I believe bass get conditioned at times that spiny fish are less palatable and therefore often focus on other spineless prey when possible. I have raised bass of different species and sunfish in aquariums for many years. During those years I have tried feeding them all kinds of things. One thing I have observed is if it is something new and has spines or can nip back, say a crayfish for example. If that bass gets whacked by a crayfish, it can takes many many weeks for that bass to forget that experience and begin eating crayfish again. Especially if they have other food sources available. I can see this occurring in the wild as well. A bass goes to feed on a BG, gets a mouth full of spines and spits the BG out. It has now been conditioned. If there are shiners, shad or other species present to feed on, that bass will I am betting focus more on them...
I think the biggest proof that bass prefer shiners over BG is this little experiment. I have tried it before. In a controlled environment, say a large aquarium or outdoor koi pond have 5 or 10 bass. Then place 20 BG and 20 GSH of the same size into that pond or aquarium at the same time. See which ones are gone first... I'll bet my next paycheck the BG are around long after all the GSH have been eaten. You certainly can't say it's because BG are faster and more nimble as GSH have BG beat in both of those departments. It's those spines and bass would rather eat non spiny fish any day over spiny ones.
