The Nature Conservancy. Protecting nature. Preserving life.™

Over the past few years, the Conservancy in Mississippi has been working with partners on oyster reef restoration work. © Nicole Vickery/The Nature Conservancy

Ecological Significance, History and Range

Mississippi’s coastal region provides habitat for migratory birds and waterfowl as well as for shrimp, crabs and fish that fuel the local economy and provide recreational opportunities.

Critical to the overall health of this rich ecosystem are oyster reefs, which provide important habitat for aquatic species and help improve water quality by removing excess nutrients that enter the Gulf through freshwater sources. Reefs also provide protection against coastal erosion and storm surges.

The American oyster lives in shallow water in estuaries and behind barrier islands. Although populations have declined considerably over several decades, they are found most abundantly along the coast of the Gulf of Mexico.

Along the East Coast of the United States, American oysters are found from Canada south to the Florida Keys.

The first-ever global analysis of shellfish reefs, which was released by the Conservancy in 2009, estimates that up to 89 percent of the oyster reefs in the Gulf of Mexico have disappeared.

While the report listed the state of oyster reefs in the Gulf of Mexico as “fair,” the report rated most shellfish regions globally much worse – in many cases they have disappeared altogether.

Threats

Overfishing, dredging, habitat loss and the deterioration of water quality have decimated much of the Gulf’s oyster reefs.

Characteristics

American oysters...

• feed by opening their shells and pumping water through their gills to filter out plankton and other particles;
• adults can filter up to a half gallon of water per hour;
• spawn from March through November in the northern Gulf of Mexico; each female produces 23-86 millions eggs per spawning, and they can spawn several times in one season;
• eggs, once fertilized, develop into larvae within 24 hours and remain suspended for two to three weeks, after which time they “crawl” in search of a solid surface for attachment. Oysters prefer to attach to other oyster shells.
• Female oysters can spawn as soon as four weeks after attachment
• About 70 percent of the nation’s total landings of oysters come from the Gulf of Mexico.