Pacific oyster
Encyclopedia
The Pacific oyster, Japanese oyster or Miyagi oyster (Crassostrea 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
.
, but can also be found in intertidal and subtidal zones. They prefer to attach to hard or rocky surfaces in shallow or sheltered waters up to 40m 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
often settle on the shell of adults, and great masses of oyster
s can grow together to form oyster
reefs. The optimum salinity for Pacific oysters is between 20 and 25 ‰ (parts per thousand), and they can tolerant salinities as high as 35‰; at this level, however, reproduction is unlikely to occur. The pacific oyster is also very a temperature tolerant species
, as it can withstand a range from -1.8 to 35°C.
s sometimes do exist. Their sex can be determined by examining the gonad
s, and it can change from year to year, normally during the winter months. 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
in the adult population tends to favour females, and areas with low food abundances tend to have a larger proportion of male adults.
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
. Once released from the gonad
s, the eggs move through the suprabranchial chambers (gill
s), are then pushed through the gill
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.
The larvae
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 species
, once the Pacific oyster larvae
find a suitable habitat
, they attach to it permanently using cement secreted from a gland in their foot. After settlement, the larvae metamorphose into 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.
naturalist, Carl Peter Thunberg
in 1795. It originated from Japan
, where it has been cultured for hundreds of years. It is now the most widely farmed and commercially important oyster
in the world, as it is very easy to grow, environmentally tolerant and is easily spread from one area to another. The most significant introductions were to the Pacific coast of America
in the 1920s and to France
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. As well as intentional introductions, the Pacific oyster has spread through accidental introductions either through larvae
in ballast
water or on the hulls of ships. In some places in the world, though, it is considered by some to be an invasive species
, where it is outcompeting native species, such as the Olympia oyster
in Puget Sound
, Washington, the rock oyster, Saccostrea commercialis in the North Island of New Zealand
and the blue mussel, Mytilus edulis, in the Wadden Sea
.
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.
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 longlines 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 japonica), flatworm (Pseudostylochus osterophagus), and parasitic copepod (Mytlilcola orientalis) have been introduced accidentally to aquaculture
areas, and have had serious impacts on oyster production, particularly in British Columbia
and Europe
.
in hatcheries are kept in optimum conditions so the production of large amounts of high quality eggs
and sperm
can be achieved. Pacific oyster females are very fecund
, and individuals of 70-100g live weight can produce 50-80 million eggs
in a single spawn
. Broodstock
adults are held in tanks at 20-22°C, supplied with cultured algae
and with salinities
of 25-32‰. These individuals can be induced to spawn by thermal shock treatment. Yet, it is more common for the eggs from a small sample
of females (about 6) to be stripped from the gonad
s using Pasteur pipette
s and fertilized by sperm
from a similar number of males.
veliger
larva
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 veliger
s (<120 nm shell length) are fed daily with flagellate
algae
species
(Isochrysis galbana or Pavlova lutherii) along with diatom
species
(either Chaetoceros calcitrans or Thalassiosira pseudonana). The larva
e 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. It is common, however, particularly in on the US West Coast, for the mature larvae to be packed and shipped to oyster farms where the farmers set the oysters themselves.
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.
culture is almost completely sea-based. A range of bottom, off-bottom, suspended and floating cultures are used. The type of technique used depends on site-specific conditions, such as tidal range, shelter, water depth, current flow and nature of substratum
. Pacific oysters take 18– 30 months to develop to the market size of 70-100g 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‰.
s in 1950 to a peak of 750 tonnes in 1980. By 2003, global production had increased to 4.38 million tonnes. The majority was in China
, which produced 84% of the global production. Japan
, France
and the Republic of Korea
also contributed, producing 261 000, 238 000 and 115 000 tonnes produce, respectively. The other two major producers are the United States
(43 000 tonnes) and Taiwan
(23 000 tonnes). In 2003, global Pacific oyster production was worth $ 3.69 billion, with Asia
contributing over half of this amount.
s, which means they ingest any particulate matter in the water column. This presents major issues for virus
management of open water shellfish
farms, as shellfish like the Pacific oyster have been found to contain norovirus strains which can be harmful to humans. Globally, noroviruses are the most common cause of nonbacterial gastroenteritis
, and are introduced into the water column by faecal
matter, either from sewage
discharge or land runoff from nearby farmland. Numerous gastroenteritis outbreaks in the world have been directly caused by the consumption of shellfish
from polluted areas.
