The problem with salmon is that farming, as it is now done, is impacting the wild populations which are already depressed in just about every river system.
Tuna do take a long time an a lot of energy to get big, but some fish higher in the trophic levels are extremely fast, like mahi-mahi.
Sustainably harvested shrimp, crab, lobster, sardines, anchovies, etc... would be more like eating chicken and pork. However, making our garden amendments from those fish clashes with any plan for global food security.
Von has it right - Jaykush's lead is the one to follow if you are putting stewardship first.
Since actions speak louder than words, I am only whispering virtue, and shouting irresponsibly.
As you know I live close to those 'farms'. It is not necessary as just the same quality can be attained growing them in freshwater tanks/ponds. Did you know we had the largest recorded sockeye run last fall? Put some in my freezer.