Mercury in Fish and Shellfish

Nearly all fish and shellfish contain mercury. Some fish and shellfish contain higher levels of mercury that may harm an unborn baby or a young child's developing nervous system. The risks from mercury depend on the amount of fish and shellfish eaten, and the levels of mercury in the fish and shellfish. Women who want to become pregnant, pregnant women, nursing mothers, and young children should avoid certain fish and eat fish and shellfish that are lower in mercury.



  • Shark.

  • Swordfish.

  • King mackerel.

  • Tilefish.

  • Marlin.

Eat no more than 6 ounces (one average meal) a week of:

  • Albocore (white) tuna per week.

Eat no more than 12 ounces a week of:

  • Shrimp.

  • Canned light tuna.

  • Salmon.

  • Pollock.

  • Catfish.

Check local advisories about the safety of fish in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters. Do not eat any other fish during that week.


What is mercury and methylmercury?

Mercury happens naturally in the environment and can also be released into the air through industrial pollution. Mercury falls from the air and can collect in streams and oceans and is turned into methylmercury in the water. It is this type of mercury that can be harmful to an unborn baby and a young child. Fish absorb the methylmercury as they feed in these waters and it builds up in them. It builds up more in some types of fish and shellfish than others, which is why the levels vary.

Why should I be concerned about methylmercury if I want to become pregnant someday?

If you regularly eat types of fish that are high in methylmercury, it can collect in your blood stream over time. Methylmercury is removed from the body naturally, but it may take over a year for the levels to drop a lot. Thus, it may be present in a woman even before she becomes pregnant. This is the reason why women who are trying to become pregnant should also avoid eating certain types of fish.

Is there methylmercury in all fish and shellfish?

Nearly all fish and shellfish contain traces of methylmercury. However, larger fish that live longer have the highest levels of methylmercury because they have had more time to collect it. Large fish pose the greatest risk.

What about fish sticks and fast food sandwiches?

Fish sticks and fastfood sandwiches are commonly made from fish that are low in mercury.

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.

Where do I get information about the safety of fish caught by family or friends?

Before you go fishing, check your fishing regulations booklet for information about recreationally caught fish. You can also contact your local health department for information about local advisories.