Oyster farming is an aquaculture (or mariculture) practice in which oysters are bred and raised mainly for their pearls, shells and inner organ tissue, which is eaten. Oyster farming was practiced by the ancient Romans as early as the 1st century BC on the Italian Peninsula For more on these early efforts, see Sergius Orata. and later in Britain for export to Rome. The French oyster industry has relied on aquacultured oysters since the late 18th century.
History
Oyster farming was practiced by the ancient Romans as early as the 1st century BC on the Italian peninsula. With the Barbarian invasions the oyster farming in the Mediterranean and the Atlantic came to an end.
In fact, the Romans were the very first to cultivate Oysters. The Roman engineer Sergius Orata is known for his innovative ways of breeding and commercializing oysters. He did this by cultivating the mollusk with a system that could control the water levels.
In 1852 Monsieur de Bon started to re-seed the oyster beds by collecting the oyster spawn using makeshift catchers. An important step to the modern oyster farming was the oyster farm built by Hyacinthe Boeuf in the Ile de Ré. After obtaining the rights to a part of the coast he built a wall to make a reservoir and to break the strength of the current. Some time later the wall was covered with spat coming spontaneously from the sea which gave 2000 baby oysters per square metre.
The Ancient Romans started farming the Thames Estuary in Hampton-On-Sea, or Kent, England from the 1st Century to approximately the 4th Century. They would export the oysters back to Rome and throughout the Roman Empire. On July 25, 1864, The Herne Bay Hampton and Recuiver Oyster Fishery Company moved into the area to start oyster farming. In the 1870s the oyster trade suffered from overfishing and sent the industry into a decline. This caused the government of the United Kingdom to pass the 1877 Act to solve the problem. This act prevented the sale of dredged oysters from the months of June through August, and freshwater pond oyster sales from between May and August. A couple of years later the company closed its doors and all the assets were sold by 1881, closing the oyster farming in the Thames Estuary area in England.
Another place in England that is famous for its oyster fishing is Whitstable. The area's "kentish flats" have been used since the Romans started. The oysters would get shipped to Italy, where Roman Emperors would pay for them by their weight in gold.
Outside Europe, oysters were also a prized ingredient in China. Notably, Teng pioneers settling along the coast of Laufaushan obtained the right from the Chinese government to collect rent on the oyster beds established there from 1667 to 1909. Due to the Cantonese ethnozoological system classifying oysters as a plant, the commodity remained Laufaushan's primary product during recessions and religious observances prescribing vegetarianism. One of the primary drivers of oyster demand was oyster sauce. Supposedly discovered on accident by Lee Kum Sheung (founder of the brand Lee Kum Kee) in 1888, the product has gone on to become a staple of Cantonese cuisine that is accessible worldwide.
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
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.
The first step to cultivating oysters is conditioning broodstock. Broodstock are the "parent" oysters that will provide gametes for larvae. Oysters in the wild are only "ripe" with gametes for a short window. All of the oysters in an area will spawn at the same time to increase the chances that their gametes meet and fertile larvae are produced. To ensure ripe oysters for spawning throughout the season, some growers choose to keep mature oysters in a separate system where the farmer can manipulate the temperature and food within the system. While a recirculating system can be used, a flow-through system is generally better because the natural diversity of phytoplankton is a better diet for conditioning oysters. By setting up this separate system, the farmer can mimic the transition from winter to summer quicker than real-time, and essentially convince the oyster that it is time to spawn whenever the farmer needs more larvae.
When the farmer actually wants to spawn the oysters, they will put a batch of oysters in a tray and rapidly heat and cool the water to induce spawning. It is important to have a large number of oysters, because it is impossible to tell if an oyster is male or female from its outer appearance. Once the oysters start to spawn they can be picked up and placed into their own separate containers until they have released all of their gametes. Eggs and sperm can then be mixed together to fertilize.
