I actually had an idea concerning this. You know how there was a HUMONGOUS unfish-able shadow in the GCN version on the way to the island? Well they should have that in a new game, have it fish-able, and make it a special visitor character who is a whale!
We have frogs and octopi as villagers
And both those species can be caught and donated. :U
So yeah with that I don't find villager species being based on things that can be caught really all the strange since like stated above we already have two.