, such as zinc
and copper
, as well as biotoxins
(microscopic toxic phytoplankton
), from the surrounding water. These can accumulate in the tissues of the animal and leave it unharmed (bioaccumulation
). However, when the concentrations of the metals or biotoxins are high enough, shellfish poisoning
can result when they are consumed by humans. High copper concentration in Pacific oyster can be recognised by the meat turning a grass-green colour. Most countries have strict water regulations and legislation to minimise the occurrence of such poisoning cases.
of the Pacific oyster
can be discussed 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 four main causes of mortality in the Pacific oyster, these are:
, the Pacific oyster was unintentionally introduced in 1950s, most likely through ballast
water and from the hulls of ships. Aquaculture farmers at the time noticed the Pacific oyster outcompeted the endemic species, rock oyster (Saccostrea commercialis), which naturally occurs in intertidal areas in the North Island. 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 species
in most areas, and constantly was attaching to the rock oyster collection sticks. A few years later, Pacific oysters were the dominant oyster
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
, 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.
in New Zealand
along with king salmon
and the greenshell mussel
s. Pacific oyster aquaculture production has grown from an export value of $11 million in 1986 to $32 million in 2006. In 2006, there were 23 Pacific oyster farms throughout New Zealand, which cover a total of 750 hectares of marine space and produce 2,800 tonnes of product per year. Annual production is now between about 3,300 and 4,000 tonne
s. In 2005, the value of New Zealand's Pacific oyster production was $12 million domestically, and $16.9 million for export. New Zealand’s main export markets are Japan, Korea, the US, the EU and Australia.
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
native to the Pacific coast of Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. It has become an introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
.
Etymology
The species name comes from the Greek crass meaning thick, ostrea meaning oyster and gígās meaning giant.Description
The shell of Crassostrea gigas varies widely with the environment where it is attached. There are large rounded radial folds that 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. Shell colour is variable, usually pale white or off-white. Mature specimens can vary from 80 mm to 400 mm long.Habitat
Crassostrea gigas is an estuarine speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, but can also be found in intertidal and subtidal zones. They prefer to attach to hard or rocky surfaces in shallow or sheltered waters up to 40m 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
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
often settle on the shell of adults, and great masses of oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
s can grow together to form oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
reefs. The optimum salinity for Pacific oysters is between 20 and 25 ‰ (parts per thousand), and they can tolerant salinities as high as 35‰; at this level, however, reproduction is unlikely to occur. The pacific oyster is also very a temperature tolerant species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, as it can withstand a range from -1.8 to 35°C.
Sexuality
The Pacific oyster has separate sexes, however hermaphroditeHermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
s sometimes do exist. Their sex can be determined by examining the gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s, and it can change from year to year, normally during the winter months. In certain environmental conditions, one sex is favoured over the other. Protandry
Dichogamy
Sequential hermaphroditism is a type of hermaphroditism that occurs in many fish, gastropods and plants. Here, the individual is born one sex and changes sex at some point in their life. They can change from a male to female , or from female to male...
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
Sex ratio
Sex ratio is the ratio of males to females in a population. The primary sex ratio is the ratio at the time of conception, secondary sex ratio is the ratio at time of birth, and tertiary sex ratio is the ratio of mature organisms....
in the adult population tends to favour females, and areas with low food abundances tend to have a larger proportion of male adults.
Spawning
SpawningSpawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
in the Pacific oyster occurs at 20°C. This species is very fecund
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
, 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 (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
. Once released from the gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s, the eggs move through the suprabranchial chambers (gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s), are then pushed through the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
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
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
of the Pacific oyster are planktotrophic
Marine larval ecology
Marine larval ecology is the study of the factors influencing the dispersing larval stage exhibited by many marine invertebrates and fishes. Marine organisms with a larval stage usually release large numbers of larvae into the water column, where these larvae develop and grow for a certain period...
, and are about 70 µm at the prodissoconch
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
1 stage. The larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
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
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
can disperse great distances by water currents before they metamorphose
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
and settle as small spat
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
. Similar to other oyster species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, once the Pacific oyster larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
find a suitable habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
, they attach to it permanently using cement secreted from a gland in their foot. After settlement, the larvae metamorphose into 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.
Historical background
The Pacific oyster (Crassostrea gigas) was named by a SwedishSweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
naturalist, Carl Peter Thunberg
Carl Peter Thunberg
Carl Peter Thunberg aka Carl Pehr Thunberg aka Carl Per Thunberg was a Swedish naturalist and an apostle of Carl Linnaeus. He has been called "the father of South African botany" and the "Japanese Linnaeus"....
in 1795. It originated from Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, where it has been cultured for hundreds of years. It is now the most widely farmed and commercially important oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
in the world, as it is very easy to grow, environmentally tolerant and is easily spread from one area to another. The most significant introductions were to the Pacific coast of America
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in the 1920s and to France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
in 1966. In most places, the Pacific oyster was introduced to replace the native oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
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. As well as intentional introductions, the Pacific oyster has spread through accidental introductions either through larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
in ballast
Sailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...
water or on the hulls of ships. In some places in the world, though, it is considered by some to be an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
, where it is outcompeting native species, such as the Olympia oyster
Olympia oyster
The Olympia oyster, Ostreola conchaphila, is the native oyster of the Pacific coast of North America from Alaska to Mexico. The name is derived from the important 19th century oyster industry near Olympia, Washington, in Puget Sound....
in Puget Sound
Puget Sound
Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...
