THE JUBILEE PHENONMENON

JUBILEE!!! The cry is eagerly awaited each summer by Mobile Bay residents. They are excited by the prospect of gigging hundreds of flounder or catching tubs of crabs in just a few hours.

On some occasions it’s primarily flounders that congregate and at other times it’s a “shrimp jubilee” or “crab jubilee” but generally all three species plus a few other fish and eels, are involved.

Jubilees may affect the entire Eastern Shore from Daphne to Mullet Point, a distance of about 15 miles. Or, they may be limited to only a few hundred feet of beach. The smaller, localized jubilees occur more often than the larger ones but are more difficult to locate. It is thought by many, that Jubilees of this magnitude occur only two places in the world, Tokyo Bay in Japan and right here in Mobile Bay.

For a jubilee to take place, a very specific set of conditions must exist. They usually only occur in the summer, usually in the morning before sunrise. The previous day’s weather conditions must include an overcast or cloudy day, a gentle wind from the east, and a calm and slick bay surface. Also, a rising tide is necessary; a change to a falling tide will stop the jubilee. It takes a combination of all these conditions to produce the phenomenon.

Jubilees are caused primarily by up-wellings or upward movement of oxygen-poor bottom waters forcing bottom-type fish and crustaceans ashore. Bottom water low in oxygen results from several coincidental circumstances, pockets of salty water accumulate in the deep parts of the northern portion of Mobile Bay stagnate during calm conditions. The stagnation is caused by salinity stratification, or layering effect, with the heavier salty Gulf water overlain by lighter, fresher river water. Stratification prevents movement of oxygen from the air into the bottom saline water.

These deep water pockets tend to collect plant matter washed into the Bay from the marshes and swamps upstream. As this vegetative matter decomposes, it provides food for the microorganisms in the water. An abundant food supply combined with the warm water temperature causes a population explosion. As these microorganisms grow and multiply, they consume tremendous quantities of oxygen. In this way, the bottom water becomes very low in oxygen-poor water remains in the deep pocket offshore.

Due to the lack of oxygen, these jubilee-affected fish and shellfish cannot carry out normal muscular activities, such as swimming. They move slowly and seem reluctant to swim even to escape capture. However, few fish or crustaceans die during jubilees, except for those caught by jubilee enthusiasts.

No one knows when or at what area on the beach the next jubilee will occur. Most summers there are several but you can’t even be sure of that!

*Information provided by the Auburn University Marine Extension & Research Center and Marriot’s Grand Hotel.