Mercury rising

Anglers who prefer to catch and eat their fish—rather than catch and release—have updated guidelines from the Wyoming Game and Fish Department (WGFD) and the Wyoming Department of Health in regards to fish consumption.

The new consumption guidelines, announced in a July 11 press release from the WGFD, provide recommendations on healthy servings of fish while limited mercury consumption to safe levels. According to the press release, the 2022 consumption guidelines are “simplified and consistent with guidance from the Environmental Protection Agency and the Food and Drug Administration on threshold for mercury.”

These new advisories are limited to information specific to sensitive individuals, including those who might become or are pregnant or breastfeeding and children under 12 years of age. There are no restrictions on consumption for men over 12.

These simplified guidelines place recommendations by species of fish into “best,” “good” and “choices to avoid” categories. Under the recommendations, people can eat two to three servings of fish a week from the “best choices” list or one serving a week from the “good choices” list.

For adults, one service is four ounces. For children, one serving varies on age with one serving being one ounce for ages 1-3, two ounces for ages 4-7, three ounces for ages 8-10 and four ounces for ages 11 and above.

Included in the ‘best choices” category are trout under 10 inches, freshwater drum and kokanee salmon. The “good choices” category includes trout 10 to 15 inches in size, bass less than 12 inches, black crappie less than 10 inches, burbot less than 20 inches, channel catfish less than 20 inches, sauger and walleye less than 12 inches and yellow perch of any size.

The “choices to avoid”, which have the highest mercury levels, include trout greater than 15 inches, bass greater than 12 inches, black crappie greater than 10 inches, burbot greater than 20 inches, channel catfish greater than 20 inches, sauger and walleye greater than 12 inches and any size of northern pie and tiger muskie.

According to the WGFD, mercury is “a widespread and naturally occurring element and some soil and geologic formations naturally have higher levels of mercury. Most mercury pollution occurs as atmospheric deposition related to energy consumption and production, and industrial processes. Mercury may also enter Wyoming waters via household refuse, batteries, mining, and industrial wastes.”

Once in a body of water, such as a lake, mercury is converted to methylmercury by bacteria and other processes. This is then absorbed fish through their food and from water. As fish get larger and older, the mercury levels increase. This means that smaller Wyoming-caught fish are a better option to be saved fro eating.

Predatory fish, such as walleye, burbot and large trout often accumulate more mercury because they eat other fish. There is no method of cooking or cleaning fish which will reduce the amount of mercury in a fish.