Steamboat Springs State officials are cautioning pregnant women and young children against eating bass caught in Elkhead Reservoir in Moffat County.
The Colorado Department of Public Health and Environment and the Colorado Division of Wildlife issued a joint news release Wednesday, alerting the public that tissue samples taken from fish in the reservoir revealed at least one largemouth bass and one smallmouth bass containing mercury levels of more than 0.5 parts per million.
"Eating fish that exceed this level may cause health problems, especially for the unborn fetus and small children," the agencies cautioned in a written release. The release explained mercury can harm developing nervous systems in fetuses and young children.
However, Randy Hampton, of the Colorado Division of Wildlife, said the fishing public does not need to be alarmed by the report.
"This is not an emergency," Hampton said. "It's not a ban. This is an advisory."
The Department of Health is advising pregnant women, nursing women and women who plan on being pregnant against eating any largemouth bass greater than 15 inches in length or smallmouth bass of any size. The advisory is extended to children 6 years or younger.
In addition, the general population is cautioned not to eat more than one meal of bass from Elkhead per month. A meal is considered 8 ounces of fish for an adult and 4 ounces for a child.
Less strict cautions also have been issued against northern pike and black crappie caught from Elkhead.
Steve Gunderson, director of the Division of Water Quality Control, said for the general population, moderation is the key when it comes to eating fish from a population known to have elevated levels of mercury.
"It's really a function of how much you eat," Gunderson said. "Fish is good for you to eat. Eating lots of fish with high levels of mercury is not good."
Previous tests on pike from three different stretches of the Yampa River did not turn up any fish exceeding the 0.5 parts per million threshold. Pike from Stagecoach Reservoir near Oak Creek were tested in 2008, but those fish did not show mercury concentrations that would call for an advisory, Gunderson said.
Airborne inorganic mercury can come from a variety of sources and typically finds its way into water bodies via precipitation. The Department of Health's Air Pollution Control Division is in the midst of a statewide effort to reduce mercury emissions from coal-fired power plants.
Gunderson said the presence of elevated levels of mercury in fish is not a sign that the water in the lake they swim in is unsafe for human consumption. He added that inorganic mercury in the water column does not accumulate in humans.