Oysters get even better in cooler weather

Special to The Star
Published: Thursday, December 5, 2013 at 09:35 AM.

By Tom Baird


If you like oysters, this is a great time of year. Many people say that oysters are at their most delicious in cool weather months and when harvested from cold water. We are all familiar with oysters, those tasty, ugly mollusks whose harvest supports a significant portion of the livelihood and economy of our neighbors in Franklin County. We are all familiar with the water wars between Alabama, Georgia and Florida and the effect of the diminished natural flow of the Chattahoochee- Flint–Apalachicola river system on the ecology of Apalachicola Bay. We condemn the lack of water conservation efforts of metropolitan Atlanta, the bureaucracy of the Corps of Engineers, the massive loss of water to evaporation behind multiple dams on the rivers, and sympathize with hardworking oystermen and their families for the loss of productivity of Apalachicola Bay. (Historically, Franklin County harvests more than 90 percent of Florida’s oysters and 10 percent of the nationwide supply). Yet as we enjoy a plate of chilled raw oysters, or a platter of delectable fried oysters, do we ever consider the importance of the oyster to the economy of the sea?

Oysters (Crassostrea virginica) create a mollusk reef or oyster reef. These oyster bars or “beds” become a haven for other sea life and retain nutrients on which the whole system depends. Oysters are filter feeders. Once attached to a suitable object, they consume material and planktonic organisms suspended in the water column and are nonselective. The most important foods to oysters are microscopic algae cells, bacteria and detritus - decomposing organic matter. For this reason, oysters are easily contaminated by pollutants in the water because they concentrate them as they feed.

In Florida, a marketable oyster is generally two to three years old, however, under good conditions, an Apalachicola Bay oyster can be of marketable size in less than two years. To grow best, oysters need a good water flow, proper salinity and temperature and, of course, a suitable place of attachment. Good circulation not only aids in dispersing their larvae to new locations, but assures wastes are carried away and plenty of nutrients brought to their door.

Oysters tolerate a wide range of salinities, but permanent communities do best in a range of 10 – 20 parts per thousand. (Open Gulf salinity is about 35 – 36 parts per thousand.)  Since St. Joseph Bay is highly saline (there is little freshwater input), we don’t have oyster reefs in the bay. Live oysters can be found in St. Joseph Bay however, usually attached to an old wooden piling and mainly in the southeast corner of the bay where there is occasional freshwater input. Apalachicola Bay is ideal with freshwater input from Florida’s largest river. Oysters also have wide temperature tolerances, but best growth occurs between 77-79 degrees Fahrenheit.

Oysters spawn during warm months in Florida, generally from April through October and individuals may spawn several times during a season. The advent of warm water temperatures will stimulate a few oysters to spawn. This in turn triggers spawning in the rest, maximizing the number of egg and sperm in the water and the likelihood of fertilization. The fertilized egg develops into a larva that drifts in the current for two to three weeks. Settling and attachment occurs when mature larvae contact a suitable hard object, like a seawall, old boat hull, piling, or another oyster. The larvae, called spat, will readily attach to other oyster shells and soon an oyster clump grows into an oyster reef or oyster bar. Oyster bars grow perpendicular to the direction of the current. The resulting dam enables oysters to filter food from the flowing water more efficiently.

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