I'm not going to run down the whole list, but some of the worst from a mercury perspective -- shark, swordfish, and most types of tuna are listed here as "not okay to eat." May be there is a correlation between larger fish with the most mercury and fish that are more endangered.
The fish in my diet consists almost entirely of salmon and trout, and occasionally a tuna tartare (I would have a real hard time giving that one up.) I avoid farmed stuff.
There is actually a correlation: large, predatory fish accumulate the most mercury because they're highest on the food chain, and they also tend to be rare and slow to breed, and hence more endangered.
With farmed fish it basically depends on where it's farmed. It can be very healthy and sustainable, or quite terrible.
The fish in my diet consists almost entirely of salmon and trout, and occasionally a tuna tartare (I would have a real hard time giving that one up.) I avoid farmed stuff.