Tuna served in sushi bars should be labelled by species to allow eco-minded consumers to eat types that aren't endangered, says a Columbia University researcher.

Researcher Jacob Lowenstein made the recommendation after a study he led found that endangered bluefin tuna was routinely served at 30 sushi bars in New York City and one in Denver but wasn't always identified as bluefin.

Sixty-eight samples were collected for the research, which was published this month in the journal PLoS ONE. Of those, 22 were found to be bluefin tuna, but just eight were actually labelled as such.

The research team from New York-based Columbia University and the Sackler Institute for Comparative Genomics at the American Museum of Natural History found that almost half of the restaurants did not accurately label the kind of tuna sold, and only 14 of the samples used for this study were listed on the menu by a specific name like bigeye tuna, albacore or bluefin.

"When you eat sushi, you can unknowingly get a critically endangered species on your plate," said Lowenstein.

The U.S. Food and Drug Administration does not require tuna to be identified by type, making it "very difficult to get reliable information about the species you are eating," he said.

Lowenstein pointed out that an increasingly popular technique, DNA barcoding, is helping researchers see just what species are being consumed at sushi bars.

Five of the nine samples labeled in restaurants as "white tuna" were not albacore but rather escolar, a tuna that is banned for sale in Japan and Italy because it can cause gastrointestinal distress.

In mid-October, Monaco nominated northern bluefin tuna for a complete international trade ban to be considered when the Convention on International Trade in Endangered Species meets in March.