, Washington, the rock oyster, Saccostrea commercialis in the North Island of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
and the blue mussel, Mytilus edulis, in the Wadden Sea
Wadden Sea
The Wadden Sea is an intertidal zone in the southeastern part of the North Sea. It lies between the coast of northwestern continental Europe and the range of Frisian Islands, forming a shallow body of water with tidal flats and wetlands. It is rich in biological diversity...
.
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 oysterOyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
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; some, however, is now produced by hatcheryHatchery
A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled conditions; alternatively, it may be for economic reasons A hatchery is a...
methods. The seed from the wild can either be collected by the removal of seaweed from beaches or by hanging shell (cultch
Oyster farming
Oyster farming is an aquaculture practice in which oysters are raised for human consumption. Oyster farming most likely developed in tandem with pearl farming, a similar practice in which oysters are farmed for the purpose of developing pearls...
in suspension from longlines in the open water. The movement towards hatchery
Hatchery
A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled conditions; alternatively, it may be for economic reasons A hatchery is a...
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
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
seed. The Japanese oyster drill (Ocenebra japonica), flatworm (Pseudostylochus osterophagus), and parasitic copepod (Mytlilcola orientalis) have been introduced accidentally to aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
areas, and have had serious impacts on oyster production, particularly in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
and Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
.
Broodstock
Pacific oyster broodstockBroodstock
Broodstock, or broodfish, are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and fry numbers. These are generally kept in ponds or tanks in which...
in hatcheries are kept in optimum conditions so the production of large amounts of high quality eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
and sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
can be achieved. Pacific oyster females are very fecund
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
, and individuals of 70-100g live weight can produce 50-80 million eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
in a single spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
. Broodstock
Broodstock
Broodstock, or broodfish, are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and fry numbers. These are generally kept in ponds or tanks in which...
adults are held in tanks at 20-22°C, supplied with cultured algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and with salinities
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
of 25-32‰. These individuals can be induced to spawn by thermal shock treatment. Yet, it is more common for the eggs from a small sample
Sample (statistics)
In statistics, a sample is a subset of a population. Typically, the population is very large, making a census or a complete enumeration of all the values in the population impractical or impossible. The sample represents a subset of manageable size...
of females (about 6) to be stripped from the gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s using Pasteur pipette
Pasteur pipette
Pasteur pipettes, also known as droppers or eye droppers, are used to transfer small quantities of liquids. They are usually glass tubes tapered to a narrow point, and fitted with a rubber bulb at the top. The combination of the Pasteur pipette and rubber bulb has also been referred to as a teat...
s and fertilized by sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
from a similar number of males.
Larval and postlarval culture
Pacific oysters have a pelagicPelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
veliger
Veliger
A veliger is the planktonic larva of many kinds of marine and freshwater gastropod molluscs, as well as most bivalve mollusks.- Description :...
larva
Larva
A larva 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
Hatchery
A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled conditions; alternatively, it may be for economic reasons A hatchery is a...
, they are kept at temperatures of 25-28°C with an optimum salinity between 20 and 25‰. Early stage veliger
Veliger
A veliger is the planktonic larva of many kinds of marine and freshwater gastropod molluscs, as well as most bivalve mollusks.- Description :...
s (<120 nm shell length) are fed daily with flagellate
Flagellate
Flagellates are organisms with one or more whip-like organelles called flagella. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla. Flowering plants do not produce flagellate cells, but ferns, mosses, green algae, some gymnosperms and other closely related plants...
algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
(Isochrysis galbana or Pavlova lutherii) along with diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
(either Chaetoceros calcitrans or Thalassiosira pseudonana). The larva
Larva
A larva 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...
e are close to a settlement stage when dark eye spots and a foot develop. During this time, settlement materials (cultch
Oyster farming
Oyster farming is an aquaculture practice in which oysters are raised for human consumption. Oyster farming most likely developed in tandem with pearl farming, a similar practice in which oysters are farmed for the purpose of developing pearls...
), such as roughed PVC sheets, fluted PVC pipes, or shells, are placed into the tanks to encourage the larvae to attach and settle. It is common, however, particularly in on the US West Coast, for the mature larvae to be 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 estuarineEstuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
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
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
supply or are enriched with nutrients from fertilizers.
Ongrowing techniques
This stage of oysterOyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
culture is almost completely sea-based. A range of bottom, off-bottom, suspended and floating cultures are used. The type of technique used depends on site-specific conditions, such as tidal range, shelter, water depth, current flow and nature of substratum
Substratum
In linguistics, a stratum or strate is a language that influences, or is influenced by another through contact. A substratum is a language which has lower power or prestige than another, while a superstratum is the language that has higher power or prestige. Both substratum and superstratum...
