Fish NPC prices.

[Alistaire]

Heck - they can even introduce the fish "Lottery" (similar to the new materia transmutation system) where you can turn a bunch of useless fish to get another smaller (most likely again useless) bunch of fish Make a few turns and you'll end up with one useless fish in the end

They've already said there'll be unique items from gutting fish. So I'm imagining something like what ffxi had mixed with 14's crafting system.