We are told that fish are good for us... but studies have found that not all fish are healthy. High amounts of mercury in fish are causing concern for children and families. Mercury contaminates water systems and soil when it rains. As fish feed on one another, the mercury stores up in their bodies. The toxic metal affects the nervous system. And although studies have shown large amounts of mercury can also affect fertility and blood pressure, and memory loss in adults, it's particularly dangerous to young children. Prenatal and infant mercury exposure can cause poor mental development, deafness and blindness. Even in low doses, mercury may affect a child's development, delaying walking and talking, shortening attention span and causing learning disabilities. So what fish should you stay away from or limit your amount? Some say shark, swordfish and fresh tuna are all candidates of unsafe fish. Good fish on the other hand to eat would be salmon, cod, tilapia and haddock.