This is completely true, and also why it will never happen. While the evidence it not 100% certain (and rarely is anything in science)a all the pieces point to harmful effects of these operations on wild salmon, even if only one of multiple possible vectors for their deleterious influence is true. They are not the only issue facing wild salmon to be sure, but I personally believe they should be eliminated. However, the reality is it has become established as a significant industry, employing a significant number of people and the industry lobbyists are quite powerful. Even if a smoking gun comes out on effects, the governments (Provincial and Federal) do not have the courage to take action and responsibility for the economic consequences of doing so.
The hope is land based operations. They very likely will become viable (and already are) , and eventually will probably replace these net operations, but its also a reality BC may not be part of that revolution. Cheap land and close access to markets will determine where those operations are based, and unfortunately it likely wont be in BC with high land prices and remote locations. The worlds largest land based operation was just announced in Maine. Cheap land, close to Boston, NY and other major US markets.
https://www.seafoodsource.com/news/...-land-based-salmon-farms-to-be-built-in-maine . This operation will eventually produce 33,000 tons annually. According to the BC Salmon farmers association website the entire industry in BC produces 75,000 Tons. So the hope to eliminate these farms lies not in government as they are unlikely to act, but technological change coupled with continued exposure of the practices of net pen farming so that consumers, once they have a choice of buying from operations like the Maine one, can choose the more environmentally friendly land based product at a similar cost. I am optimistic market forces and continued painting of net pen farms as environmental pariahs will eventually win the day.