I don't really know if bait is more scattered on cloudy days or not. From my experience, the fish are generally more active on cloudy days. Sunny, blue sky days seem to result in slower trips for me. Especially if there is no wind. This is especially the case from my experience perch fishing. Crappie fishing it seems the fish are shallower in the water column on cloudy days or low light conditions. Sun drives the fish deeper and to cover. Not really an answer to your question but a few thoughts.