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Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estu ...
habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not all oysters are in the superfamily
Ostreoidea Ostreoidea is a taxonomic superfamily of bivalve marine mollusc, sometimes simply identified as oysters, containing two families. The ostreoids are characterized in part by the presence of a well developed axial rod. Anal flaps are known ...
. Some types of oysters are commonly consumed (cooked or raw), and in some locales are regarded as a
delicacy A delicacy is usually a rare and expensive food item that is considered highly desirable, sophisticated, or peculiarly distinctive within a given culture. Irrespective of local preferences, such a label is typically pervasive throughout a r ...
. Some types of
pearl oyster ''Pinctada'' is a genus of saltwater oysters, marine bivalve mollusks in the family Pteriidae. These pearl oysters have a strong inner shell layer composed of nacre, also known as "mother of pearl". Pearl oysters are not closely related to e ...
s are harvested for the
pearl A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle) of a living shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pearl is composed of calcium carb ...
produced within the mantle.
Windowpane oyster The windowpane oyster (''Placuna placenta'') is a bivalve marine mollusk in the family of Placunidae. They are edible, but valued more for their shells (and the rather small pearls). The shells have been used for thousands of years as a glass su ...
s are harvested for their translucent shells, which are used to make various kinds of decorative objects.


Etymology

The word ''oyster'' comes from
Old French Old French (, , ; Modern French: ) was the language spoken in most of the northern half of France from approximately the 8th to the 14th centuries. Rather than a unified language, Old French was a linkage of Romance dialects, mutually intellig ...
, and first appeared in English during the 14th century. The French derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
, the feminine form of , which is the latinisation of the
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
() 'oyster'. Compare () 'bone'.


Types


True oysters

True oyster The Ostreidae, the true oysters, include most species of molluscs commonly consumed as oysters. Pearl oysters are not true oysters, and belong to the order Pteriida. Like scallops, true oysters have a central adductor muscle, which means the s ...
s are members of the family
Ostreidae The Ostreidae, the true oysters, include most species of molluscs commonly consumed as oysters. Pearl oysters are not true oysters, and belong to the order Pteriida. Like scallops, true oysters have a central adductor muscle, which means the ...
. This family includes the edible oysters, which mainly belong to the genera ''
Ostrea ''Ostrea'' is a genus of edible oysters, marine bivalve mollusks in the family Ostreidae, the oysters. Fossil records This genus is very ancient. It is known in the fossil records from the Permian to the Quaternary (age range: from 259 to 0. ...
'', ''
Crassostrea ''Crassostrea'' is a genus of true oysters (family Ostreidae) containing some of the most important oysters used for food. Some species in the genus have been moved to the genus '' Magallana''. Species Extant species Extant species include:< ...
'', ''
Ostreola ''Ostreola'' is a genus of fungi in the family Mytilinidiaceae. This is a monotypic genus, containing the single species ''Ostreola consociata''. ''Ostreola'' may also be used to refer to also a genus of oyster in the family Ostreidae; however, ...
'', ''
Magallana ''Magallana'' is a genus of true oysters (family Ostreidae) containing some of the most important oysters used for food. Species in this genus have been moved from ''Crassostrea'' after it was found to be paraphyletic. Species Extant species ...
'', and ''
Saccostrea Rock oysters are true oysters of the genus ''Saccostrea'', belonging to the subfamily Saccostreinae of the family Ostreidae . MolluscaBase eds. (2022). MolluscaBase. Saccostrea Dollfus & Dautzenberg, 1920. Accessed through: World Register of ...
''. Examples include the
European flat oyster European, or Europeans, or Europeneans, may refer to: In general * ''European'', an adjective referring to something of, from, or related to Europe ** Ethnic groups in Europe ** Demographics of Europe ** European cuisine, the cuisines of Europe a ...
,
eastern oyster The eastern oyster (''Crassostrea virginica'')—also called the Atlantic oyster, American oyster, or East Coast oyster—is a species of true oyster native to eastern North and South America. Other names in local or culinary use include the We ...
,
Olympia oyster ''Ostrea lurida'', common name the Olympia oyster, after Olympia, Washington in the Puget Sound area, is a species of edible oyster, a marine bivalve mollusk in the family Ostreidae. This species occurs on the northern Pacific coast of North A ...
,
Pacific oyster The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand. Etymology The genus ''Mag ...
, and the Sydney rock oyster. Ostreidae evolved in the
Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...
epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...
: The
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
'' Liostrea'' grew on the shells of living
ammonoids Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
.


Pearl oysters

Almost all shell-bearing mollusks can secrete pearls, yet most are not very valuable. Pearls can form in both saltwater and freshwater environments.
Pearl oyster ''Pinctada'' is a genus of saltwater oysters, marine bivalve mollusks in the family Pteriidae. These pearl oysters have a strong inner shell layer composed of nacre, also known as "mother of pearl". Pearl oysters are not closely related to e ...
s are not closely related to true oysters, being members of a distinct family, the feathered oysters (
Pteriidae Pteriidae, also called the feather oysters, is a family of medium-sized to large saltwater clams. They are pearl oysters, marine bivalve molluscs in the order Pteriida. Some of the species in this family are important economically as the sou ...
). Both cultured pearls and natural pearls can be extracted from pearl oysters, though other molluscs, such as the freshwater mussels, also yield pearls of commercial value. The largest pearl-bearing oyster is the marine ''Pinctada maxima'', which is roughly the size of a dinner plate. Not all individual oysters produce pearls naturally. In nature, pearl oysters produce pearls by covering a minute invasive object with nacre. Over the years, the irritating object is covered with enough layers of nacre to become a pearl. The many different types, colours and shapes of pearls depend on the natural
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...
of the nacre, and the shape of the original irritant. Pearl farmers can culture a pearl by placing a nucleus, usually a piece of polished mussel shell, inside the oyster. In three to seven years, the oyster can produce a perfect pearl. Since the beginning of the 20th century, when several researchers discovered how to produce artificial pearls, the cultured pearl market has far outgrown the natural pearl market.


