Ostreidae
By Jeremy Trombley
Oysters are a common food resource and have been exploited in a variety of forms around the world for thousands of years. They are considered a delicacy in many cultures and are cultivated on a large scale throughout the world.
There are many varieties of oysters, all belonging to the family Ostreidae. They are bivalve mollusks that live in the ocean or brackish water. Their soft bodies are encased in a pair of calcified valves which form a shell. to protect them. They filter plankton from the surrounding water using gills and cilia, trapping the nutrients in mucous on the gills. In this way they filter several gallons of water every day, keeping it from becoming stagnant.
Vast oyster middens attest to the popularity of the mollusk as a food resource throughout history. In fact, they are among the earliest marine foods exploited by humans. Many different species of oyster exist around the world, however only a few are highly prized as food. In North America, the best known variety is the American Oyster (Crassostrea virginica). These may grow up to seven inches in length, so are much larger than European oysters, but are similar in size to the Portuguese variety. They are found along the eastern coast of North America from Canada to the Gulf of Mexico, but those that come from Cape Cod, Long Island and the Chesapeake bay are the most highly prized. It is believed that the oysters derive special flavors from the particular waters in which they developed.
American oysters were once extremely abundant – much to the delight of the early settlers to North America. However, their numbers have been in decline since the 19th century – going from 170 million pounds harvested in 1895 to only 50 million pounds in the later 20th century. Oysters may be cooked in a variety of ways – grilled, boiled, baked, etc. - but they are also commonly consumed raw. Indeed, raw oysters are considered a delicacy in many parts of the world. However, care must be taken because raw oysters may contain pathogens that can cause illness in humans. As a result, those with weakened immune systems should avoid oysters in this form. It used to be that oysters were only available along the coast, and, while they are still most common in these regions, improved refrigeration has made it possible to enjoy them inland as well. According to tradition, oysters should only be consumed in months that contain the letter 'R.' The exact reason for this legend is not known, but it has been suggested that it is because people would get sick from oysters that had not been properly refrigerated. However, there is no reason to suspect that oysters consumed in non 'r' containing months would be any more dangerous than those consumed in 'r' months. Also, the improved refrigeration mentioned above significantly reduces this concern.
Due to their declining wild populations, and increasing consumption of oysters, large scale farming of oysters has been adopted in many parts of the world. Oyster culture is not a new invention – Romans in Britain cultivated European oysters many centuries ago. Oyster spat (baby oysters ejected from the parent) is collected on pallets. After several months, they are removed and placed in basins to protect them from predators, and later they are “finished” in places like Cape Cod where they will acquire the desired characteristics.
Oysters, Oysters, Oysters! http://www.globalgourmet.com/food/egg/egg0298/oysters.html
Davidson, Alan. The Oxford Companion to Food 2nd Ed. 2nd ed. Oxford University Press, USA, 2006.