner says, cheaper fish are being substituted for pricier species. "The bottom line is that there is a lot of market fraud."

Food safety concerns range from the fear of unsuspectingly being sold goods from a polluted Asian fish farm to the fear of unknowingly biting into a fish one is allergic to. The fear of ending up with a poisonous fish in your soup is not far-fetched, either. That happened three years ago. An investigation was launched in three U.S. states after a few consumers fell ill. They had bought what was marketed as headless, gutted monkfish from China. Barcode of Life testing proved it was puffer fish, or fugu, which contains a neurological toxin that can cause respiratory paralysis and even death.

Mislabelling and misidentification in the marketplace is a sign of overfishing, Hanner says. He points out that trawlers "hammer" fish stocks, then move to new areas where they land similar but different species. With 90 per cent of fish stocks in trouble, Hanner says, accurate tracking of species being caught and sold is crucial. A diner, however, is not likely to be able to tell the difference.

Shauna MacKinnon of the Living Oceans Society says misidentification of fish is "a huge problem" because it undermines the efforts of conscientious consumers and buyers.

"If you're a supermarket or a chef, you might be trying to make a sustainable choice," she says. "When there's so much mislabelling or misidentification, you can't be sure."

For example, Chinese tilapia is considered a poor choice because of concerns about chemical use in vast fish farms. MacKinnon says it is substituted for U.S. tilapia, which is farmed with more concern for the environment.

Hanner says tilapia, a freshwater fish, is the most common stand-in for other, more expensive fish. The most misidentified fish remains red snapper, an endangered ocean fish.

Earlier this year, a Toronto Star investigation revealed widespread substitution of tilapia for the promised snapper at Toronto sushi restaurants. Of samples collected from 12 restaurants across the city, 10 were actually tilapia.

In Guelph's cross-Canada investigation, tilapia was sold as white tuna, as well as snapper. Catfish was replaced by inferior Asian basa; this is officially allowed in Canada but not the United States. And even though 7,175 fish species have been genetically bar-coded, one sample sold as sea bass didn't match anything in what Hanner calls "the most comprehensive database that has ever been constructed."

About 100 main market species end up on our dinner plates. Types of fish collected by the students included halibut, turbot, cod, Caspian loach, dried capelin, butterfish, corvina, mackerel, pike, monkfish, Alaskan black cod, blackjack, swordfish and mahi mahi.

There are an estimated 31,300 fish species on the planet, which in turn have 279,500 names. Monikers include scientific names, common names, marketing names and cultural names. Fish are even renamed for better PR (would you rather eat slimehead or orange roughy?). The Canadian Food Inspection Agency maintains a list of "acceptable common names" for seafood.

Like the miracle of the loaves and fishes, the list of seafood names keeps growing – and so does consumer confusion. "It keeps expanding, with more names, and more and more ambiguity," Hanner says.

What is a poor consumer to do?

Richard Fung, a Toronto artist, writer and academic, eats fish about four times a week.

Recently, he swears he has seen endangered Chilean sea bass "under strangely new fish names," and has been perturbed by the sale of basa identified on separate occasions as turbot and sole.

"I'm suspicious of a lot of fish sold as turbot in T.O.," Fung says in an email. "It's like sole – anything flat seems to be sold as sole."

Nowadays, Fung puts suspicion on his shopping list. "I find fish labelling vague everywhere and I never know if to trust it, not just species but when a shop says `wild salmon,' for example," he says. "I would like to see provenance and price listed with fish."

That's what they are doing in Europe. MacKinnon says merchants there are required to provide a common name and country of origin, and to reveal whether fish is wild or farmed.

Canada is way behind, she says, with its poorly regulated seafood labelling and traceability. For instance, fish sticks that say "made in Canada" might only be breaded here, according to MacKinnon. The fish could come from three different countries.

"Seafood, more than many other products, has a long supply chain that can be very complicated," she says.

Conservationists have asked the government to take stricter action, MacKinnon says. "This is an ongoing discussion because Canada is behind other countries. The CFIA has been really unresponsive."

The agency, meanwhile, suggests that disgruntled fish buyers can email an area recall coordinator, at cfiamaster@inspection.gc.ca, or telephone the agency at 1-800-442-2342. At press time, it was formulating a response on questions of policy changes.

Amid a growing interest in what we are consuming and where it comes from, Hanner notes that initial anger over consumer fraud is shifting to dismay that the government is not protecting fish consumers.

"Translating basic research into public policy – I don't know how to do that," he says. "That's the missing link."

DNA bar-coding could help consumers, he says, but analysis time has to go from days to minutes, and the price has to drop from dollars to pennies. "The technology has got to become faster and cheaper," Hanner says.

Northern Secondary School science teacher Jane Lee says students who participated in the investigation were fascinated by the potential for Star Trek-style "tricorder technology" – a riff on Hanner's dream that DNA bar codes would one day shrink to the size of hand-held devices.

"That puts the power into the hands of anyone who has the device," says student Eric Yam.

In the meantime, Hanner suggests buying whole fish instead of fillets, which are harder to identify on the plate.

Fish caught by Canadian trawlers in Canadian waters are more "likely to be accurately labelled," he adds. Better still, try fish caught nearby, such as pickerel plucked from Lake Erie.

"How do I avoid being duped?" Hanner asks. "Buy something local."