SIOUX FALLS, S.D. (KELO) — In general, it’s safe to eat the fish caught in lakes and rivers in South Dakota, but there is a list of waters for which limited fish consumption is recommended.

The South Dakota Department of Health (DOH) lists 28 bodies of water in 20 counties with mercury fish consumption advisories. The waters are tested for mercury, pesticides and 23 other contaminants but it’s mercury levels that are the focus of consumption advisories.

The list is also found on the Department of Agriculture and Natural Resources (DANR) website and the state’s Game Fish and Parks fishing handbook. The list is for fish with levels of mercury. Mercury is an element that is found in the natural environment and is also used in industry. Fish take in mercury as they feed. Consuming too much fish that have mercury could cause health issues.

The Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) advise that healthy adults eat no more than seven ounces of fish per week with mercury levels close to or slightly above 1ppm.

The state’s testing system is a collaboration of the DOH, DANR and GFP.

“It’s three departments that work together, it’s a cooperative effort,” DANR environmental scientist Aaron Leingang said of the fish testing system in the state.

The three agencies determine which waters to test, Leingang said.

Fish testing is done on an annual basis that coincides mostly with population surveys that GFP does, Leingang said.

The state samples at least 10 lakes each year for a panel of 25 contaminants, according to the DOH.

“We don’t have the ability to test all the lakes all the time,” Leingang said. “Mercury levels have a tendency to not be very erratic it takes some for things to change. We can be up to maybe 10 years on a revisit.”

The DANR has an extensive listing of fish testing results on its website. Fish in the Angostura Reservoir were tested in 2014 and determined to be safe. More recently, fish in Kiesz Lake in McPherson County were tested in 2021. The public is advised to limit consumption of walleye that are 16 inches and larger.

“GFP does the bulk of the fish collection and they send those samples to DOH for analysis,” Leingang said.

“If we see water that maybe had some little bit higher numbers, we can go back and revisit that on a quicker basis,” Leingang said. That decision would be made by all three agencies, he said.

Travis Entenman of the Friends of the Big Sioux River, a non-profit that focuses on the quality and use of the Big Sioux River, said the source of mercury in the state’s lakes has not been determined.

“It could be coming in from other states,” Entenman said.

Walleye are the fish most negatively impacted by high mercury levels, according to the state’s list. Walleye were listed as limited consumption from at least 20 lakes. The size of the walleye in the advisory varied by lake but often, it was 18 inches or larger. Northern Pike were cited in at least eight lakes.