Glad to see you have an open mind Ian. What damage have you seen done to sensitive areas that is directly related to salmon farms?
Near a fish farm outside the mouth of the Mahatta River, a well known summer steelhead river, it is now a dead zone when previously it was teaming with life. And, after fishing the river several times I did not see anywhere close to the numbers of steelhead I have seen in the past.
Talking with a fisheries officer who did studies before and after a fish farm went into operation near Nootka Island, he told me there were drastic changes. Before the fish farm, a simple beach seine would show all 6 species of salmonids, as well as bottom fish of many species. There were even little seahorses and countless sea perch and sculpins. The area was very rich in sea life of all sorts. A year after the fish farm went into operation the area was almost a complete dead zone and only a few fish species were captured in several beach seines in the exact same location.
My only conclusion, from a layman's long term study, is if it walks like a duck, quacks like a duck and looks like a duck, then chances are that it is a duck.