Other types

A number of bivalve molluscs (other than true oysters and pearl oysters) also have common names that include the word "oyster", usually because they either taste like or look somewhat like true oysters, or because they yield noticeable pearls. Examples include: *
Thorny oyster ''Spondylus'' is a genus of bivalve molluscs, the only genus in the family Spondylidae.MolluscaBase (2019). MolluscaBase. Spondylus Linnaeus, 1758. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=t ...
s in the genus ''Spondylus'' *Pilgrim oyster, another term for a scallop, in reference to the scallop shell of St. James *
Saddle oyster Anomiidae is a family of saltwater clams, marine bivalve molluscs related to scallops and oysters, and known as anomiids. It contains seven genera. The family is known by several common names, including jingle shells, mermaid's toenails, and sa ...
s, members of the
Anomiidae Anomiidae is a family of saltwater clams, marine bivalve molluscs related to scallops and oysters, and known as anomiids. It contains seven genera. The family is known by several common names, including jingle shells, mermaid's toenails, and sa ...
family also known as jingle shells * Dimydarian oysters, members of the family Dimyidae *
Windowpane oyster The windowpane oyster (''Placuna placenta'') is a bivalve marine mollusk in the family of Placunidae. They are edible, but valued more for their shells (and the rather small pearls). The shells have been used for thousands of years as a glass su ...
s File:Crassostrea_gigas_p1040847.jpg,
Pacific oyster The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand. Etymology The genus ''Mag ...
File:Ostrea edulis Marennes p1050142.jpg,
Pacific oyster The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand. Etymology The genus ''Mag ...
, opened
In the
Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...
, a local thorny oyster species known as Tikod amo is a favorite seafood source in the southern part of the country. Because of its good flavor, it commands high prices.


Anatomy

Oysters breathe primarily via gills. In addition to their gills, oysters can exchange gases across their mantles, which are lined with many small, thin-walled blood vessels. A small, three-chambered
heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...
, lying under the adductor muscle, pumps colorless
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
to all parts of the body. At the same time, two
kidneys The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...
, located on the underside of the muscle, remove waste products from the blood. Their nervous system includes two pairs of nerve cords and three pairs of ganglia. There is no evidence that oysters have a brain. While some oysters have two sexes (European oyster and Olympia oyster), their reproductive organs contain both eggs and sperm. Because of this, it is technically possible for an oyster to fertilize its own eggs. The
gonads A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...
surround the digestive organs, and are made up of sex cells, branching tubules, and connective tissue. Once her millions of eggs are fertilized, the female discharges them into the water. The larvae develop in about six hours and exist suspended in the water column as veliger larvae for two to three weeks before settling on a bed and reaching sexual maturity within a year.


Feeding

Oysters are filter feeders, drawing water in over their
gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
s through the beating of cilia. Suspended
plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
and non-food particles are trapped in the
mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
of a gill, and from there are transported to the mouth, where they are eaten, digested, and expelled as feces or pseudofeces that fall to the bottom and remain out of the water column. Oysters feed most actively at temperatures ranging from the high 60s to the high 70s (). Under ideal laboratory conditions, an oyster can filter up to of water per day. Under average conditions, mature oysters filter .
Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / ...
's once-flourishing oyster population historically filtered excess nutrients from the estuary's entire water volume every three to four days. As of 2008 it was estimated that a complete cycle would take nearly a year.


Habitat and behaviour

A group of oysters is commonly called a bed or
oyster reef The term ''oyster reef'' refers to dense aggregations of oysters that form large colonial communities. Because oyster larvae need to settle on hard substrates, new oyster reefs may form on stone or other hard marine debris. Eventually the oyster ...
. As a keystone species, oysters provide
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
for many marine species. ''Crassostrea'' and ''Saccostrea'' live mainly in the intertidal zone, while ''Ostrea'' is
subtidal The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...
. The hard surfaces of oyster shells and the nooks between the shells provide places where a host of small animals can live. Hundreds of animals, such as
sea anemones Sea anemones are a group of predatory marine invertebrates of the order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classified in the phylum Cnidaria, ...
,
barnacles A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...
, and hooked mussels, inhabit
oyster reef The term ''oyster reef'' refers to dense aggregations of oysters that form large colonial communities. Because oyster larvae need to settle on hard substrates, new oyster reefs may form on stone or other hard marine debris. Eventually the oyster ...
s. Many of these animals are prey to larger animals, including fish, such as striped bass,
black drum The black drum (''Pogonias cromis''), also known as the drum or drummer, is a saltwater fish similar to its cousin, the red drum. It is in the genus '' Pogonias''. Though most specimens are generally found in the 5-30 lb (2–14 kg) ran ...
and
croakers Sciaenidae are a family of fish in the order Acanthuriformes. They are commonly called drums or croakers in reference to the repetitive throbbing or drumming sounds they make. The family consists of about 286 to 298 species in about 66 to 70 gene ...
. An oyster reef can increase the surface area of a flat bottom 50-fold. An oyster's mature shape often depends on the type of bottom to which it is originally attached, but it always orients itself with its outer, flared shell tilted upward. One valve is cupped and the other is flat. Oysters usually reach maturity in one year. They are protandric; during their first year, they spawn as males by releasing sperm into the water. As they grow over the next two or three years and develop greater energy reserves, they spawn as females by releasing
eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
. Bay oysters usually spawn from the end of June until mid-August. An increase in water temperature prompts a few oysters to spawn. This triggers spawning in the rest, clouding the water with millions of eggs and sperm. A single female oyster can produce up to 100 million eggs annually. The eggs become fertilized in the water and develop into larvae, which eventually find suitable sites, such as another oyster's shell, on which to settle. Attached oyster larvae are called spat. Spat are oysters less than long. Many species of bivalves, oysters included, seem to be stimulated to settle near adult
conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organis ...
s. Oysters filter large amounts of water to feed and breathe (exchange and with water) but they are not permanently open. They regularly shut their valves to enter a resting state, even when they are permanently submersed. Their behaviour follows very strict circatidal and circadian rhythms according to the relative moon and sun positions. During neap tides, they exhibit much longer closing periods than during the spring tide. Some tropical oysters, such as the
mangrove oyster Mangrove oyster is a common name for several oysters that live on mangrove roots and may refer to: *'' Crassostrea rhizophorae'' *'' Crassostrea tulipa'' *' {{Animal common name Mollusc common names ...
in the family
Ostreidae The Ostreidae, the true oysters, include most species of molluscs commonly consumed as oysters. Pearl oysters are not true oysters, and belong to the order Pteriida. Like scallops, true oysters have a central adductor muscle, which means the ...
, grow best on
mangrove A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...
roots. Low tide can expose them, making them easy to collect. The largest oyster-producing body of water in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
is the
Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / ...
, although these beds have decreased in number due to overfishing and pollution. Willapa Bay in Washington produces more oysters than any other estuary in the US. Other large
oyster farming 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 ...
areas in the US include the bays and estuaries along the coast of the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
from
Apalachicola, Florida Apalachicola ( ) is a city and the county seat of Franklin County, Florida, United States, on the shore of Apalachicola Bay, an inlet of the Gulf of Mexico. The population was 2,231 at the 2010 census. History The Apalachicola people, after ...
, in the east to Galveston, Texas, in the west. Large beds of edible oysters are also found in Japan and Australia. In 2005, China accounted for 80% of the global oyster harvest. In Europe, France remained the industry leader. Common oyster predators include crabs,
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
s, starfish, and
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
s. Some oysters contain crabs, known as
oyster crab The oyster crab (''Zaops ostreus'') is a small, whitish or translucent crab in the family Pinnotheridae. Ecology It is less than half an inch across, and lives inside the gills of an oyster or a clam. It uses the oyster for protection and live ...
s.


