The Pacific oyster, Japanese oyster, or Miyagi oyster (''Magallana gigas''), is an

oyster 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 ...

native to the Pacific coast of

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

. It has become an

introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

Etymology

The genus ''Magallana'' is named for the Portuguese explorer

Ferdinand Magellan Ferdinand Magellan ( or ; pt, Fernão de Magalhães, ; es, link=no, Fernando de Magallanes, ; 4 February 1480 – 27 April 1521) was a Portuguese explorer. He is best known for having planned and led the 1519 Spanish expedition to the Eas ...

and its specific epithet ''gígās'' is from the Greek for "giant". It was previously placed in the genus '' Crassostrea''; from the

Latin Latin (, or , ) is a classical language belonging to the Italic languages, 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 ...

''crass'' meaning "thick", ''ostrea'' meaning "oyster", and ''Crassostrea gigas'' is considered by part of the scientific community to be the proper denomination as an accepted alternative in

WoRMS Worms may refer to: *Worm, an invertebrate animal with a tube-like body and no limbs Places *Worms, Germany Worms () is a city in Rhineland-Palatinate, Germany, situated on the Upper Rhine about south-southwest of Frankfurt am Main. It had ...

Description

The shell of ''M. gigas'' varies widely with the environment where it is attached. Its large, rounded, radial folds are often extremely rough and sharp. The two valves of the shell are slightly different in size and shape, the right valve being moderately

concave Concave or concavity may refer to: Science and technology * Concave lens * Concave mirror Mathematics * Concave function, the negative of a convex function * Concave polygon, a polygon which is not convex * Concave set In geometry, a subset o ...

. Shell colour is variable, usually pale white or off-white. Mature specimens can vary from 80 to 400 mm long.

Right and left valve of the same specimen: File:Magallana gigas 01.jpg, Right valve File:Magallana gigas 02.jpg, Left valve

Ecology

Habitat

''M. gigas'' is an estuarine

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

, but can also be found in

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...

and subtidal zones. They prefer to attach to hard or rocky surfaces in shallow or sheltered waters up to 40 m deep, but have been known to attach to muddy or sandy areas when the preferred habitat is scarce. The Pacific oyster can also be found on the shells of other animals.

Larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. T ...

often settle on the shell of adults, and great masses of

s can grow together to form

reefs. The optimum salinity for Pacific oysters is between 20 and 35 parts per thousand (ppt), and they can tolerate salinities as high as 38 ppt; at this level, however, reproduction is unlikely to occur.Pacific Oyster factsheet
Food and Agriculture Organization of the United Nations (FAO) The Pacific oyster is also a very temperature tolerant

, as it can withstand a range from −1.8 to 35 °C.

Biology

Sexuality

The Pacific oyster has separate sexes, but

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have ...

s sometimes do exist.Quayle, D.B (1969). ''Pacific oyster culture in British Columbia'', p. 23. First Edition. Ottawa: The Queen’s Printer. Their sex can be determined by examining the

gonad 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 sp ...

s, and it can change from year to year, normally during the winter. In certain environmental conditions, one sex is favoured over the other. Protandry is favoured in areas of high food abundance and protogyny occurs in areas of low food abundance. In habitats with a high food supply, the

sex ratio The sex ratio (or gender ratio) is usually defined as the ratio of males to females in a population. As explained by Fisher's principle, for evolutionary reasons this is typically about 1:1 in species which reproduce sexually. Many species dev ...

in the adult population tends to favour females, and areas with low food abundances tend to have a larger proportion of male adults.

Spawning

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 ...

in the Pacific oyster occurs at 20 °C. This species is very fecund, with females releasing about 50–200 million eggs in regular intervals (with a rate at 5–10 times a minute) in a single

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 ...

. Once released from the

s, the eggs move through the suprabranchial chambers (

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 ar ...

s), are then pushed through the

ostia into the mantle chamber, and finally are released in the water, forming a small cloud. In males, the sperm is released at the opposite end of the oyster, along with the normal exhalent stream of water. A rise in water temperature is thought to be the main cue in the initiation of spawning, as the onset of higher water temperatures in the summer results in earlier spawning in the Pacific oyster.

