'Safe' Mercury Levels in Fish Based on 'Bad Data'br Commonwealth Club - The Commonwealth Club of Californiabr Jane Hightower will discuss the risk of consuming too much mercury when eating top predator ocean fish such as tuna, swordfish and sharks.She is a San Francisco doctor who discovered in 2000 that many of her patients had the classic symptoms of mercury poisoning, including nausea, trouble concentrating and tiredness, and she traced these symptoms to eating fish several times a week.