Mercury is higher in some tuna species

NEW YORK, April 22 (UPI) -- Mercury levels differ among some species of tuna than others, U.S. researchers found.

Researchers combined DNA barcoding used at the American Museum of Natural History with analysis of mercury content at Rutgers University and found tuna sushi purchased in supermarkets -- yellowfin tuna -- might have less mercury than that from restaurants.

Sushi samples were taken from 54 restaurants and 15 supermarkets in New York, New Jersey and Colorado, and all of were identified with DNA barcoding as either bigeye tuna, yellowfin tuna or bluefin tuna species.

The samples were all tested for relative mercury content.

"We found that mercury levels are linked to specific species," Jacob Lowenstein, a graduate student affiliated with the museum, said in a statement. "So far, the (United States) does not require restaurants and merchants to clarify what species they are selling or trading, but species names and clearer labeling would allow consumers to exercise greater control over the level of mercury they imbibe."

The findings are published online in Biology Letters.

However, some say research also points to fish, which contain omega-3 fatty acids -- even with traces of mercury -- may enhance heart and brain health.

"Our study in the Seychelles suggest the nutrient benefits of fish equal or exceed any theoretical adverse effects from methyl mercury in fish," Dr. Gary Myers, a professor of neurology and pediatrics at the University of Rochester Medical Center in New York told United Press International.