I used other fish I had caught, but you can also use flowers and fruit that you have harvested/caught. I fished out numerous pomegranates from that pond, and they were a bait option (though I didn't use them because I wanted to plant them). I'm still pretty new to fishing as well! You receive a notification if you catch a bait specific fish. Ex: You caught a Piranha! Then beneath that it will say Bait: Bass. That's the only one I remember unfortunately, as I just started fishing last night. I don't see a fishing bait guide up just yet either. Sorry I couldn't be of more help! Fishing is not something I normally paid much attention to in my sim games, but it has been very useful in TS4 so far, so I will definitely be checking out the finer details more today.
