A 2011 investigation by the Boston Globe reported that 48% of the fish it collected from Boston restaurants, grocery stores and seafood markets was sold with the wrong species name.

FDA spokesman Douglas Karas said the agency is working to determine how often, or at what point in the supply chain, fish substitution occurs.

Most of the seafood fraud complaints the FDA receives come from consumers at the retail level, Karas said.

The FDA is conducting a yearlong DNA test of about 800 fish collected across the nation.