Found this for ya:
Mid to late spring the carp will either be still in pre-spawn, or will actually be beginning the spawning process. When they are actually spawning, they are nearly impossible to catch. Quite often they will find shallow, muddy areas with some sort of wood or weed structure. Reed beds, brush piles and logs will attract them, but you might as well not bother trying to catch them at this time. They pair off and begin a spawning ritual, ramming themselves against the objects, onto shore and often jumping out of the water in pairs. It is an interesting thing to watch, and it can drive you absolutely crazy if it is happening while you are fishing. Quite often you will see the biggest of the big carp jumping like this. At this point you will probably want to still look for the pre-spawn carp to bite. Carp do not feed during the actual spawn.