Nutrient cycling

Bivalves, including oysters, are effective filter feeders and can have large effects on the water columns in which they occur. As filter feeders, oysters remove plankton and organic particles from the water column. Multiple studies have shown individual oysters are capable of filtering up to of water per day, and thus oyster reefs can significantly improve water quality and clarity. Oysters consume nitrogen-containing compounds ( nitrates and
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
),
phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...
s, plankton, detritus, bacteria, and dissolved organic matter, removing them from the water. What is not used for animal growth is then expelled as solid waste pellets, which eventually decompose into the atmosphere as nitrogen. In
Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...
, the
Chesapeake Bay Program The Chesapeake Bay Program is the regional partnership that directs and conducts the restoration of the Chesapeake Bay in the United States. As a partnership, the Chesapeake Bay Program brings together members of various state, federal, academic a ...
had implemented a plan to use oysters to reduce the amount of nitrogen compounds entering the
Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / ...
by per year by 2010. Several studies have shown that oysters and
mussels Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which ...
have the capacity to dramatically alter nitrogen levels in estuaries. In the U.S.,
Delaware Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent Del ...
is the only East Coast state without aquaculture, but making aquaculture a state-controlled industry of leasing water by the acre for commercial harvesting of shellfish is being considered. Supporters of Delaware's legislation to allow oyster aquaculture cite revenue, job creation, and nutrient cycling benefits. It is estimated that can produce nearly 750,000 oysters, which could filter between of water daily. Also see
nutrient pollution Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or ...
for an extended explanation of nutrient remediation.


Ecosystem services

As an ecosystem engineer, oysters provide supporting
ecosystem services Ecosystem services are the many and varied benefits to humans provided by the natural environment and healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystem, grassland ecosystems, and aquatic ecosystems. ...
, along with provisioning, regulating and cultural services. Oysters influence
nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...
, water filtration, habitat structure,
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
, and
food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is consumer-resource system. Ecologists can broadly lump all life forms into one o ...
dynamics. Assimilation of nitrogen and phosphorus into shellfish tissues provides an opportunity to remove these nutrients from the water column. In California's
Tomales Bay Tomales Bay is a long, narrow inlet of the Pacific Ocean in Marin County in northern California in the United States. It is approximately long and averages nearly wide, effectively separating the Point Reyes Peninsula from the mainland of Mar ...
, native oyster presence is associated with higher species diversity of benthic invertebrates. The ecological and economic importance of oyster reefs has become more acknowledged, restoration efforts have increased.


