The mainstream media had this idea first, they picked up the story of the New York highschool student who tested Red Snapper in various sushi restaurants and found that it was often Talapia.

That story got repeated in some jurisdictions, now a year or so later someone gets around to doing it with vegan food.

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EDIT:

Sushi from New York: http://www.nytimes.com/2008/08/22/science/22fish.html?scp=3&...

Sushi from Toronto (reported in Vancouver): http://www2.canada.com/vancouversun/news/story.html?id=4381b...