Frequently Asked Questions

Q. What is mercury and methylmercury?

Mercury occurs naturally in the environment and can also be released into the air through industrial pollution. Mercury falls from the air and can accumulate in streams and oceans and lakes. In or near sediments, bacteria change some of the inorganic mercury into the organic, more toxic methylmercury. It is this type of mercury that can be harmful to your unborn baby and young child. Fish absorb the methylmercury as they feed in these waters and so it builds up in them.

Q. Why are mercury levels higher in some fish species than in others?

Methylmercury is accumulated all along the food chain from tiny algae and invertebrates, to smaller fish to larger fish that eat the other fish, and to fish-eating birds and mammals, including humans. It gradually accumulates in the fish tissue over time, and the largest, long-lived that have been in the water the longest accumulate the higher levels of methylmercury.

Q. Is there methylmercury in all fish and shellfish?

Nearly all fish and shellfish contain traces of methylmercury. However, larger fish that have lived longer have the highest levels of methylmercury because they've had more time to accumulate it. In Northern Nevada waters, walleye, bass, wipers, and northern pike appear to accumulate the highest levels of methylmercury.

Q. I don't see the fish I eat in the advisory. What should I do?

Initial information about mercury levels in Nevada’s recreational waters is shown on the Nevada Department of Wildlife website at If you want more information about other fish that you eat, see the FDA food safety website or the EPA website.

Q. What if I eat more than the recommended amount of fish and shellfish in a week?

One week's consumption of fish does not change the level of methylmercury in the body much at all. If you eat a lot of fish one week, you can cut back for the next week or two. Just make sure you average the recommended levels.

Q. How do I decide whether fish consumption is appropriate for me or not?

Only you can decide whether consuming fish is right for you. Our goal is to provide you enough information to make your own informed decision about the net health benefit of eating fish.

Q. I live near a water with a health advisory for fish; does that mean I cannot eat the fish that I catch?

No it does not. First, check whether the fish that you catch is included in the health advisory. If it is not included, you can also check the specific fish species data for the fish that you catch and evaluate for yourself whether you want to consume that fish. To help protect human health, the Nevada Division of Health has issued species specific health advisories for waters where a fish species has an average methylmercury level above 1.0 ppm. Fish consumption advisories don’t mean you should stop eating all fish from affected water waters; fish is low-fat source of protein, and is a good source of omega 3 fatty acids. Simply limit consumption of the specific fish species to amounts specified in the advisory.