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New Wyoming consumption guidelines caution bigger, older fish have higher mercury levels

Burbot, a nonnative fish species. (Lucy Wold, Wyoming Game and Fish Department)

CASPER, Wyo. — New fish consumption guidelines issued by the Wyoming Game and Fish Department and the Wyoming Department of Health caution people that bigger, older fish tend to have higher mercury levels than other fish.

Predatory fish like walleye, burbot and large trout also tend to have higher mercury levels because they eat other fish, Game and Fish said in a press release announcing the new fish consumption guidelines on Monday. There isn’t any way to cook or clean fish to reduce the amount of mercury, the department added.

The new fish consumption guidelines are specifically for sensitive individuals, including people who may become or are pregnant or breastfeeding and children under 12 years old.

The new consumption guidelines include recommendations specific to fish species and size, categorizing those into “best choices,” “good choices” and “choices to avoid” categories. The recommendations encourage sensitive adult individuals to limit fish consumption to 2-3 servings per week out of the “best choices” category or to one serving from the “good choices” category.


The recommendations for children suggest fish consumption should be limited to two servings of fish from the “best choices” list per week.

An adult serving of fish is four ounces, according to Game and Fish. Servings for children vary by age:

  • 1 ounce at ages 1–3
  • 2 ounces at ages 4–7
  • 3 ounces at ages 8–10
  • 4 ounces at age 11+
(Wyoming Game and Fish)

The Wyoming Game and Fish Department collected tissue samples from each species of fish included in the recommendations for mercury testing at an Enivronmental Protection Agency laboratory in Colorado.

“Game and Fish focused sampling on priority waters where lots of people keep and eat their catch and on species that people eat frequently like trout, walleye, sauger, yellow perch and crappie,” Travis Neebling, Aquatic Assessment Crew fisheries biologist who led the sample collection, said in the news release. “Those fish mostly come from lakes and reservoirs.” 


Wyoming’s new consumption guidelines are consistent with guidance from the EPA and the Food and Drug Administration in regard to mercury thresholds, Game and Fish noted.

“Mercury is a widespread and naturally occurring element, and some soil and geologic formations naturally have higher levels of mercury,” the release said. “Most mercury pollution occurs as atmospheric deposition related to energy consumption and production and industrial processes. Mercury may also enter Wyoming waters through household refuse, batteries, mining and industrial wastes. Once in a lake, mercury is converted to methylmercury by bacteria and other processes. Fish absorb methylmercury into their tissues from their food and from water.”

The full fish consumption recommendations are available on the Game and Fish website.