I get a lot of requests for information on the fish that have been found to have the lowest mercury contents and the following list comes from the compnay Nordic Naturals:

I will skip on the ones that are highest or medium, presuming that one would not want to eat those!

Anchovies, Calamari, Catfish, Clam, Cod, Crawfish, Flounder*, Haddock, (atlantic*), Hake, Herring, Mackarel, Mullet, Oyster, Perch (ocean), Plaice/Pollack, Salmon**, Sardine

Scallop*, Sole (pacific), Tilapia (Matia does not recommend this for those with IC), Trout (fresh water), Whitefish, Whiting.

*overfished, ** May contain PPCBs