Oyster farming

Harvesting oysters from the pier at Cancale, Brittany, France 2005

Oyster farming is an aquaculture (or mariculture) practice in which oysters are raised for human consumption. Oyster farming most likely developed in tandem with pearl farming, a similar practice in which oysters are farmed for the purpose of developing pearls. It was practiced by the ancient Romans as early as the 1st century BC on the Italian peninsula^[1] and later in Britain for export to Rome. The French oyster industry has relied on aquacultured oysters since the late 18th century.^[2]

Varieties of farmed oysters

Commonly farmed food oysters include the Eastern oyster Crassostrea virginica, the Pacific oyster Crassostrea gigas, Belon oyster Ostrea edulis, the Sydney rock oyster Saccostrea glomerata, and the Southern mud oyster Ostrea angasi.

Cultivation

Oyster farming boats in Morbihan (Brittany, France)

Oysters naturally grow in estuarine bodies of brackish water. When farmed, the temperature and salinity of the water are controlled (or at least monitored), so as to induce spawning and fertilization, as well as to speed the rate of maturation – which can take several years.

Three methods of cultivation are commonly used. In each case oysters are cultivated to the size of "spat," the point at which they attach themselves to a substrate. The substrate is known as a "culch" or "cultch". The loose spat may be allowed to mature further to form "seed" oysters with small shells. In either case (spat or seed stage), they are then set out to mature. The maturation technique is where the cultivation method choice is made.

In one method the spat or seed oysters are distributed over existing oyster beds and left to mature naturally. Such oysters will then be collected using the methods for fishing wild oysters, such as dredging.

In the second method the spat or seed may be put in racks, bags, or cages(or they may be glued in threes to vertical ropes) which are held above the bottom. Oysters cultivated in this manner may be harvested by lifting the bags or racks to the surface and removing mature oysters, or simply retrieving the larger oysters when the enclosure is exposed at low tide. The latter method may avoid losses to some predators, but is more expensive.^[3]

In the third method the spat or seed are placed in a culch within an artificial maturation tank. The maturation tank may be fed with water that has been especially prepared for the purpose of accelerating the growth rate of the oysters. In particular the temperature and salinity of the water may be altered somewhat from nearby ocean water. The carbonate minerals calcite and aragonite in the water may help oysters develop their shells faster and may also be included in the water processing prior to introduction to the tanks. This latter cultivation technique may be the least susceptible to predators and poaching, but is the most expensive to build and to operate.^[4] The Pacific oyster C. gigas is the species most commonly used with this type of farming.

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  Oyster harvesting using rakes (top) and sail driven dredges (bottom). From L'Encyclpédie of 1771

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  Oyster culture using tiles as culch. Taken from The Illustrated London News 1881

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  Department of Gironde (33) - Andernos-les-Bains, little boats of the oyster culturists (circa 1920)

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  Harvesting oysters by hand on Willapa Bay, Washington, USA in October 1969

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  Purpose made oyster baskets

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  Working on oysters at Belon, Brittany, France 2005

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  Oyster farm on Prince Edward Island Canada

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  Oyster farm in South Australia

Environmental Impact

The farming of oysters and other shellfish is relatively benign or even restorative environmentally, and holds promise for relieving pressure on land-based protein sources.^[5]

Predators, diseases and pests

Oyster predators include starfish, oyster drill snails, stingrays, Florida stone crabs, birds, such as oystercatchers and gulls, as well as humans.

Diseases that can affect either farmed C. virginica or C. gigas oysters include Perkinsus marinus (Dermo) and Haplosporidium nelsoni (MSX). However, C. viginicus are much more susceptible to Dermo or MSX infections than are the C. gigas species of oyster.^[6] Pathogens of O. edulis oysters include Marteilia refringens and Bonamia ostrea.^[7] In the north Atlantic Ocean, oyster crabs may live in an endosymbiotic commensal relationship within a host oyster. Since oyster crabs are considered a food delicacy they may not be removed from young farmed oysters, as they can themselves be harvested for sale.

Polydorid polychaetes are known as pests of cultured oysters.^[8]

See also

• Gathering seafood by hand
• Oyster pirate
• Oystering machinery

Nineteenth century shallow draft sailboats designed primarily for oystering include:

• Bugeye
• Log canoe
• Pungy
• Sharpie
• Skipjack

Also, from the 1880s on, the powerboat known as the Chesapeake Bay deadrise was a hull type used for oystering in the Chesapeake Bay of the United States.

References

1. ^ James Arnold Higginbotham, Piscinae: artificial fishponds in Roman Italy (University of North Carolina Press, 1997), p. 247, note 44 online; Cynthia J. Bannon, "Servitudes for Water Use in the Roman Suburbium," Historia 50 (2001), pp. 47–50. For more on these early efforts, see Sergius Orata.
2. ^ Kurlansky, pg. 49
3. ^ "Oyster Farming in Louisiana" (PDF). Louisiana State University. http://www.lamer.lsu.edu/classroom/edonahalfshell/pdf/cycle_info.pdf. Retrieved 2008-01-16. 
4. ^ "Korea-Us Aquaculture". http://www.lib.noaa.gov/korea/main_species/pacific.htm. Retrieved 2008-08-08. 
5. ^ "The Case for Fish and Oyster Farming," Carl Marziali, University of Southern California, May 17, 2009.
6. ^ Goedken, Michael; Brenda Morsey, Inke Sunila, Sylvain De Guise (August 2005). "Immunomodulation of Crassostrea gigas and Crassostrea virginica cellular defense mechanisms by Perkinsus marinus". Journal of Shellfisheries Research. http://findarticles.com/p/articles/mi_m0QPU/is_2_24/ai_n15384489. 
7. ^ "FAO Fisheries & Aquaculture Ostrea edulis". FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS. http://www.fao.org/fishery/culturedspecies/Ostrea_edulis. Retrieved 2008-08-06. 
8. ^ Simon, C.A. 2011. Polydora and Dipolydora (Polychaeta: Spionidae) associated with molluscs on the south coast of South Africa, with descriptions of two new species. African Invertebrates 52 (1): 39-50.[1]

Further reading

• Kurlansky, Mark (2006). The Big Oyster: History on the Half Shell. New York: Ballantine Books. ISBN 978-0345476388.