Aquaculture works a lot better at sea than in coastal areas. It’s not particularly hard. Nets descending from anchored pontoons, with hatchery fish raised inside the nets, the water kept clean and aerated by the ocean current.
This avoids coastal pollution, and a lot of the parasite and disease problems.
Importantly, while enormous fish farms could provide huge amounts of food, the technique can also be used to restore populations depleted through overfishing. After they are a certain size, then nets are moved so that they will meet up with the natural fish of their species, then opened, hopefully to cause a “breeding frenzy”.
Is that being done?