My doctor told me that I could eat tuna occasionally while pregnant and according to this website, it's higher in mercury than sea bass.
http://www.*****************.org/pregnancyhealth/fishmercury.htm
A little bit won't hurt. I ate shrimp once a month while pregnant and it's on the "no no list" and both of my boys are fine. If you eat excessive amounts that's when it gets dangerous. My ob said 3 oz / week of the "bad" seafood wouldn't affect the pregnancy.