You can pretty much guess what bait to use since it goes from lowest level fish to highest level fish. Once you know that a certain fish, like Fullmoon sardines for example are level 30-ish, and you see it in your log, you can judge accordingly on what level bait you're using for higher or lower level fish. That's how you make some money - try to zero in on the fish you want and adjust bait accordingly to only catch that.