You are right! Fish and shellfish are good sources of high quality protein and other essential nutrients like omega-3 fatty acids. But, some types of fish do contain more mercury than others — eat these in limited amounts, or avoid them entirely. Keep in mind the following basic rules, and check out the FDA or EPA for more extensive info.
[ ] Never eat shark, swordfish, king mackerel, or tilefish.
[ ] Limit lower mercury fish such as canned light tuna, shrimp,salmon, catfish, and tilapia to 12 ounces (two average meals) a week.
[ ] Albacore “white” tuna has more mercury than canned light tuna, so limit your intake to one serving (six ounces) per week.
[ ] Fish sticks and fast-food sandwiches are usually made from low mercury fish. (And that's the only time we'll recommend the drive through!)