Here is an article (Sustainable Aquaculture: Net Profits) about a fish farm in Andalusia, Spain, which has a different angle than industrial intensive fish farms.
It refers to a number of arguments, such as feces contamination and lower densities, that I had mentioned in a previous article (The lessons of intensive animal husbandry to aquaculture). It also illustrates what I presented in Value chains are a great way to develop a niche, as they market their fish as the pata negra of sea bass at a premium price.
Of course, this farm is an example showing a very specific situation in a very specific environment, and providing seafood to the world population might require more intensive systems. Moreover, not everyone can afford to buy the pata negra category of food.