Life cycle

The

larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. T ...

of the Pacific oyster are planktotrophic, and are about 70 µm at the prodissoconch 1 stage. The larvae move through the water column via the use of a larval foot to find suitable settlement locations. They can spend several weeks at this phase, which is dependent on water temperature, salinity, and food supply. Over these weeks, larvae can disperse great distances by water currents before they metamorphose and settle as small spat. Similar to other oyster

, once a Pacific oyster larva finds a suitable

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 ...

, it attaches to it permanently using cement secreted from a gland in its foot. After settlement, the larva metamorphoses into a juvenile spat. The growth rate is very rapid in optimum environmental conditions, and market size can be achieved in 18 to 30 months. Unharvested Pacific oysters can live up to 30 years.

Genetics

The genome of ''M. gigas'' has been sequenced, revealing an extensive set of genes that enables it to cope with environmental stresses. The expression of genes such as arginine kinase and cavortin is particularly important in regulating the metabolic response of this species to stress events including the reduction of seawater pH, as observed under ocean acidification.

Aquaculture

Historical background

''M. gigas'' was originally described by the Swedish naturalist

Carl Peter Thunberg Carl Peter Thunberg, also known as Karl Peter von Thunberg, Carl Pehr Thunberg, or Carl Per Thunberg (11 November 1743 – 8 August 1828), was a Swedish naturalist and an "apostle" of Carl Linnaeus. After studying under Linnaeus at Uppsala U ...

in 1795. It is native to the Northwest Pacific, and occurs primarily in temperate waters between 30° N and 48° N. It is now the most widely farmed and commercially important

in the world, as it is very easy to grow, environmentally tolerant, and easily spread from one area to another. The most significant introductions were to the Pacific Coast of 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 Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

in the 1920s and to

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

in 1966. In most places, the Pacific oyster was introduced to replace the native oyster stocks which were seriously dwindling due to overfishing or disease. In addition, this species was introduced to create an industry that was previously not available at all in that area. In addition to intentional introductions, the Pacific oyster has spread through accidental introductions either through larvae in

ballast Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship ...

water or on the hulls of ships. In some places in the world, though, it is considered by biosecurity, primary industry, and conservation departments and ministries to be an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...

, where it is outcompeting native species, such as the Olympia oyster in

Puget Sound Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected m ...

, Washington; the rock oyster, '' Saccostrea commercialis'', in the North Island of

; and the blue mussel, '' Mytilus edulis'', in the

Wadden Sea The Wadden Sea ( nl, Waddenzee ; german: Wattenmeer; nds, Wattensee or ; da, Vadehavet; fy, Waadsee, longname=yes; frr, di Heef) is an intertidal zone in the southeastern part of the North Sea. It lies between the coast of northwestern conti ...

Production techniques

Numerous methods are used in the production of Pacific oysters. These techniques depend on factors such as the seed supply resources, the environmental conditions in the region, and the market product, i.e., whether the

s are sold in a half shell, or shelled for meat extraction. Production can either be entirely sea-based or rely on hatcheries for seed supply.

Seed supply

Most of the global Pacific oyster spat supply comes from the wild, but some is now produced by hatchery methods. The seed from the wild can either be collected by the removal of seaweed from beaches or by hanging shell ( cultch) in suspension from long lines in the open water. The movement towards hatchery-reared spat is important, as wild seed is susceptible to changeable environmental conditions, such as toxic algal blooms, which can halt the supply of seed from that region. In addition, several pests have been noted as considerable dangers to oyster seed. The Japanese oyster drill ('' Ocenebra inornata''), flatworm ('' Koinostylochus ostreophagus''), and parasitic copepod ('' Mytilicola orientalis'') have been introduced accidentally to

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

areas, and have had serious impacts on oyster production, particularly in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...

and

Broodstock

Pacific oyster broodstocks in hatcheries are kept in optimum conditions so the production of large amounts of high quality eggs and

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...

can be achieved. Pacific oyster females are very fecund, and individuals of 70–100 g live weight can produce 50–80 million eggs in a single

spawn Spawn or spawning may refer to: * Spawn (biology), the eggs and sperm of aquatic animals Arts, entertainment, and media * Spawn (character), a fictional character in the comic series of the same name and in the associated franchise ** '' Spawn: A ...

