Fish contaminated by high mercury levels

Popular fishing destinations Rifle Gap and Juniata reservoirs are among a handful of western Colorado lakes added last week to the growing list of waters with fish contaminated by unsafe levels of mercury.

According to the Colorado Department of Public Health and Environment, anglers should strictly limit their eating of certain fish from Rifle Gap and Juniata reservoirs as well as Elkhead Reservoir near Craig, Catamount Lake near Steamboat Springs and Lake Granby.

The warnings will include signs posted at each place.

Although mercury poisoning can affect humans of all ages, pregnant women and children under age 6 are especially susceptible, said Steve Gunderson, director of the Water Quality Control Division of the Department of Health.

“Mercury can do immense harm to developing nervous systems in fetuses and young children,” Gunderson.

“Adults, too, are susceptible to problems with their central nervous and cardiovascular systems.”

Such consumption advisories aren’t new to western Colorado. Some reservoirs, such as Narraguinnep near Durango, have carried a similar warning for years.

Researchers are in the midst of a five-year study, looking for contaminated water around the state, Gunderson said.

Of the 112 tested, 23 (about one in five) had high-enough mercury levels to spark the fish-consumption advisory

Juniata, on the south side of Grand Mesa, is a water source for the city of Grand Junction.

Gunderson said drinking water containing small amounts of inorganic mercury poses no health concerns.

Kristin Winn, spokeswoman for the Grand Junction Department of Public Works, said mercury levels in Juniata are “undetectable.”

“We perform 20,000 tests each year to assure our customers have safe drinking water,” she said.

“We test for mercury down to .0002 milligrams per liter, and we can’t pick it up. At that level it’s considered undetectable.”

Problems come not from the minute amounts of dissolved mercury but how that inorganic mercury passes through the food chain.

Gunderson said at least one fish from each reservoir tested positive for excessive levels of mercury.

Division of Wildlife spokesman Randy Hampton emphasized the warnings are just that, not complete bans.

“This is an advisory, not a ban,” Hampton said.

“It’s not a health emergency, and people should not stop eating fish. However, they are advised to limit their consumption of some fish, but it doesn’t mean you have to stop fishing.”

Not all fish are susceptible to mercury contamination. Trout rarely are because their diet consists mostly of insects.

A compete list of waters and details of the advisories can be found at


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