Artful, healthy and delicious, sushi in Montreal has transformed itself from traditional Japanese delicacy to a fast-food treat in a matter of years.

White rice, a few pieces of raw fish, some soy sauce - the results are mouthwatering, and many Montrealers are willing to pay a premium to enjoy them. But are restaurants using a bait and switch?

CTV Montreal decided to find out.

After gathering 48 samples of fish - three samples each from 16 restaurants - they were sent to a laboratory in Guelph, Ont, to be tested.

The samples were randomly selected: Restaurants ranged from fast-food eateries to upscale establishments throughout the city and at each, we selected a variety of products from their menu.

The test was accurate: A team of scientists from the Biodiversity Institute of Ontario at the University of Guelph used a revolutionary method of DNA barcode sequencing to determine the precise species of fish, a tool both identifying known species and discovering new ones.

The results were astounding.

Of the 48 samples tested, 20 were mislabelled and 5 were undetermined, meaning at least 45 per cent of the fish was not what customers were paying for. Fourteen of the 16 restaurants mislabeled at least one of the products they sold us.

"Their sequences are radically divergent. They're not even close," said Robert Hanner, associate director of the Canadian Barcode of Life Network at the Biodiversity Institute.

Yellowfin tuna was replaced with less expensive blackfin tuna. Flying fish caviar was substituted with a cheaper capelin roe.

But the biggest culprit? Red snapper. Of the 12 samples we tested, every one of them was, in fact, one of the cheapest fish available: Tilapia.

CTV returned to some of the restaurants to demand some answers.

One sushi chef who preferred not to be named claimed that in certain parts of Japan, tilapia was interchangeable with red snapper.

"Tilapia is different in different states. They have different colours and tastes," he said, adding that he thought red snapper was a type of tilapia.

The difference, however, is vast.

Fished from the wild, usually in the Gulf of Mexico, red snapper sells for about $12 per kilogram in Montreal.

Tilapia is mostly farmed, and costs just $2 per kilogram.

Beyond the price difference, local fishmongers say the quality of tilapia simply isn't fit for sushi.

Sushi restaurant owner Soly Vaar readily admitted to substituting tilapia for red snapper, claiming it's less expensive and has a longer shelf life. They receive their tilapia in frozen, vacuum-sealed packages.

"For the tilapia, it's almost the same fish. It's the same taste and everything, and we can keep longer. And we receive everything already in the bags," said Vaar.

"It's almost all the Japanese restaurants in Montreal that use tilapia," he said.

Montreal's food inspection department says advertising one product and selling another is against provincial law.

"It is not acceptable that misleading information is given the customer," said Myrto Mantzavrakos of the Montreal Food Inspection Division.

Still, Matzavrakos admits that because of a lack of resources, city inspectors tend to focus only on violations that could harm consumers, and eating raw tilapia isn't dangerous.

In the end, it's up to restaurant owners to decide if this is ethical business - and it's up to consumers to sniff out a raw deal.