. Broodstock adults are held in tanks at 20–22 °C, supplied with cultured

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...

and with

salinities Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

of 25–32 ppt. These individuals can be induced to spawn by thermal shock treatment. Yet, the eggs from a small

sample Sample or samples may refer to: Base meaning * Sample (statistics), a subset of a population – complete data set * Sample (signal), a digital discrete sample of a continuous analog signal * Sample (material), a specimen or small quantity of ...

of females (about six) are more commonly stripped from the

s using

Pasteur pipette An eye dropper, also called Pasteur pipette or simply dropper, is a device used to transfer small quantities of liquids. They are used in the laboratory and also to dispense small amounts of liquid medicines. A very common use was to dispense e ...

s and fertilized by

from a similar number of males.

Larval and postlarval culture

Pacific oysters have a

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

veliger

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

l stage which lasts from 14–18 days. In the hatcheries, they are kept at temperatures of 25–28 °C with an optimum salinity between 20 and 25%. Early-stage veligers (<120 nm shell length) are fed daily with

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and thei ...

d algal species (''

Isochrysis galbana ''Isochrysis galbana'' is a species of Haptophyta. It is the type species of the genus ''Isochrysis''. It is an outstanding food for various bivalve larvae and is now widely cultured for use in the bivalve aquaculture industry. This unicellular ...

'' or '' Pavlova lutherii'') along with

diatom A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...

species (either ''

Chaetoceros calcitrans ''Chaetoceros'' is probably the largest genus of marine planktonic diatoms with approximately 400 species described, although many of these descriptions are no longer valid. It is often very difficult to distinguish between different ''Chaeto ...

'' or '' Thalassiosira pseudonana''). The larvae are close to a settlement stage when dark eye spots and a foot develop. During this time, settlement materials (cultch), such as roughed PVC sheets, fluted PVC pipes, or shells, are placed into the tanks to encourage the larvae to attach and settle. However, particularly on the US West Coast, mature larvae are commonly packed and shipped to oyster farms, where the farmers set the oysters themselves.

Nursery

Pacific oyster spat can be grown in nurseries by sea-based or land-based upwelling systems. Nursery culture reduces mortality in small spat, thus increasing the farm's efficiency. Sea-based nursery systems are often located in

estuarine An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...

areas where the spat are mounted on barges or rafts. Land-based nursery systems have spat mounted on barges in large saltwater tanks, which either have a natural algae supply or are enriched with nutrients from fertilizers.

Ongrowing techniques

This stage of oyster culture is almost completely sea-based. A range of bottom, off-bottom, suspended, and floating cultures are used. The technique used depends on site-specific conditions, such as tidal range, shelter, water depth, current flow, and nature of substrate. Pacific oysters take 18–30 months to develop to the market size of 70–100 g live weight ( shell on). Growth from spat to adults in this species is very rapid at temperatures of 15–25 °C and at salinities of 25 to 32 ppt.

General production

In 2000, the Pacific oysters accounted for 98% of the world's cultured oyster production, and are produced in countries all over the world.

Production statistics

Global production has increased from about 150 thousand

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

s in 1950 to 1.2 million tonnes in 1990. By 2003, global production had increased to 4.38 million tonnes. The majority was in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

, which produced 84% of the global production.

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

and the

Republic of Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korean Peninsula and sharing a land border with North Korea. Its western border is formed by the Yellow Sea, while its ea ...

also contributed, producing 261 000, 238 000 and 115 000 tonnes, respectively. The other two major producers are the

(43 000 tonnes) and

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the no ...

(23 000 tonnes). In 2003, global Pacific oyster production was worth $ 3.69 billion.