Human history

Middens testify to the prehistoric importance of oysters as food, with some middens in
New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...
, Australia, dated at ten thousand years. They have been cultivated in Japan from at least 2000 BC. In the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
, the town of
Whitstable Whitstable () is a town on the north coast of Kent adjoining the convergence of the Swale Estuary and the Greater Thames Estuary in southeastern England, north of Canterbury and west of Herne Bay. The 2011 Census reported a population of ...
is noted for
oyster farming 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 ...
from beds on the
Kentish Flats Kentish may be used as a name: *Kentish Council is a local government area in Tasmania, Australia *Kentish Town is an area of north west London, England Kentish as a surname: *John Kentish (minister), 1768–1853 *John Kentish (tenor), 1910&nd ...
that have been used since
Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *'' Epistle to the Romans'', shortened to ''Romans'', a lette ...
times. The borough of
Colchester Colchester ( ) is a city in Essex, in the East of England. It had a population of 122,000 in 2011. The demonym is Colcestrian. Colchester occupies the site of Camulodunum, the first major city in Roman Britain and its first capital. Colch ...
holds an annual
Oyster Feast The Oyster Feast is the centrepiece of the annual civic calendar in the ancient borough of Colchester located in Essex in the East of England. The Colchester Natives The Colne oyster fishery dates to the Roman era. It was mentioned in the Domesd ...
each October, at which "Colchester Natives" (the native oyster, ''
Ostrea edulis ''Ostrea edulis'', commonly known as the European flat oyster, is a species of oyster native to Europe. In Britain and Ireland, regional names include Colchester native oyster, mud oyster, or edible oyster. In France, ''Ostrea edulis'' are known ...
'') are consumed. The
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
hosts several other annual oyster festivals; for example, Woburn Oyster Festival is held in September. In fact, in Victorian England, it was quite common for people to go to the pub and enjoy their favorite beer with some oysters. They quickly realized that the "rich, sweet, malty stouts" were great with the "briny, creamy oyster." Then Brewers found that oyster shells naturally clarify a beer and they started putting crushed oyster shells into their brews. The first known brewery to start this was in 1938 at the Hammerton Brewery in London. That is where the oyster stout was first started. The French seaside resort of
Cancale Cancale (; ; Gallo: ''Cauncall'') is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. It is known as the birthplace of Saint Jeanne Jugan. Population Inhabitants of Cancale are called ''Cancalais'' in French. T ...
in
Brittany Brittany (; french: link=no, Bretagne ; br, Breizh, or ; Gallo: ''Bertaèyn'' ) is a peninsula, historical country and cultural area in the west of modern France, covering the western part of what was known as Armorica during the period ...
is noted for its oysters, which also date from Roman times. Sergius Orata of the
Roman Republic The Roman Republic ( la, Res publica Romana ) was a form of government of Rome and the era of the classical Roman civilization when it was run through public representation of the Roman people. Beginning with the overthrow of the Roman Ki ...
is considered the first major merchant and cultivator of oysters. Using his considerable knowledge of
hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counte ...
s, he built a sophisticated cultivation system, including channels and locks, to control the tides. He was so famous for this, the Romans used to say he could breed oysters on the roof of his house. In the early 19th century, oysters were cheap and mainly eaten by the
working class The working class (or labouring class) comprises those engaged in manual-labour occupations or industrial work, who are remunerated via waged or salaried contracts. Working-class occupations (see also " Designation of workers by collar colo ...
. Throughout the 19th century, oyster beds in New York Harbor became the largest source of oysters worldwide. On any day in the late 19th century, six million oysters could be found on barges tied up along the city's waterfront. They were naturally quite popular in
New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the Un ...
, and helped initiate the city's restaurant trade. New York's oystermen became skilled cultivators of their beds, which provided employment for hundreds of workers and nutritious food for thousands. Eventually, rising demand exhausted many of the beds. To increase production, they introduced foreign species, which brought disease; effluent and increasing sedimentation from erosion destroyed most of the beds by the early 20th century. Oysters' popularity has put ever-increasing demands on wild oyster stocks. This scarcity increased prices, converting them from their original role as working-class food to their current status as an expensive
delicacy A delicacy is usually a rare and expensive food item that is considered highly desirable, sophisticated, or peculiarly distinctive within a given culture. Irrespective of local preferences, such a label is typically pervasive throughout a r ...
. In the United Kingdom, the native variety (''Ostrea edulis'') requires five years to mature and is protected by an
Act of Parliament Acts of Parliament, sometimes referred to as primary legislation, are texts of law passed by the Legislature, legislative body of a jurisdiction (often a parliament or council). In most countries with a parliamentary system of government, acts of ...
during the May-to-August spawning season. The current market is dominated by the larger
Pacific oyster The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand. Etymology The genus ''Mag ...
and rock oyster varieties which are farmed year-round.


Fishing from the wild

Oysters are harvested by simply gathering them from their beds. In very shallow waters, they can be gathered by hand or with small rakes. In somewhat deeper water, long-handled rakes or oyster
tongs Tongs are a type of tool used to grip and lift objects instead of holding them directly with hands. There are many forms of tongs adapted to their specific use. The first pair of tongs belongs to the Egyptians. Tongs likely started off as ...
are used to reach the beds. Patent tongs can be lowered on a line to reach beds that are too deep to reach directly. In all cases, the task is the same: the oysterman scrapes oysters into a pile, and then scoops them up with the rake or tongs. In some areas, a
scallop dredge A fishing dredge, also known as a scallop dredge or oyster dredge, is a kind of dredge which is towed along the bottom of the sea by a fishing boat in order to collect a targeted edible bottom-dwelling species. The gear is used to fish for scal ...
is used. This is a toothed bar attached to a chain bag. The dredge is towed through an oyster bed by a boat, picking up the oysters in its path. While dredges collect oysters more quickly, they heavily damage the beds, and their use is highly restricted. Until 1965,
Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...
limited dredging to
sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminolo ...
s, and even since then motor boats can be used only on certain days of the week. These regulations prompted the development of specialized
sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminolo ...
s (the
bugeye The bugeye is a type of sailboat developed in the Chesapeake Bay for oyster dredging. The predecessor of the skipjack, it was superseded by the latter as oyster harvests dropped. Origins Between 1820 and 1865, the state of Maryland banned th ...
and later the skipjack) for dredging. Similar laws were enacted in Connecticut before World War I and lasted until 1969. The laws restricted the harvesting of oysters in state-owned beds to vessels under sail. These laws prompted the construction of the oyster sloop-style vessel to last well into the 20th century. ''Hope'' is believed to be the last-built Connecticut oyster sloop, completed in 1948. Oysters can also be collected by
divers Diver or divers may refer to: *Diving (sport), the sport of performing acrobatics while jumping or falling into water *Practitioner of underwater diving, including: **scuba diving, **freediving, **surface-supplied diving, **saturation diving, a ...
. In any case, when the oysters are collected, they are sorted to eliminate dead animals, bycatch (unwanted catch), and debris. Then they are taken to market, where they are either canned or sold live.


