if i catch a small nongame fish, and kill it can i use the whole fish for bait?

Yes, you can. Bait is defined as Organic substances, other than rubber, wood feather, fiber, or plastic, attached to a hook to attract fish. Bait includes insects, insect larvae, worms, dead fish, fish parts, any other animal or vegetable matter, or scented synthetic materials. Note: Use of live fish , leeches, frogs, salamanders, waterdogs or shrimp as bait is prohibited in Idaho, except that live crayfish may be used if caught on the body of water being fished.