Fish consumption frequently requested information

Fish consumption flyer

Pregnant or young child DO NOT EAT:

  • Shark.
  • Swordfish.
  • Tilefish.
  • King mackerel.
Learn more

Sources of mercury

In Colorado, mercury is the most prevalent contaminant in fish. Mercury is a naturally occurring element in the environment. Certain natural events, such as forest fires and volcanic eruptions, contribute mercury to the atmosphere. Precipitation brings this contaminant down into water bodies. Human activities such as gold mining, chemical manufacturing, power generation, and incineration also increase the amount of mercury in the environment.
Health risks of mercury-contaminated fish
Mercury can accumulate in your bloodstream and may harm your nervous system. Young children, developing fetuses and breast-fed babies are at the greatest risk because their nervous systems are still developing. By following the statewide fish consumption guidelines and site-specific guidelines, the nutritional benefits gained from eating fish should outweigh the potential exposure to the harmful effects of mercury.

Small fish, big fish

  • The amount of mercury in fish depends on the diet of the fish, the age of the fish and its location in the food chain. Mercury reaches higher concentrations in long-lived species and species of fish that eat other fish. Fish and shellfish are the main sources of mercury exposure to humans.
  • Smaller fish generally contain less mercury than older and larger fish. Rainbow trout, crappies, and yellow perch usually have lower levels of mercury because they tend to feed on plants or smaller aquatic organisms.
  • Predatory fish, such as walleye and lake trout, can accumulate more mercury because they eat other fish.


  • Mercury is bonded to the proteins in the fish muscle. Therefore, there's no cleaning or cooking method that will reduce the amount of mercury in a fish.
  • Some kinds of cooking can affect contaminants other than mercury. Some contaminants are stored in fish fat, and frying tends to seal these pollutants in. However, the EPA says if the fish is cooked in such a way that the fat is drained away, some of the pollutants can be removed.

Commercially available fish

Most ocean or farm-raised fish you find at the store or restaurant, such as salmon, tilapia, catfish, cod, shrimp or crab, contain low levels of mercury. The Food and Drug Administration recommends eating two meals per week of the low-level species. Some ocean fish contain high levels of mercury, and the FDA recommends children, pregnant women and women planning on becoming pregnant should abide by strict guidelines including not eating from the list below.

All states have advisories

All 50 states have some form of advisory for elevated contaminant levels in locally caught fish. There are currently over 3,700 fish consumption advisories for mercury on lakes or streams in the United States. Many states have also issued site-specific guidelines, similar to Colorado’s, to better inform and protect the people of their state.