Sushi eaters do not necessarily know what they are biting into, according to researchers from the Sackler Institute for Comparative Genomics at the American Museum of Natural History. Researchers used DNA barcoding to determine the exact species used in tuna dishes from 31 different sushi restaurants in New York and Colorado. They determined that 22 of the 68 samples were bluefin tuna, an endangered species, although only eight of the samples were labeled as such by the restaurant. Five samples sold as white tuna turned out to be escolar, a fish banned in Japan and Italy because it causes stomach problems. The report further states that the rising demand for sushi is seriously threatening tuna species.