Mercury levels in Hawaiian bigeye, yellowfin tuna rising

March 7, 2017 by Jim Erickson, University of Michigan
Bigeye tuna. Credit: Allen Shimada, NOAA NMFS OST

Mercury concentrations in Hawaiian-caught bigeye and yellowfin tuna are steadily rising and mirror increases in North Pacific waters that have been linked to atmospheric mercury emissions from Asia.

Researchers compiled and re-analyzed data from previously published reports on yellowfin and caught near Hawaii over the past four decades, then used a mathematical model to look for trends.

They found that mercury concentrations in increased about 5.5 percent per year between 1998 and 2008. Levels in bigeye increased about 3.9 percent per year from 2002 to 2008. Mercury concentrations tended to be greater in bigeye tuna than in yellowfin tuna.

The work was reported in a study scheduled for online publication March 6 in the journal Environmental Toxicology and Chemistry. The first author is Paul Drevnick, a former University of Michigan researcher who now works for the Alberta provincial government in Calgary. The other author is Barbara Brooks of the Hawaii Department of Health.

Most of the work was done while Drevnick was at U-M, and the research was funded in part by the university. The new study updates yellowfin findings that Drevnick reported two years ago and expands the effort to include bigeye tuna.

"This paper confirms our previous work showing that mercury concentrations in yellowfin tuna caught near Hawaii are increasing, and it demonstrates that the same phenomenon is happening in bigeye tuna," Drevnick said.

Both yellowfin and bigeye tuna are marketed as ahi and are widely used in raw dishes—especially sashimi—or for grilling. In January, the U.S. Food and Drug Administration and the U.S. Environmental Protection Agency added bigeye tuna to its list of fish to be avoided by pregnant women, women who might become pregnant, breastfeeding women and young children due to mercury concerns.

Mercury is a toxic trace metal that can accumulate to high concentrations in fish, posing a health risk to people who eat large, predatory marine fish such as swordfish and tuna. In the open ocean, the principal source of mercury is atmospheric deposition from human activities, especially emissions from coal-fired power plants and artisanal gold mines.

In North Atlantic waters, mercury concentrations peaked in the 1980s and '90s and are now declining in response to environmental regulations in North America and Europe.

But in the North Pacific, mercury concentrations in waters shallower than 1,000 meters increased about 3 percent per year between 1995 and 2006 and are expected to double by 2050 if current mercury deposition rates are maintained, according to Drevnick.

"The temporal trend in mercury concentrations in these waters is mirrored by the changes in mercury concentrations in yellowfin and bigeye tuna caught near Hawaii," Drevnick said. "For that reason, future monitoring efforts should include these species from this location.

"At the same time, more stringent policies are needed—especially in Asia—to reduce releases of mercury into the atmosphere, which eventually make their way into the oceans and into the fish we eat."

The researchers also looked at blue marlin in their latest study. But the data for that fish did not allow for a fair comparison among years.

The work involved reviewing previous studies that reported data for individual fish, including approximate location and year of capture, mass and total mercury concentration in white muscle, measured in parts per million in wet tissue. For yellowfin tuna, fish from 49 to 168 pounds were used. For bigeye tuna, fish from 35 to 168 pounds were used.

For both bigeye and yellowfin tuna, Drevnick and Brooks found that mercury concentrations in fish tissue rarely exceeded the U.S. Food and Drug Administration's "action level" of 1 part per million of methylmercury—the toxic organic form of the element—in an edible portion.

"The FDA action level is defined as 'a limit at or above which FDA will take legal actions to remove products from the market,' and according to the limit and the data here, no action should be taken," they wrote.

The U.S. Environmental Protection Agency has a "fish tissue residue criterion" for methylmercury that applies to freshwater and estuarine fish and shellfish—but not to marine fish such as tuna. Even so, the authors note that the average mercury concentrations for both yellowfin and bigeye now exceed the EPA criterion and that "consumers of yellowfin tuna and bigeye tuna caught in the North Pacific are not protected from adverse effects of mercury."

The latest study confirms and expands on work Drevnick and his colleagues reported in 2015 for Pacific yellowfin tuna. That paper, also published in Environmental Toxicology and Chemistry, reported that mercury concentrations in yellowfin tuna caught near Hawaii increased by at least 3.8 percent per year from 1998 to 2008.

Explore further: Mercury levels in Hawaiian yellowfin tuna increasing

Related Stories

Mercury levels in Hawaiian yellowfin tuna increasing

February 2, 2015

Mercury concentrations in Hawaiian yellowfin tuna are increasing at a rate of 3.8 percent or more per year, according to a new University of Michigan-led study that suggests rising atmospheric levels of the toxin are to blame.

Mirroring a drop in emissions, mercury in tuna also declines

November 10, 2016

For years, public health experts have warned against eating certain kinds of fish, including tuna, that tend to accumulate mercury. Still, tuna consumption provides more mercury to U.S. consumers than any other source. But ...

Overfishing threatens Pacific tuna

December 2, 2012

Asia-Pacific fishing experts on Sunday warned against depleting tuna stocks, saying the region needs to reduce its catch of the vulnerable bigeye species by 30 percent.

Recommended for you

Study: With Twitter, race of the messenger matters

February 23, 2019

When NFL player Colin Kaepernick took a knee during the national anthem to protest police brutality and racial injustice, the ensuing debate took traditional and social media by storm. University of Kansas researchers have ...

After a reset, Сuriosity is operating normally

February 23, 2019

NASA's Curiosity rover is busy making new discoveries on Mars. The rover has been climbing Mount Sharp since 2014 and recently reached a clay region that may offer new clues about the ancient Martian environment's potential ...

Researchers engineer a tougher fiber

February 22, 2019

North Carolina State University researchers have developed a fiber that combines the elasticity of rubber with the strength of a metal, resulting in a tougher material that could be incorporated into soft robotics, packaging ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.