Current issues

Virus management

Pacific oysters are nonspecific

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

s, which means they ingest any particulate matter in the water column. This presents major issues for

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

management of open-water

shellfish Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environ ...

farms, as shellfish like the Pacific oyster have been found to contain

norovirus Norovirus, sometimes referred to as the winter vomiting disease, is the most common cause of gastroenteritis. Infection is characterized by non-bloody diarrhea, vomiting, and stomach pain. Fever or headaches may also occur. Symptoms usually devel ...

strains which can be harmful to humans. Globally, noroviruses are the most common cause of nonbacterial

gastroenteritis Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydr ...

, and are introduced into the water column by faecal matter, either from

sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from reside ...

discharge or land runoff from nearby farmland.

Heavy metal pollution

Pacific oysters, like other shellfish, are able to remove

heavy metals upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as ...

, such as

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 ...

and

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...

, as well as biotoxins (microscopic toxic

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. ...

), from the surrounding water. These can accumulate in the tissues of the animal and leave it unharmed (

bioaccumulation Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...

). However, when the concentrations of the metals or biotoxins are high enough, shellfish poisoning can result when they are consumed by humans. Most countries have strict water regulations and legislation to minimise the occurrence of such poisoning cases. Scottish water quality regulations
Irish water quality regulations
American water quality regulations

Diseases

Various diseases are known to affect Pacific oyster:

Predators

Numerous

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...

s are known to damage Pacific oyster stocks.
Nonindigenous aquatic species of concern for Alaska: Pacific oyster fact sheet Several crab species (''

Metacarcinus magister The Dungeness crab (''Metacarcinus magister'') is a species of crab inhabiting eelgrass beds and water bottoms along the west coast of North America. It typically grows to across the carapace and is a popular seafood. Its common name comes from ...

'', ''

Cancer productus ''Cancer productus'', one of several species known as red rock crabs, is a crab of the genus '' Cancer'' found on the western coast of North America. This species is commonly nicknamed the Pearl of the Pacific Northwest. Description ''Cancer ...

'', ''

Metacarcinus gracilis The graceful rock crab or slender crab, ''Metacarcinus gracilis'' (the naming convention recognized by WoRMS) or ''Cancer gracilis'' (the naming convention recognized by ITIS), is one of only two members of the genus ''Metacarcinus,'' recognized ...

''), oyster drills, and starfish species ('' Pisater ochraceus'', '' Pisater brevispinus'', '' Evasterias troschelii'', and ''

Pycnopodia helianthoides ''Pycnopodia helianthoides'', commonly known as the sunflower sea star, is a large sea star found in the northeast Pacific. The only species of its genus, it is among the largest sea stars in the world, with a maximum arm span of . Adult sunflow ...

'') can cause severe impacts to oyster culture.

Competition with other uses of the seashore

Increasing numbers of frames for oysters to grow on has led to claims that the character of the beach is changed and that other users may be endangered. In the preparations for the Tokyo 2020/2021 Summer Olympics, equipment for the canoeing and

rowing Rowing is the act of propelling a human-powered watercraft using the sweeping motions of oars to displace water and generate reactional propulsion. Rowing is functionally similar to paddling, but rowing requires oars to be mechanically ...

was found to be contaminated with of ''M. gigas'', necessitating US$1,280,000/£930,000 in removal expenditures.

Ocean acidification

Ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...

due to increasing atmospheric carbon dioxide impacts shellfish such as oysters. The increasing acidity of the ocean reduces oyster reproduction, lowers the survival rate of juvenile oysters, and causes delayed

sexual maturation Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definiti ...

. Overall, these effects combine to lower recruitment to oyster populations, reduce the

maximum sustainable yield In population ecology and economics, maximum sustainable yield (MSY) is theoretically, the largest yield (or catch) that can be taken from a species' stock over an indefinite period. Fundamental to the notion of sustainable harvest, the concept of ...

that can be harvested, and reduce the profitability of oyster farms. It is unknown if acidification alters the flavor of shellfish or other qualities that make them desirable for human consumption.

