I'm no expert but that seems like it could be very energy intensive. All the systems to maintain water quality, temperature. Not to mention the problems that arise having fish in such high density.

There are other places in the world that farm salmon at a much lower density which helps in terms of disease and bioload on the environment. There's a company in New Zealand attempting to build open ocean fish pens, they might already have a prototype out already can't remember. Different species of salmon though.