The size of hooks to use for live shrimp really depends on what you are going after and also where you are planning on hooking them. I tend to target speckle trout and blackfish when using live shrimp, although my setup for each varies slightly. I like to run a thinner fluorocarbon leader, maybe 12-15lb at most to the smallest hook I can get away with. The smaller the hook the less weight on the shrimp and the more it will be able to move around. Also it matters where you hook them, I usually place it right at the base of the horn, lets em stay alive a lot longer and they have the full ability to use the rest of their body to do what they do. I personally like the owner tournament legal circle hooks for trout, the smaller the better.