Interestingly, Washington State (US) banned this back in 2017. I remember when I was younger actually getting these kinds of farms pointed out on a boat trip. The boat captain mocked them because they still legally called themselves "wild caught", since they existed in open water instead of farms.
I assume they ban the use of open net and not something like this which reduces the harms of the open net style. concentrating the excrement on the bottom of the floor being a big one and polluting the sea with lice treatments being another one.
https://www.dnr.wa.gov/news/board-natural-resources-ends-ope...