The Oklahoma Department of Environmental Quality monitors mercury levels in many species in lakes across the state and releases annual updates about how often people can safely eat those fish. The most recent update came last week.

“We certainly encourage Oklahomans to go fish, to eat, the fish they catch, but to be mindful of their choices,” said Erin Hatfield, the DEQ’s Communications Director. “We want people to have all the information they can to make good, healthy decisions for themselves and their families.”

Mercury is a metal that gets into the atmosphere from mining, manufacturing, coal-fired utilities and sometimes volcanoes. Then it dissolves into water, where fish absorb more and more over their lifetimes.

“The bigger the fish, the older they are, so they’ve had more time for that mercury to accumulate,” Hatfield said.

Predatory fish also tend to have higher mercury content, because they eat other fish and absorb their mercury. So most of the advisories aim to limit how often people eat large, predatory species like many bass and catfish.

“It's really important that people look at the advisory for the lake where they intend to go fishing, because you can't look at Atoka and think that it will be the same advisory for Broken Bow,” Hatfield said. “They’re all very different.”

The guidelines are also different for children under 15 and people who are nursing, pregnant or able to become pregnant. Those populations are more sensitive to mercury.

To learn about the specific guidelines for your favorite Oklahoma fishing spot, you can read the most recent Mercury in Fish Guide. It also lists lakes and species that were tested and found to contain safe levels of mercury — those species in those lakes can be consumed as often as they’re caught.