That's a distal problem, an end result. The root problem is overcrowding. Anyone who's ever kept fish knows two things: how tempting it is to overcrowd your tank, and what a disaster it is when you do. The obvious problems that stem from overcrowding are difficulties keeping the tank clean, and outbreaks of parasites or disease. In between those is the plain fact that overcrowding stresses fish. You can pump, filter, medicate, do all kinds of things -- but you can't make that stress go away without reducing the population. Crowded fish are stressed fish, and stressed fish are unhealthy fish, and something is going to go wrong sooner or later.
Fish farming seems like such a great idea. But it's vastly inferior to the sustainable harvest of wild fisheries. Overfishing has led to people doing things that are troublesome in other ways, like aquaculture. The fish aren't just crowded, they're often drugged and fed such a bad diet that they don't develop properly. Farmed salmon isn't pink because the fish don't eat the right foods, so the farmers dye it to make it look like healthy salmon. Not really something I want to eat.
So, let Neptune teach the fish farmers a lesson that most people learn with guppies. Meanwhile, focus on efforts to rebuild natural habitat. You want to eat salmon? Any tribe that does can tell you those fish don't give it out for free. You have to honor them by protecting the rivers and streams where they breed, and not take too many, or they will leave you to starve. Better habitat upstream equals more fish to eat.
Here are some practical ways to support wild salmon:
And after you've done that, pray. These fish will communicate back and forth with two-legs, which is rare. Use it. Back the tribal peoples who are working to support the salmon; they know what they're doing.