Cultivation

Oysters have been cultured since at least the days of the
Roman Empire The Roman Empire ( la, Imperium Romanum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn Rhōmaíōn) was the post- Republican period of ancient Rome. As a polity, it included large territorial holdings around the Mediter ...
. The
Pacific oyster The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand. Etymology The genus ''Mag ...
(''Magallana gigas'') is presently the most widely grown bivalve around the world. Two methods are commonly used, release and bagging. In both cases, oysters are cultivated onshore to the size of spat, when they can attach themselves to a substrate. They may be allowed to mature further to form "seed oysters". In either case, they are then placed in the water to mature. The release technique involves distributing the spat throughout existing oyster beds, allowing them to mature naturally to be collected like wild oysters. Bagging has the cultivator putting spat in racks or bags and keeping them above the bottom. Harvesting involves simply lifting the bags or rack to the surface and removing the mature oysters. The latter method prevents losses to some predators, but is more expensive. The Pacific oyster has been grown in the outflow of mariculture ponds. When fish or
prawn Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten. The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature' ...
s are grown in ponds, it takes typically of feed to produce of product ( dry-dry basis). The other goes into the pond and after mineralization, provides food for phytoplankton, which in turn feeds the oyster. To prevent spawning, sterile oysters are now cultured by crossbreeding
tetraploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains ...
and diploid oysters. The resulting
triploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains ...
oyster cannot propagate, which prevents introduced oysters from spreading into unwanted habitats.


Restoration and recovery

In many areas, non-native oysters have been introduced in attempts to prop up failing harvests of native varieties. For example, the
eastern oyster The eastern oyster (''Crassostrea virginica'')—also called the Atlantic oyster, American oyster, or East Coast oyster—is a species of true oyster native to eastern North and South America. Other names in local or culinary use include the We ...
(''Crassostrea virginica'') was introduced to California waters in 1875, while the Pacific oyster was introduced there in 1929. Proposals for further such introductions remain controversial. The Pacific oyster prospered in
Pendrell Sound Pendrell Sound is a sound located in the Discovery Islands in British Columbia, Canada. The sound branches off from Waddington Channel and deeply incises East Redonda Island. The northern limit of Pendrell Sound delineates part of the northern lim ...
, where the surface water is typically warm enough for spawning in the summer. Over the following years, spat spread out sporadically and populated adjacent areas. Eventually, possibly following adaptation to the local conditions, the Pacific oyster spread up and down the coast and now is the basis of the North American west coast oyster industry. Pendrell Sound is now a reserve that supplies spat for cultivation. Near the mouth of the
Great Wicomico River The Great Wicomico River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map , accessed April 1, 2011 river in the U.S. state of Virginia, located approximately northeast of Richmond. In 1864, du ...
in the
Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / ...
, five-year-old
artificial reef An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing. Many ...
s now harbor more than 180 million native '' Crassostrea virginica''. That is far lower than in the late 1880s, when the bay's population was in the billions, and watermen harvested about annually. The 2009 harvest was less than . Researchers claim the keys to the project were: * using waste oyster shells to elevate the reef floor to keep the spat free of bottom sediments * building larger reefs, ranging up to in size * disease-resistant broodstock The "oyster-tecture" movement promotes the use of oyster reefs for water purification and wave attenuation. An oyster-tecture project has been implemented at Withers Estuary, Withers Swash, South Carolina, by Neil Chambers-led volunteers, at a site where pollution was affecting beach tourism. Currently, for the installation cost of $3000, roughly 4.8 million liters of water are being filtered daily. In New Jersey, however, the Department of Environmental Protection refused to allow oysters as a filtering system in Sandy Hook Bay and the Raritan Bay, citing worries that commercial shellfish growers would be at risk and that members of the public might disregard warnings and consume tainted oysters. New Jersey Baykeepers responded by changing their strategy for utilizing oysters to clean up the waterway, by collaborating with Naval Weapons Station Earle. The Navy station is under 24/7 security and therefore eliminates any poaching and associated human health risk. Oyster-tecture projects have been proposed to protect coastal cities, such as New York, from the threat of rising sea levels due to climate change. Additionally
Oyster reef restoration Oyster reef restoration refers to the process of rebuilding or restoring of oyster reefs all over the globe. Over time, oysters have been negatively affected by environmental change, such as harmful fishing techniques, over harvesting, water poll ...
has shown to increase the population of oyster beds within the oceans while also conservating the biolife within the oyster reefs.


Human impact

The accidental or intentional introduction of species by humans has the potential to negatively impact native oyster populations. For example, non-native species in
Tomales Bay Tomales Bay is a long, narrow inlet of the Pacific Ocean in Marin County in northern California in the United States. It is approximately long and averages nearly wide, effectively separating the Point Reyes Peninsula from the mainland of Mar ...
have resulted in the loss of half of California's
Olympia oyster ''Ostrea lurida'', common name the Olympia oyster, after Olympia, Washington in the Puget Sound area, is a species of edible oyster, a marine bivalve mollusk in the family Ostreidae. This species occurs on the northern Pacific coast of North A ...
s. In October 2017, it was reported that underwater noise pollution can affect oysters as they close their shells when exposed to low frequencies of sounds in
experimental An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a ...
conditions. Oysters rely on hearing waves and currents to regulate their circadian rhythms, and perception of weather events—such as
rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...
—may induce
spawning Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquat ...
. Cargo ships, pile drivers, and explosions conducted underwater produce low frequencies that may be detected by oysters. Environmental stressors as a result of
global change Global change in broad sense refers to planetary-scale changes in the Earth system. It is most commonly use to encompass the variety of changes connected to the rapid increase in human activities which started around mid-20th century, i.e. the ...
are also negatively impacting oysters around the world, with many impacts affecting molecular, physiological, and behavioral processes in species including ''Magallana gigas.''


