Study finds mercury in national park fish

Federal scientists have found high amounts of mercury in sport fish caught in remote areas of Western national parks, including Glacier National Park, according to a study released Thursday.

Researchers for the U.S. Geological Survey and National Park Service said that most fish they caught had acceptable levels of mercury, but 4 percent exceeded healthy levels.

Mercury occurs naturally, but scientists say its presence in national parks, which are supposed to leave wildlife unimpaired for future generations, was cause for concern.

Among the most widespread contaminants in the world, mercury can damage the brain, kidneys and a developing fetus. Fish and the birds and other animals that feed on them also are at risk, the report said.

Clint Muhlfeld, a Geological Survey fisheries biologist based at Glacier Park, said it has been previously documented that mercury exists in fish in the park, but levels vary from one lake to the next.

The most recent work in Glacier detected relatively high mercury levels in bull trout and lake whitefish in Lake McDonald. Testing conducted in 2008 found mercury in fish from two other Glacier Park lakes, but with lower mercury levels than were detected in the most recent study.

Muhlfeld finds those variations to be interesting.

“There’s been no comprehensive assessment of the park all at once to determine if mercury is an issue,” he said. “Because [the recent study] is isolated to one lake, it warrants more research for sure.”

The two agencies behind the study don’t regulate health guidelines, but the National Park Service said it is working with officials in the 10 states studied on possible fish consumption advisories.

“For us this is a wakeup call,” said Jeffrey Olson of the National Park Service. “We’re charged with keeping their habitat in good condition so generations to come visiting these parks can see what these landscapes look like.”

In the study, researchers caught 1,400 fish between 2008 and 2012 at 86 lakes and rivers in 21 parks including Glacier, Yellowstone, Mount Rainier National Park and Yosemite.

In two Alaskan parks, the average level of mercury in fish found bypassed the federal standard for human consumption.

The amounts of mercury also exceeded healthy levels at parks in California, Colorado, Washington and Wyoming, the study found.

Mercury occurs naturally from sources such as volcano eruptions, but pollution from burning fossil fuels is the leading contributor, the study said.

The results are not surprising because pollution in the atmosphere is a global problem, said Olson, adding that these findings call for a better understanding of how mercury is introduced into the remote corners of nature and the risks.

Mercury has been found in fish from other lakes in Northwest Montana, including Flathead Lake. State and tribal officials recently updated guidelines for consumption of lake trout from Flathead Lake.

The guidelines recommend that people avoid eating lake trout larger than 30 inches. Generally, the older and larger the fish, the more mercury they contain.

Online:

The report can be found at http://pubs.usgs.gov/of/2014/1051/pdf/ofr2014-1051.pdf