Norway has grown so fed up with the environmental damage of in-ocean fish farms that it stopped auctioning them off in 2014. It has been giving out licences for free to set up on land. That represents a subsidy of $9- to $12-million dollars based on the auction price.
Note that Norway has long had a speculative market in the licences themselves with purchasers turning around and selling them for millions in profits. Kjersti Sandvik's book, Under the Surface, from Gyldendal, details this period. The price of licences reflects that fish farms are a licence to print money, averaging 23- to 25-% profit. At the same time, fish farms are susceptible to many calamities that wipe them out. That is why the industry is a boom/bust one, with the accumulation of the biggest lasting as a cartel, the smallest who can't weather storms, collapsing.
Only new ideas that separate farmed fish from the the ocean are being considered. Here is a good review article: http://salmonbusiness.com/deadline-day-for-bold-marine-concepts/. The deadline day was Nov 17, 2017.
You will note, however, that while proponents talk about sequestering fish from the environment, it is more about making more money, than downstream damage, like sewage, that fish farms don't pay for. Marine Harvest says its egg prevents lice and escapes, it only started 'suggesting' it might do something about sewage, in the above post, three years after Norway stopped auctioning in-ocean licences. Hmm.
Note in the diagrams of the five in this article that you are looking right through some, as in sewage/disease/feed direct to the environment.
And these include the Havfarm concept which is about massive increases in stock in flow through containers, that are mega-farms offshore where they can release there sewage, etc. in a place where the public won't complain. Sorry, it's straight forward to be cynical when the text for these things are long on how big they are and the money to be made, but short on everything else.