Fish is mislabeled so that unhealthy fish sells as healthier types...or threatened fish species are sold under the name of a sustainable fish species. This means people trying to make purchasing choices based on their health or environmental concerns are not able to make accurate choices and fish sellers are profiting from trickery.
A group of 500 professional chefs has petitioned the federal government to enact stricter labeling rules so that they can actually buy the fish that they want. Apparently the free market needs a bit of regulation; consumer choice kinda fails to regulate things when people can't make accurate choices! Remember this, the next time someone tells you that government regulation hurts the "free" market.
These results were found by Oceana, an international ocean advocacy group, who tested fish in stores and restauraunts across the nation from 2010 to 2012.