All I need is a price check on raw and cooked fish in single, SC, and DC prices, the derp pig is to just bring people to this thread "He walking on water papa"
I would suggest not even looking into fish yet, as when 1.7 comes, the fish market will become much, much more profitable.
All the new fish types, and uses for the new fish. Currently all fish is good for is cats, and stocking malls so that others can get cats. Since likely only malls will buy fish in large quantities like you want to sell, they are probably looking ahead at the update, determining what will be in demand in the future. I suspect that normal fish will drop of greatly (because of fishing becoming easier), and the other fish will be hot items.