Larvae tanks should be cleaned and disinfected before putting water in the tanks. Water quality should be tailored for the particular species, but most larvae will generally grow faster in warmer water. After the fertilized eggs and beginning-stage larvae have been added to the tank, they should be fed filtered or cultured algae daily, and have their water changed every-other day. This ensures no pathogens or foreign organisms enter the system and compete with or eat the larvae, and their water quality stays pristine to encourage growth. This is the most fragile stage of an oyster's life history.
After about two weeks an oyster will be ready to set. They will develop a small, round discoloration called an eyespot despite not being used for seeing. Their muscular foot will be visible under a microscope. At this point, the larvae can be put in a system with a variety of cultch options. The best cultch is usually full or ground up oyster shell because oysters are naturally attracted to other oyster shell to ensure their future reproductive success. After the larvae settle, they are considered "spat."
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 "cultch" (also spelled "cutch" or "culch"). 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.
In the third method the spat or seed are placed in a cultch 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. The Pacific oyster M. gigas is the species most commonly used with this type of farming.
Boats During the nineteenth century in the United States, various shallow draft sailboat designs were developed for oystering in the Chesapeake Bay. These included the bugeye, log canoe, pungy, sharpie and skipjack. During the 1880s, a powerboat called the Chesapeake Bay deadrise was also developed.
Since 1977, several boat builders in Brittany have built specialized amphibious vehicles for use in the area's mussel and oyster farming industries. The boats are made of aluminium, are relatively flat-bottomed, and have three, four, or six wheels, depending on the size of the boat. When the tide is out the boats can run on the tidal flats using their wheels. When the tide is in, they use a propeller to move themselves through the water. Oyster farmers in Jersey make use of similar boats.
Environmental impact While oysters themselves can be very beneficial to their environment, the farming of oysters and other shellfish is not necessarily restorative environmentally. However, it does hold promise for relieving pressure on land-based protein sources."The Case for Fish and Oyster Farming ," Carl Marziali, University of Southern California, May 17, 2009. Production of land-based protein sources can be detrimental to the earth environment as they generate a significant amount of greenhouse gases. Oysters, however, produce little to no greenhouse gases, and the difference in emissions between wild oysters and farmed oysters is negligible. The oysters themselves do not produce any methane, one of the most potent greenhouse gases, and just a very minimal amount of nitrous oxide and carbon dioxide. Restoration of oyster populations is encouraged for the ecosystem services they provide, including water quality maintenance, shoreline protection and sediment stabilization, nutrient cycling and sequestration, and habitat for other organisms.
There has been a decline in oyster population due to extensive factors such as climate change and overharvesting of wild populations. Because of this, oyster reef restoration has been significant in the past decades, and a native Olympia oyster restoration project has been implemented in Liberty Bay, Washington. This project uses a "Habitat Sustainability Index (HSI)" to assess the ecological impacts of the restoration. The HSI also measures the benefit to the oyster population as well. Oyster farming in the Chesapeake Bay has minimal or even positive impacts on the surrounding environment, and numerous oyster restoration projects are underway in the Chesapeake Bay. The Chesapeake Bay Foundation started working in conjunction with the Smithsonian Institution in 2022 to revive the oyster population that was disrupted due to the poor health of the water quality. In the U.S., Delaware is the only East Coast state without oyster aquaculture, but making aquaculture a state-controlled industry of leasing water by the acre for commercial harvesting of shellfish is being considered. Recreational oyster harvesting is strictly prohibited to protect both the threatened oysters and to protect people from potential disease. Bycatch reduction devices are required and violation results in a small fine. Supporters of Delaware's legislation to allow aquaculture cite: revenue, job creation, and nutrient cycling as the benefits. For example, It is estimated that one acre can produce nearly 750,000 oysters, which could filter between 15 and 40 million gallons of water daily. This is extremely beneficial to the marine ecosystem because the oysters feed on particulate matter and nitrogen, often from anthropogenic sources. This, in turn, reduces the algae growth and leads to an overall cleaner marine environment.