I had an environmental ethics professor in college. Her pet cause was the plight of the atlantic bluefin tuna. She frequently lamented that only the cute animals get any real support.
If you're going to eat salmon anyway (and lots of people do), it's much less destructive to eat it factory farmed. This actually goes for every single fish.
There's a kind of a compromise going on here. Wild Salmon stocks are limited and were it not for farming demand would outstrip what's available. Apparently the tradeoff here is "dead zones" in the ocean unfortunately.
Of course, as I say, the farmed salmon is not the same fish as the wild one. The flesh is dyed pink. The flavour doesn't benefit from the wild salmon's varied diet, and the texture isn't developed by all that swimming upstream.
There is a very wide variance in the quality of farmed salmon too, to the point where you really can't be sure what you're eating unless you actually know the farm it's coming from.
I've heard it said that farmed salmon carries little of the health benefits of wild salmon. Personally I'd prefer to just pay a lot to eat salmon very rarely than to eat farmed salmon frequently. But everywhere you go there is otherwise indiscriminate demand.
Fish, though, yeah, they're not getting any cuteness bonus. Not much outcry about "factory farming" in aquaculture.
I have recently, and irrationally, stopped eating octopus because they're so smart. Maybe some viral videos of tuna doing amazing things would help...