Aus is pretty strict but how strict when it comes to the rising level of mercury makes it hard to meet the standards I don`t know.I think it was in Choice magazine I read way back in high school that the "safe" level was raised due to the decreasing number of the catch that met the standards.
At the end of the day we have to go for the best of the worst.No food these days is completely safe when it comes to hormones,steroids,pesticides,heavy metals etc. but by eating right you will cut down the risks.