The reason I avoid farmed salmon; in Norwegian, science does not support this, but the pictures show the seabed close to the farms is actually a sewage. Not cleansed. http://www.youtube.com/watch?v=SeJSZEmwD80&sns=fb
So, what has this to do with my post; only that our government want to sell the salmon, and never show these films, pictures to any of their customers. The science done on this show of course no damage.. short term.
Experience show something else, that is when we send divers down to the seabed; which is of course not scientific.
Also experience / knowledge is when we eat the salmon, long term, several times a month as recommended over here.