Great lakes caught is okay, fairly low in mercury. So it depends on where you are/where fish came from.
^^ that says if it's minnesota caught and less than 20 inches you can eat it once per month. Longer than 20 inches and minnesota caught then no because minnesota lakes and rivers have high levels of mercury.
http://www.health.state.mn.us/divs/eh/fish/eating/safeeating.html