Freshwater fish low in mercury include: Wyoming-caught trout and farm-raised tilapia and catfish.

Freshwater fish high in mercury include: channel catfish, sauger, and walleye from Big Horn, Seminoe and Pathfinder reservoirs.

Mike Stone, fisheries chief with the Wyoming Game and Fish Department, explained that fish size is a factor affecting mercury levels.

"The longer a fish lives the greater its chances of accumulating mercury in its tissues," Mr Stone said.

"In general, fish that feed on other fish or bottom-feeders are also more likely to accumulate mercury."

Game and Fish has conducted baseline surveys on major reservoirs around the state for several years. Fish from the majority of waters exhibited low levels of mercury. A few waters warranted additional testing, which led to the fish consumption advisory. Mercury is a naturally occurring element that is distributed throughout the environment by both natural processes and human activities.

Specific recommendations are available on the Department of Health’s website and are included in the 2008-09 Wyoming Fishing Regulations, which will be available at Game and Fish offices and license selling agents on 1 January 2008. The recommendations include information about various fish types and bodies of water in the state, and are based on current information from the Wyoming Game and Fish Department. Future guidelines may change as further testing results become available.

Ryan emphasized that finding mercury in fish is not unique to Wyoming.

"In fact, all other states except Alaska have previously issued similar fish consumption advisories for their citizens."