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The Nevada State Health Division has issued health advisories that recommend limiting consumption of fish species from six Northern Nevada waters, due to elevated methylmercury levels.
The Nevada Department of Wildlife, the Nevada State Health Division and the Nevada Division of Environmental Protection are working together to identify and monitor potential mercury risks to the public.
The health advisories recommend no consumption of fish from Lahontan Reservoir and the Carson River from Dayton downstream to the reservoir; no consumption of white bass from Little and Big Washoe Lake; no consumption of wipers and walleye and no more than one eight-ounce meal per week of any other fish from Rye Patch Reservoir; no consumption of walleye from Chimney Dam Reservoir; and no consumption of large mouth bass or northern pike from Comins Lake.
Mercury in lakes and rivers is converted into methyl mercury by certain bacteria. Fish ingest methyl  mercury by feeding in affected water. Larger predator fish eat smaller fish, thereby accumulating their mercury as well. The fish kidneys do not expel mercury, and it gradually bio-accumulates. Over time, methylmercury is carried up the food chain, and its concentration increases in the larger predator fish.
The Nevada Department of Wildlife collected edible fish tissue samples from 39 recreational waters over the past 18 months. Initial results on 25 waters, with 351 individual fish sampled has shown that Comins Lake, Chimney Dam Reservoir, Lahontan Reservoir, Rye Patch Reservoir and Little Washoe Lake, each had multiple fish species with average wet weight methylmercury levels of 1.0 parts per million or more.
The samples were analyzed by the Environmental Protection Agency in Richmond California. The fish with the highest mercury levels were older, larger predator fish, such as wipers, bass, and northern pike.
The bottom line is: Nevadans should feel free to enjoy fishing in the state’s waters and to enjoy fish they catch as an important and healthy part of their diet. Pregnant women, nursing mothers, and small children should limit their consumption of fish; choose smaller fish rather than larger older class fish for consumption, or practice catch and release when fishing on the waters where health advisories are in effect.
The following are Health Advisory sheets for the affected waters. These sheets include tables that break down mercury levels and recommended meals per month by water and species.
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There is no health advisory for Wildhorse Reservoir. The Nevada Department of Wildlife is providing this data
to the angler community for informational purposes only.
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Frequently Asked Questions
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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.
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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.
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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. |
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 www.ndow.org If you want more information about other fish that you eat, see the FDA food safety website or the EPA website. |
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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. |
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. |
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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.
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