I don't think the government would have anything to gain by commiting false tests to stop you from eating Fish/Seafood.
The top link shows mercury contents of tested fish. They recommend you limit fish/seafood intake but if you're eating low risk seafood or you're in a general area that has lower contamination risk- I wouldn't worry about it.
As LeiYunFat said, lmit intake of large fish and predatory fish as they always have larger concentrations due to the fact that they live longer and consume other fish (with mercury content).
One important observation: Chunk light is lower in mercury than albicore. Its cheaper, and I don't think it tastes "better" anyway. Remeber- water, not oil.