Productivity

Productivity Productivity is the efficiency of production of goods or services expressed by some measure. Measurements of productivity are often expressed as a ratio of an aggregate output to a single input or an aggregate input used in a production proces ...

of the Pacific oyster can be described as the amount of meat produced in relation to the amount of seed planted on cultch. The productivity of a farm also depends on the interaction of biotic factors, such as mortality, growth, and oyster size, as well as the quality of the seed and the growing technique used (off bottom, bottom, suspended or floating culture). The main causes of mortality in the Pacific oysters are natural mortality (age), predators, disease, environmental conditions (ice, freak winds), competition for space (crowding of cultch), silting (sediment runoff from land), and cluster separation (process of breaking up clusters of oysters into as many individual oysters as possible).

Aquaculture in New Zealand

In New Zealand, the Pacific oyster was unintentionally introduced in the 1950s, most likely through ballast water and from the hulls of ships. Aquaculture.govt.nz Aquaculture farmers at the time noticed the Pacific oyster outcompeted the endemic species, the Sydney rock oyster (''Saccostrea glomerata''), which naturally occurs in intertidal areas in the North Island.
TeAra: The encyclopaedia of New Zealand Early experiments in rock oyster cultivation procedures attached spat to cement-covered sticks and laid them down in racks. The farmers noticed, however, the Pacific oyster outgrew the

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

in most areas, and constantly was attaching to the rock oyster collection sticks. A few years later, Pacific oysters were the dominant species in the farms, as it grew three times faster than the rock oyster, produced a reliable and constant supply of spat, and had an already established market overseas. In 1977, the Pacific oyster was accidentally introduced to the

Marlborough Sounds The Marlborough Sounds are an extensive network of sea-drowned valleys at the northern end of the South Island of New Zealand. The Marlborough Sounds were created by a combination of land subsidence and rising sea levels. According to Māori ...

, and farming began there in the 1990s. Marlborough farmers developed a different method of cultivation in comparison to the North Island method of racks; they instead suspended their oysters on longlines.

Production status

The Pacific oyster is one of the three main aquaculture species in New Zealand along with

king salmon The Chinook salmon (''Oncorhynchus tshawytscha'') is the largest and most valuable species of Pacific salmon in North America, as well as the largest in the genus '' Oncorhynchus''. Its common name is derived from the Chinookan peoples. Other v ...

and the greenshell mussels. Pacific oyster aquaculture production has grown from an export value of $11 million in 1986 to $32 million in 2006.
Aquaculture.govt.nz: farmed species In 2006, the 23 Pacific oyster farms throughout New Zealand covered a total of 750 hectares of marine space and produced 2,800 tonnes of product per year. Annual production is now between about 3,300 and 4,000

s. In 2005, the value of New Zealand's Pacific oyster production was $12 million domestically, and $16.9 million for export. New Zealand Government, Blue Horizon document New Zealand's main export markets are Japan, Korea, the US, the EU and Australia. However, research has demonstrated that changes in global ocean temperature and the advent of ocean acidification may alter the growth, reproduction, and development of this species with variable responses

References

External links

Clara Massapina, Sandra Joaquim, Domitilia Matias and Nicole Devauchelle, ''Oocyte and embryo quality in Crassostrea gigas (Portuguese strain) during a spawning period in Algarve, South Portugal''; Aquat. Living Resour. 12 (1999) 327–333

Crassostrea gigas
Food and Agriculture Organization of the United Nations

United States

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

* http://findarticles.com/p/articles/mi_m0QPU/is_2_24/ai_n15384489 * https://web.archive.org/web/20061223014748/http://www.stefannehring.de/downloads/142_Nehring-2003_Aliens-17_pacific-oyster.pdf {{Taxonbar, from=Q20857 Magallana Molluscs of the Pacific Ocean Marine molluscs of Asia Bivalves of Asia Commercial molluscs Bivalves described in 1793 Articles containing video clips Taxa named by Carl Peter Thunberg