As food

Jonathan Swift Jonathan Swift (30 November 1667 – 19 October 1745) was an Anglo-Irish satirist, author, essayist, political pamphleteer (first for the Whigs, then for the Tories), poet, and Anglican cleric who became Dean of St Patrick's Cathedral, Dubl ...
is quoted as having said, "He was a bold man that first ate an oyster". Evidence of oyster consumption goes back into prehistory, evidenced by oyster middens found worldwide. Oysters were an important food source in all coastal areas where they could be found, and oyster fisheries were an important industry where they were plentiful. Overfishing and pressure from diseases and pollution have sharply reduced supplies, but they remain a popular treat celebrated in
oyster festival An oyster festival is a food festival centered on the oyster. There are a number of oyster festivals worldwide, including the following: Australia * The Brisbane Water Oyster Festival — Woy Woy, New South Wales * Narooma, New South Wales &md ...
s in many cities and towns. It was once assumed that oysters were only safe to eat in months with the letter 'r' in their English and French names. This myth is based in truth, in that in the Northern Hemisphere, oysters are much more likely to spoil in the warmer months of May, June, July, and August. In recent years, pathogens such as ''
Vibrio parahaemolyticus ''Vibrio parahaemolyticus'' (V. parahaemolyticus) is a curved, rod-shaped, Gram-negative bacterium found in the sea and in estuaries which, when ingested, may cause gastrointestinal illness in humans. ''V. parahaemolyticus'' is oxidase positiv ...
'' have caused outbreaks in several harvesting areas of the eastern United States during the summer months, lending further credence to this belief.


Dishes

Oysters can be eaten on the half shell, raw, smoked,
boiled Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. T ...
, baked, fried,
roasted Roasting is a cooking method that uses dry heat where hot air covers the food, cooking it evenly on all sides with temperatures of at least from an open flame, oven, or other heat source. Roasting can enhance the flavor through caramelizatio ...
, stewed, canned,
pickled Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is called ...
,
steamed Steaming is a method of cooking using steam. This is often done with a food steamer, a kitchen appliance made specifically to cook food with steam, but food can also be steamed in a wok. In the American southwest, steam pits used for cooking hav ...
, or
broiled Grilling is a form of cooking that involves dry heat applied to the surface of food, commonly from above, below or from the side. Grilling usually involves a significant amount of direct, radiant heat, and tends to be used for cooking meat a ...
, or used in a variety of drinks. Eating can be as simple as opening the shell and eating the contents, including juice.
Butter Butter is a dairy product made from the fat and protein components of churned cream. It is a semi-solid emulsion at room temperature, consisting of approximately 80% butterfat. It is used at room temperature as a spread, melted as a condimen ...
and
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
are often added. Poached oysters can be served on toast with a cream
roux Roux () is a mixture of flour and fat cooked together and used to thicken sauces. Roux is typically made from equal parts of flour and fat by weight. The flour is added to the melted fat or oil on the stove top, blended until smooth, and cook ...
. In the case of
Oysters Rockefeller Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not ...
, preparation can be very elaborate. They are sometimes served on edible seaweed, such as
brown algae Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and p ...
. Care should be taken when consuming oysters. They may be eaten raw, with no dressing or with
lemon The lemon (''Citrus limon'') is a species of small evergreen trees in the flowering plant family Rutaceae, native to Asia, primarily Northeast India (Assam), Northern Myanmar or China. The tree's ellipsoidal yellow fruit is used for culin ...
juice,
vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to eth ...
(most commonly
shallot The shallot is a botanical variety (a cultivar) of the onion. Until 2010, the (French red) shallot was classified as a separate species, ''Allium ascalonicum''. The taxon was synonymized with '' Allium cepa'' (the common onion) in 2010, as the ...
vinegar), or
cocktail sauce Cocktail sauce, also known as seafood sauce, is one of several types of cold or room temperature sauces often served as part of a dish referred to as a seafood cocktail or as a condiment with other seafoods. The sauce, and the dish for which it i ...
. Upscale restaurants pair raw oysters with
mignonette sauce Mignonette sauce is a condiment made with minced shallots, cracked pepper, and vinegar traditionally served with raw oysters. The French term term ''mignonnette'' originally referred to a sachet of peppercorns, cloves, and spices used to flavo ...
, which consists primarily of fresh chopped
shallot The shallot is a botanical variety (a cultivar) of the onion. Until 2010, the (French red) shallot was classified as a separate species, ''Allium ascalonicum''. The taxon was synonymized with '' Allium cepa'' (the common onion) in 2010, as the ...
, mixed
pepper Pepper or peppers may refer to: Food and spice * Piperaceae or the pepper family, a large family of flowering plant ** Black pepper * ''Capsicum'' or pepper, a genus of flowering plants in the nightshade family Solanaceae ** Bell pepper ** Chili ...
corn, dry
white wine White wine is a wine that is fermented without skin contact. The colour can be straw-yellow, yellow-green, or yellow-gold. It is produced by the alcoholic fermentation of the non-coloured pulp of grapes, which may have a skin of any colour. ...
and lemon juice or sherry vinegar. Like fine wine, raw oysters have complex flavors that vary greatly among varieties and regions: salty, briny, buttery, metallic or fruity. The texture is soft and fleshy, but crisp on the palate. North American varieties include
Kumamoto is the capital city of Kumamoto Prefecture on the island of Kyushu, Japan. , the city has an estimated population of 738,907 and a population density of 1,893 people per km2. The total area is 390.32 km2. had a population of 1,461,000, ...
and
Yaquina Bay Yaquina Bay ( ) is a coastal estuarine community found in Newport, Oregon, United States. Yaquina Bay is a semi-enclosed body of water, approximately 8 km² (3.2 mi²) in area, with free connection to the Pacific Ocean, but also diluted ...
from Oregon,
Duxbury Duxbury (alternative older spelling: "Duxborough") is a historic seaside town in Plymouth County, Massachusetts, United States. A suburb located on the South Shore approximately to the southeast of Boston, the population was 16,090 at the 20 ...
and Wellfleet from Massachusetts, Malpeque from
Prince Edward Island Prince Edward Island (PEI; ) is one of the thirteen provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has several nicknames: "Garden of the Gulf", ...
, Canada, Blue Point from Long Island, New York, Pemaquid from
Maine Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and ...
,
Rappahannock River The Rappahannock River is a river in eastern Virginia, in the United States, approximately in length.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed April 1, 2011 It traverses the entir ...
from Virginia, Chesapeake from Maryland and
Cape May Cape May consists of a peninsula and barrier island system in the U.S. state of New Jersey. It is roughly coterminous with Cape May County and runs southwards from the New Jersey mainland, separating Delaware Bay from the Atlantic Ocean. The so ...
from New Jersey. Variations in water salinity, alkalinity, and mineral and nutritional content influence their flavor. File:Chargrilled oysters.jpg, Chargrilled oysters. File:FriedOyster.JPG, Fried oyster with egg and flour is a common dish in
Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
and
Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...
. File:Deep fried oysters by Kossy@FINEDAYS in Akabane.jpg, in Japan. File:Six steamed oysters on the half shell.jpg, Six steamed Eastern oysters on the half shell File:"Fine de Claire" raw oysters.jpg, Raw "Fine de Claire" oysters served at Mercado de San Miguel in
Madrid Madrid ( , ) is the capital and most populous city of Spain. The city has almost 3.4 million inhabitants and a Madrid metropolitan area, metropolitan area population of approximately 6.7 million. It is the Largest cities of the Europ ...
.


