RAPID CITY, S.D. (AP) — The list of South Dakota lakes with worrisome levels of mercury in fish grew again in 2012, but state environmental specialists say that doesn't mean people should stop eating fish.
Three lakes were added last year to the existing list of 12 where the state recommends limiting consumption of certain fish species, the Rapid City Journal reported (http://bit.ly/UTiDXo ). They are Elm Lake in Brown County, for walleyes 22 inches and longer; and lakes Minnewasta and Middle Lynn in Day County, for walleyes 18 inches and longer.
An existing mercury advisory for walleyes 18 inches and longer at Island Lake in Minnehaha and McCook counties also was extended to include smallmouth bass 18 inches and longer.
Mercury is a naturally occurring element that also finds its way into the environment through industrial activities, such as coal-fired power plants and improper disposal of products containing mercury. It passes up the aquatic food chain and ultimately to predators such as walleyes. The toxic metal can harm people's health.
"I think the big message is that fish is still an important source of protein with its omega 3 oil," said state Department of Environment and Natural Resources spokesman Patrick Snyder. "We're not recommending not eating fish but just limiting consumption of these fish that have advisories."
Mercury in South Dakota lakes likely is related more to nature than to pollution, John Lott, chief of aquatic resources with the state Department of Game, Fish and Parks, told The Associated Press. There is not a lot of heavy industry such as power plants in the state, he said, and numerous lakes have seen fluctuations in water levels that can lead to more mercury. Plants that grow during periods of low water decompose in high-water conditions, producing bacteria that changes mercury into a form absorbed by fish tissue, he said.
The mercury in at least one lake — Coal Springs Reservoir in Perkins County — is linked to a coal seam that was mined. But in general, "the ups and downs in water levels is the main thing we can put our finger on," Lott said.
The 15 lakes on South Dakota's list are out of a total of 160 bodies of water in the state that have been tested for 25 potential contaminants including mercury since 1994. The other 10 are Newell Lake in Butte County, Reid Lake in Clark County, Pudwell Dam in Corson County, Bitter Lake and Opitz Lake in Day County, Lake Isabel in Dewey County, the West Highway 81 ponds in the Twin Lakes complex in Kingsbury County, Twin Lakes in Minnehaha County, Lake Hurley in Potter County and Lake Roosevelt in Tripp County.
Details of the advisories for individual lakes can be found at http://www.doh.sd.gov/Fish/DeFault.aspx .
Information from: Rapid City Journal, http://www.rapidcityjournal.com