As a group, fish are excellent sources of proteins, vitamins, and minerals. The troubling health dilemma is balancing the health benefits of fish against the harm that might be caused by its content of toxic chemicals – most of all, methylmercury. ~ American molecular biologist and nutritionist Marion Nestle
Methylmercury found its way into waterways and the oceans from its use in numerous industrial processes, including gold mining, where mercury is used for extraction. Coal-burning power plants emit mercury.
Once in the atmosphere, mercury is widely disseminated and can circulate for years, accounting for its widespread distribution. ~ US Geological Survey
Aquatically, methylmercury is the DDT of the seas. Methylmercury accumulates in animals up the food chain. Top predators may acquire concentrations in their tissues that are a million times higher than found in the water. These meaty fish are those favored for human consumption, including tuna, swordfish, bass, and herring, among many others.
Eating contaminated fish and wildlife exposes people and fish-eating wildlife to the most toxic form of mercury, methylmercury. ~ US Geological Survey
Mercury poisoning destroys the body: causing itching, peeling skin, loss of hair, teeth, nails, and bodily coordination, kidney and immune system dysfunction, and destruction of every aspect of the intelligence system, from sensory perception to cognition.