Nutrition

Oysters are an excellent source of
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
,
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
,
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
, and
selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
, as well as
vitamin A Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably ...
and vitamin B12. Oysters are low in
food energy Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscular activity. Most animals derive most of their energy from aerobic respiration, namely combining the carbohy ...
; one dozen raw oysters provides only . They are rich in protein (approximately 9 g in 100 g of Pacific oysters). Two oysters () provide the
Reference Daily Intake The Reference Daily Intake (RDI) used in nutrition labeling on food and dietary supplement products in the U.S. and Canada is the daily intake level of a nutrient that is considered to be sufficient to meet the requirements of 97–98% of healt ...
of zinc and vitamin B12. Traditionally, oysters are considered to be an
aphrodisiac An aphrodisiac is a substance that increases sexual desire, sexual attraction, sexual pleasure, or sexual behavior. Substances range from a variety of plants, spices, foods, and synthetic chemicals. Natural aphrodisiacs like cannabis or cocai ...
, partially because they resemble female sex organs. A team of American and Italian researchers analyzed bivalves and found they were rich in amino acids that trigger increased levels of
sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormones that interact with vertebrate steroid hormone receptors. The sex hormones include the androgens, estrogens, and progestogens. Their effect ...
s. Their high
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
content aids the production of testosterone.


Shucking oysters

Opening oysters, referred to as "oyster-shucking", requires skill. The preferred method is to use a special knife (called an oyster knife, a variant of a shucking knife), with a short and thick blade about long. While different methods are used to open an oyster (which sometimes depend on the type), the following is one commonly accepted oyster-shucking method. *Insert the blade, with moderate force and vibration if necessary, at the hinge between the two valves. *Twist the blade until there is a slight pop. *Slide the blade upward to cut the adductor muscle which holds the shell closed. Inexperienced shuckers can apply too much force, which can result in injury if the blade slips. Heavy gloves, sometimes sold as oyster gloves, are recommended; apart from the knife, the shell itself can be razor-sharp. Professional shuckers require fewer than three seconds to open the shell. If the oyster has a particularly soft shell, the knife can be inserted instead in the "sidedoor", about halfway along one side where the oyster lips widen with a slight indentation. Opening or "shucking" oysters has become a competitive sport. Oyster-shucking competitions are staged around the world. The Guinness World Oyster Opening Championship was held annually in September at the
Galway International Oyster Festival The Galway International Oyster Festival is a food festival held annually in Galway on the west coast of Ireland on the last weekend of September, the first month of the oyster season. Inaugurated in 1954, it was the brainchild of the Great Sout ...
, in
Galway Galway ( ; ga, Gaillimh, ) is a city in the West of Ireland, in the province of Connacht, which is the county town of County Galway. It lies on the River Corrib between Lough Corrib and Galway Bay, and is the sixth most populous city on ...
, Ireland until 2010. Since 2011, "Guinness" has been dropped from the title.Comparison of archived title of the game: * * *


Food safety and storage

Unlike most shellfish, oysters can have a fairly long shelf life of up to four weeks. However, their taste becomes less pleasant as they age. Fresh oysters must be alive just before consumption or cooking. Oysters that do not open are generally assumed to be dead before cooking and therefore unsafe. There is only one criterion: the oyster must be capable of tightly closing its shell. Open oysters should be tapped on the shell; a live oyster will close up and is safe to eat. Oysters which are open and unresponsive are dead and must be discarded. Some dead oysters, or oyster shells which are full of sand, may be closed. These make a distinctive noise when tapped, and are known as "clackers". Oysters can contain harmful
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
. Oysters are filter feeders, so will naturally concentrate anything present in the surrounding water. Oysters from the
Gulf Coast The Gulf Coast of the United States, also known as the Gulf South, is the coast, coastline along the Southern United States where they meet the Gulf of Mexico. The list of U.S. states and territories by coastline, coastal states that have a shor ...
of the United States, for example, contain high bacterial loads of human pathogens in the warm months, most notably ''
Vibrio vulnificus ''Vibrio vulnificus'' is a species of Gram-negative, motile, curved rod-shaped (bacillus), pathogenic bacteria of the genus ''Vibrio''. Present in marine environments such as estuaries, brackish ponds, or coastal areas, ''V. vulnificus'' is relat ...
'' and ''
Vibrio parahaemolyticus ''Vibrio parahaemolyticus'' (V. parahaemolyticus) is a curved, rod-shaped, Gram-negative bacterium found in the sea and in estuaries which, when ingested, may cause gastrointestinal illness in humans. ''V. parahaemolyticus'' is oxidase positiv ...
''. In these cases, the main danger is for
immunocompromised Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...
individuals, who are unable to fight off infection and can succumb to
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
, leading to death. ''Vibrio vulnificus'' is the most deadly seafood-borne
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
.


