I don't really fish too much in TS4 because there's no way to keep them fresh in your inventory for very long. I like to keep some of them for eating but that's really hard to do, especially if you are somewhere like the Hermit's place in Granite Falls or the Island in Selvadorada.
I guess it's okay if you are trying to complete a collection, using a few for fertilizer, or just skilling up, but otherwise it's a no go. As OP noticed, you seem to keep getting the same cheap fish over and over again no matter what bait you are using.