(CBS News) After a report issued by an environmental group found that more than a third of the fish from over 1,200 samples taken from retail outlets across the U.S., Dr. Urvashi Rangan, the Director of Consumer Safety and Sustainability at Consumer Reports, spoke to "CBS This Morning" about the real danger behind mislabeled fish.
The "biggest offenders seem to be red snapper ... tuna, grouper," she said. "We found sole was also mislabeled."
Rangan explained that while "often times cheaper fish are being substituted and being sold as more expensive fish," the mislabeling can pose a health risk, too.
"Sometimes higher mercury fish are being substituted ... for tuna. An interesting fish called escalor -- which isn't even a tuna but an eel-like fish -- has an oil that can cause gastrointestinal distress can often be substituted," Rangan said.
She explained that the fish mislabeling issue is "pervasive and nationwide" and added that "it's happening at grocery stores ... [is] worse at restaurants, and sushi bars seem to be the worst of all."
One issue could be the "many steps to the chain," because 84 percent of fish in the U.S. is imported.
"[There are] many steps to getting here, distribution ... the tracking systems are not very good," Rangan said. "The FDA is now stepping up surveillance based on DNA testing, not just looking and hopefully once that gets into place, we're going to have some better tracking systems.