Let me be more clear, while fishing, there are things you can catch besides fish. One of these include bait for other fishing holes with different types or water. Example: you can catch a chub in a foul fishing hole, and use that chub in saltwater, or catch a shad in rivers and use the shad in the lakes.
I believe that the bait you revive when you catch - chub, shad, fish roe, and minnows should - have an increased drop rate to receive the rare fish, otherwise what's the point in using them? It's way easier to farm for worms, insect parts, guys, and crawlers than it is to fish and farm for chub, minnows, shad, and fish roe, so there should really be some type of benefit or added bonus while using them.
What do you guys think? Do you fish with your shad over your guts? Or choose your minnows over insect parts? I think it would be cool to have a bait that increases the rare fish catch, like the pickled fish bowl. That would get shad, fish roe, minnows, and chub more sellable in guild traders.