Hi there and thank you for your question!
Most fish and shellfish contain a small amount of mercury, a toxic metal that can cause poisoning and serious health problems (1). Large fish that prey on small fish tend to have the highest levels of mercury, such as shark, swordfish, king mackerel or tilefish (1). The Food and Drug Administration recommends that adults can enjoy up to 12 ounces of a variety of cooked seafood per week as long as they avoid eating these large fish and follow the safety advice from local seafood advisories (1).
For women who are pregnant or breastfeeding and children 12 years old or younger:
Enjoy up to 12 ounces of fish and shellfish with low levels of mercury, such as shrimp, canned light tuna, salmon, pollock and catfish
Follow these same recommendations when feeding young children but serve smaller portions
Hope this helps!
Anna Ng, RD
1. "What to do about mercury in fish." Harvard Health Publishing. Updated July 2017. Accessed December 2020. https://www.health.harvard.edu/staying-healthy/what-to-do-about-mercury-in-fish