Customers take sushi of a bluefin tuna which was bought by sushi restauranteur Kiyoshi Kimura at the year’s celebratory first auction, at his restaurant near Tsukiji fish market in Tokyo. That’s according to new research out of the University of Michigan, which found that mercury levels in yellowfin tuna caught in the Pacific Ocean have increased nearly four percent every year since 1998. For seafood lovers, warnings of high mercury concentrations in fish are not new.
The researchers looked at yellowfin tuna caught in the waters off Hawaii in three different years: 1971, 1998, and 2008. Drevnick said they made sure to compare fish based on their size, since they acquire more mercury from their environment as they age and grow.
They found that the mercury levels in tuna were very similar in 1971 and 1998, but increased between 1998 and 2008. But should you change your seafood diet in response? Possibly, according to the United States Environmental Protection Agency’s food consumption guidelines, which advise avoiding fish with mercury concentrations above .3 parts per million.
Drevnick said that in 1971 and 1998, yellowfin tuna had mercury concentrations below the EPA guideline. But the 2008 sampling came in at .336 ppm — above the EPA limit.
Yellowfin, also called ahi tuna, is popular in sushi and often sold as steaks. Small amounts of the fish are also mixed in with skipjack in canned light tuna.
In a separate study published last summer, researchers at Woods Hole Oceanographic Institution found that since the industrial revolution, mercury levels in the upper levels of the ocean have risen three-fold — a jump that isn’t reflected in yellowfin until very recently.
In the Woods Hole study, marine chemist Carl Lamborg said the mercury level increases expected over the next 50 years could add the same amount to the ocean that scientists observed over the past 150 years.
“The trouble is, we don’t know what it all means for fish and marine mammals,” Lamborg said in a statement. “It likely means some fish also contain at least three times more mercury than 150 years ago, but it could be more. The key is now we have some solid numbers on which to base continued work.” Read more…