Depuration

Depuration Depuration of seafood is the process by which marine or freshwater animals are placed into a clean water environment for a period of time to allow purging of biological contaminants (such as ''Escherichia coli'') and physical impurities (such as s ...
of oysters is a common industry practice and widely researched in the scientific community but is not commonly known by end consumers. The main objective of seafood depuration is to remove fecal contamination in seafood before being sold to end consumers. Oyster depuration is useful since they are generally eaten raw and in many countries, the requirement to process is government-regulated or mandatory. The
United Nations Food and Agriculture Organization The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...
(FAO) formally recognizes depuration and has published detailed documents on the process, whereas the Codex Alimentarius, encourages the application of seafood depuration. Oyster depuration begins after the harvest of oysters from farmed locations. The oysters are transported and placed into tanks pumped with clean water for periods of 48 to 72 hours. The holding temperatures and salinity vary according to species. The seawater that the oysters were originally farmed in does not remain in the oyster, since the water used for depuration must be fully sterilized, plus the depuration facility would not necessarily be located near the farming location. Depuration of oysters can remove moderate levels of contamination of most bacterial indicators and pathogens. Well-known contaminants include ''
Vibrio parahaemolyticus ''Vibrio parahaemolyticus'' (V. parahaemolyticus) is a curved, rod-shaped, Gram-negative bacterium found in the sea and in estuaries which, when ingested, may cause gastrointestinal illness in humans. ''V. parahaemolyticus'' is oxidase positiv ...
'', a temperature-sensitive bacterium found in seawater animals, and ''Escherichia coli'', a bacterium found in coastal waters near highly populated cities having sewage systems discharging waste nearby, or in the presence of agricultural discharges. Depuration expands beyond oysters into many shellfish and other related products, especially in seafood that is known to come from potentially polluted areas; depurated seafood is effectively a product cleansed from inside-out to make it safe for human consumption.


Cultural aspects


Religious

As shellfish, consumption of oyster is forbidden by
Jewish dietary law (also or , ) is a set of dietary laws dealing with the foods that Jewish people are permitted to eat and how those foods must be prepared according to Jewish law. Food that may be consumed is deemed kosher ( in English, yi, כּשר), fro ...
. Similarly, in Islam, Jaʽafari
Shia Shīʿa Islam or Shīʿīsm is the second-largest branch of Islam. It holds that the Islamic prophet Muhammad designated ʿAlī ibn Abī Ṭālib as his successor (''khalīfa'') and the Imam (spiritual and political leader) after him, mo ...
and
Hanafi The Hanafi school ( ar, حَنَفِية, translit=Ḥanafiyah; also called Hanafite in English), Hanafism, or the Hanafi fiqh, is the oldest and one of the four traditional major Sunni schools ( maddhab) of Islamic Law (Fiqh). It is named a ...
Sunni dietary jurisprudence prohibit consuming bivalves, including oysters, as it is ''makruh'' (highly prohibited).


Diseases

Oysters are subject to various diseases which can reduce harvests and severely deplete local populations. Disease control focuses on containing infections and breeding resistant strains, and is the subject of much ongoing research. *"Dermo" is caused by a protozoan
parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
('' Perkinsus marinus''). It is a prevalent
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
, causes massive mortality, and poses a significant economic threat to the oyster industry. The disease is not a direct threat to humans consuming infected oysters. Dermo first appeared in the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
in the 1950s, and until 1978 was believed to be caused by a
fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...
. While it is most serious in warmer waters, it has gradually spread up the east coast of the United States. * Multinucleated sphere X (MSX) is caused by the protozoan '' Haplosporidium nelsoni'', generally seen as a multinucleated ''
Plasmodium ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a ver ...
''. It is infectious and causes heavy mortality in the
eastern oyster The eastern oyster (''Crassostrea virginica'')—also called the Atlantic oyster, American oyster, or East Coast oyster—is a species of true oyster native to eastern North and South America. Other names in local or culinary use include the We ...
; survivors, however, develop resistance and can help propagate resistant populations. MSX is associated with high salinity and water temperatures. MSX was first noted in
Delaware Bay Delaware Bay is the estuary outlet of the Delaware River on the northeast seaboard of the United States. It is approximately in area, the bay's freshwater mixes for many miles with the saltwater of the Atlantic Ocean. The bay is bordered inland ...
in 1957, and is now found all up and down the East Coast of the United States. Evidence suggests it was brought to the US when ''
Crassostrea gigas The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand. Etymology The genus ''Ma ...
'', Pacific oyster variety, was introduced to Delaware Bay. *Denman Island disease causes visible yellow/green pustules on the body and adductor muscles of oysters. This disease mainly affects Pacific oysters (''
Crassostrea gigas The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand. Etymology The genus ''Ma ...
''). The disease was first described in 1960 near
Denman Island Denman Island, or Sla-dai-aich (Taystayic), its Indigenous name, is one of the Northern Gulf Islands and part of the Comox Valley Regional District of British Columbia, Canada. It is a member of the Islands Trust group of islands and is home ...
off the eastern aspect of Vancouver Island, British Columbia. It was found that the causative agent of these lesions are associated with amitochondriate protistan microcells, which were later identified as '' Mikrocytos mackini.'' Some oysters also harbor bacterial species which can cause human disease; of importance is ''
Vibrio vulnificus ''Vibrio vulnificus'' is a species of Gram-negative, motile, curved rod-shaped (bacillus), pathogenic bacteria of the genus ''Vibrio''. Present in marine environments such as estuaries, brackish ponds, or coastal areas, ''V. vulnificus'' is relat ...
'', which causes gastroenteritis, which is usually self-limiting, and
cellulitis Cellulitis is usually a bacterial infection involving the inner layers of the skin. It specifically affects the dermis and subcutaneous fat. Signs and symptoms include an area of redness which increases in size over a few days. The borders of ...
. Cellulitis can be severe and rapidly spreading, requiring antibiotics, medical care, and in some severe cases amputation. It is usually acquired when the contents of the oyster come in contact with a cut skin lesion, as when shucking an oyster.


See also


References


External links


MolluSCAN eye
, a website devoted to the online study of molluscan bivalve behavior around the world, including oysters. Daily update.
World of Boats (EISCA) Collection ~ Fal Oyster Boat, Sunny South


* {{Authority control Ostreida Dishes involving the consumption of live animals Symbols of Mississippi Smoked food Mollusc common names Aphrodisiac foods