Many people have read the dire warnings about the health consequences of consuming fish and shellfish.  These admonishments usually center on mercury contamination—most of which is produced by coal-fired facilities, chlorine production, and mining—which is converted to an organic form of mercury (methylmercury) by the action of various aquatic micro-organisms.  This organic form of mercury comes to be located in marine animals and bioaccumulates as one ascends the trophic ladder as progressively larger animals consume smaller ones.  Mercury is a real threat because it is linked to cognitive impacts in children (e.g., loss of IQ points, problems with attention, decreased memory function) and various health effects in adults (e.g., cardiovascular disease, autoimmune disease).  People are frequently told (through various media) to limit fish consumption to prevent mercury poisoning.