Alright, well I was considering making a side mod for it, but I don't think it's possible or at least I don't know how. The tmodloader coding for catching fishes only lets you change what fish you catch, instead of changing catch rates. The way my mod works is that, if you set a 50% chance of catching a fish, then as long as your fishing in the correct biome, you have a 50% * fishing power / 195 of changing your catch into that fish.
I could make it so that you can set a chance for those food fishes to becomea junk item or something else though, but I wont be able to do it until tmodloader updates for the 1.3.5 versions of Terraria.