This is not true, and your figures make no sense.
Fish concentrate mercury by being high up in the predator chain, for example sharks (0.988 parts per million), swordfish (0.976 ppm), King Mackerel (0.730 ppm). Sardines are extremely low in the pecking order, and have typical mercury concentrations of 0.016ppm, certainly amongst the lowest levels for all sea fish.
Here is a mercury calculator:
http://www.gotmercury.org/Roony, I don't like to pick on someone, but you seem to just make things up. It isn't helpful when some people are coming here with real health issues, seeking true information. Perhaps if you want to make something up, just preface it with "I think" instead of stating it as a known fact.