No one knows what causes a jubilee. One theory revolves around oxygen depletion caused by decay of organic material settling on the bottom of the bay, a process that is accelerated during the summer. Coupled with certain climatic conditions, this is believed to drive the crabs, shrimp and fish (particularly the bottom dwelling ones) toward the shore in a desperate search for more oxygen-rich water.
Jubilees cannot be predicted with certainty. Local folklore offers some clues for telling when one might be in the offing: The water is calm the day before and during the event itself, the wind is gentle and blowing from the east, the tide is rising, and the sky is cloudy or overcast. Not all of these conditions must be present before a jubilee can occur, though, nor does the presence of all of them at once guarantee a jubilee. To the residents of Mobile Bay's eastern shore, the jubilee remains as a mysterious -- and most welcomed -- gift from nature.