sadly, no.
if you have a pet fish on Animal Crossing, and you want a baby version of that fish, it isn't possible. you can get another kind of that fish, though, if you catch it with your fishing pole.
Chat with our AI personalities
Only Wendell, the wandering artist, and Chip, the Fishing Tourney judge, can eat fish. You can carry fish in your pockets, donate them to the museum, display them in your house, or release them into the wild. You aren't allowed to mail fish to other players, or drop them on the ground for other players to pick up.
No, you cannot breed animals on Animal Crossing.
Since animals are your neighbors with personalities just like humans, they choose what they want to do, and thus, no breeding. Plus, Animal Crossing is a children's game, rated E for everyone by ESRB, and wouldn't be that rating if you could breed.
OK, listen to me now... BIRD and FISH, its logically impossible that you can put a fish into a bird bath. think about it, your chances of you being able to pull of something like that, would be, I don't know...
ONE in about, a MILLION! think about it...