thumb|right|A Jubilee event at Weeks Bay [[The National Estuarine Research Reserve System|National Estuary Research Reserve showing the macroorganic density typical of the event. Pictured here are crabs, flounder, stingray, and an eel.]]

Jubilee is the name used locally for a natural phenomenon that occurs sporadically on the shores of Mobile Bay, a large body of water on Alabama's Gulf Coast. During a jubilee many species of crab and shrimp, as well as flounder, eels, and other demersal fish will leave deeper waters and swarm—in large numbers and very high density—in a specific, shallower coastal area of the bay. A jubilee is a celebrated event in Mobile Bay, and it attracts large crowds, many drawn by the promise of abundant and easy-to-catch seafood.

Although similar events have been reported in other bodies of water, Mobile Bay is the only place where the regular appearance of this phenomenon has been documented.

Descriptions

thumb|180px|right|[[U.S. Civil War|Civil War-era map of Mobile Bay]]

The Mobile Bay jubilee typically takes place at least annually, and sometimes several times per year; years without a jubilee have been recorded, but they are exceedingly rare. Many accounts of the jubilee exist, the oldest dating back to the 1860s. Most jubilees happen in the pre-dawn hours.

Author Archie Carr comments, "At a good jubilee you can quickly fill a washtub with shrimp. You can gig a hundred flounders and fill the back of your pickup truck a foot deep in crabs."

In addition, harvesting them is made considerably easier by the effect that the oxygen deprivation has on the animals. Their behavior has been described as "depressed and moribund",

thumb|180px|left|A [[Landsat image of Mobile Bay facing north-northeast]]

After researching the oral histories and journalistic records of past jubilees, measuring physical and meteorologic conditions, and taking biological and chemical measurements, Loesch concluded that accumulated organic material on the bay floor could, under a certain set of conditions, result in a rapid depletion of oxygen in parts of the bay, driving fish to the surface seeking oxygenated water. If wind direction, surface temperature, salinity, and tidal variation interact in ways that allow or promote a jubilee, the situation can develop rather quickly. May sums up the mechanism of action thus:

In an oral account from 1960 a local fishing captain named Frank Phillips stated that he had observed jubilee events for the previous 60 years, indicating that "[N]either [the] frequency nor intensity ... had changed". He also stated that his father had also seen jubilee events "...during all his life."

  1. Jubilees occur only in the summer.
  2. They usually occur in early morning hours, i.e., before sunrise.
  3. The wind on the day previous and during the jubilee is from some easterly direction. If wind direction changes, the jubilee will cease.
  4. There is a rising tide during a jubilee; a change to falling will stop the jubilee.
  5. There are two water masses meeting, with the saltier water invading during a jubilee.

Jubilee in local culture

The length of coast that serves as the most popular jubilee grounds is densely populated.