*Baits - each fish has a favorite bait, some baits it likes, others it is less likely to eat, and some it will never touch.
*Outside or in caves - some fish are only found underground. Rare fish can only be caught on special tiles (which are out at sea).
*Feeding Fishing height: How deep the fish swim
Water has several depths, allowing for fish to prefer a particular level:
*Top - near the surface of the water