Kingfish, in a lake that large there are is no doubt at least one feeder creek which in my opinion is a ready made highway for native crayfish/mudbugs to find it by. If your lake had the proper habitat they would already be present if they aren't already and you just aren't see them. Have you walked the edge at night with a spotlight and shined it into shallow areas near rocks, legs etc? You may be surprised at what you see...