. Pacific oysters take 18– 30 months to develop to the market size of 70-100g live weight (shell
Mollusc shell
The mollusc shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes...
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‰.
General production
In 2000, the Pacific oyster accounted for 98% of the world’s cultured oyster production, and is produced in countries all over the world.Production statistics
Global Pacific oyster production has increased from about 150 tonneTonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s in 1950 to a peak of 750 tonnes in 1980. By 2003, global production had increased to 4.38 million tonnes. The majority was in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, which produced 84% of the global production. Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and the Republic of Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
also contributed, producing 261 000, 238 000 and 115 000 tonnes produce, respectively. The other two major producers are the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
(43 000 tonnes) and Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
(23 000 tonnes). In 2003, global Pacific oyster production was worth $ 3.69 billion, with Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
contributing over half of this amount.
Virus management
Pacific oysters are nonspecific filter feederFilter feeder
Filter feeders are 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 feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
s, which means they ingest any particulate matter in the water column. This presents major issues for virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
management of open water shellfish
Shellfish
Shellfish is a culinary 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 environments, some kinds are found only in freshwater...
farms, as shellfish like the Pacific oyster have been found to contain norovirus strains which can be harmful to humans. Globally, noroviruses are the most common cause of nonbacterial gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
, and are introduced into the water column by faecal
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
matter, either from sewage
Sewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...
discharge or land runoff from nearby farmland. Numerous gastroenteritis outbreaks in the world have been directly caused by the consumption of shellfish
Shellfish
Shellfish is a culinary 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 environments, some kinds are found only in freshwater...
from polluted areas.
Heavy metal pollution
Pacific oysters, like other shellfish are able to remove heavy metalsHeavy metals
A heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight,...
, such as zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
and copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, as well as biotoxins
Toxin
A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
(microscopic toxic phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
), from the surrounding water. These can accumulate in the tissues of the animal and leave it unharmed (bioaccumulation
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
). However, when the concentrations of the metals or biotoxins are high enough, shellfish poisoning
Shellfish poisoning
There are four syndromes called shellfish poisoning, which share some common features and are primarily associated with bivalve molluscs...
can result when they are consumed by humans. High copper concentration in Pacific oyster can be recognised by the meat turning a grass-green colour. Most countries have strict water regulations and legislation to minimise the occurrence of such poisoning cases.
Diseases
| Disease | Agent | Type | Measures |
| Denman Island disease | Mikrocytos mackini | Protozoan parasite | Restricted modified culture practices |
| Nocardiosis | Norcardia crassoteae | Bacterium | Modified culture practices |
| Oyster velar virus disease (OVVD) | Unknown | Virus | None known |
| Herpes-type virus disease of C.gigas larvae | Unknown | Virus | None |
Predators
Numerous predators of the Pacific oyster are known to damage oyster stocks. Several crab species (Cancer magister, Cancer productus, Cancer gracilis), oyster drills and starfish species (Pisater ochraceus, Piaster brevispinus, Evasterias troschelii and Pycnopodia helianthoides) can cause severe impacts to oyster culture.Productivity
ProductivityProductivity (ecology)
In ecology, productivity or production refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface per unit time, for instance grams per square metre per day. The mass unit may relate to dry matter or to the mass of carbon generated...
of the Pacific oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
can be discussed 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
Biotic component
Biotic components are the living things that shape an ecosystem. A biotic factor is any living component that affects another organism, including animals that consume the organism in question, and the living food that the organism consumes. Each biotic factor needs energy to do work and food for...
factors, such as mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...
, growth
Growth
Growth refers to an increase in some quantity over time.The quantity can be:*Physical *Abstract ....
, and oyster size, as well as the quality of the seed and the growing technique used (off bottom, bottom, suspended or floating culture). The four main causes of mortality in the Pacific oyster, these are:
- Natural mortality
- AgeAgeAge may refer to:* Age , an aspect of mathematical model theory* Age , an international peer-reviewed journal operated by Springer.* The Age, a daily newspaper published in Melbourne, Australia* Agé, a god* Åge, a given name...
- Predators
- DiseaseDiseaseA disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
- Environmental conditions (ice, freak winds)
- Age
- CompetitionCompetitionCompetition is a contest between individuals, groups, animals, etc. for territory, a niche, or a location of resources. It arises whenever two and only two strive for a goal which cannot be shared. Competition occurs naturally between living organisms which co-exist in the same environment. For...
for space: crowding of cultch - Silting: sediment runoff from land
- Cluster separation: process of breaking up clusters of oysters to into as many individual oysters as possible.
Aquaculture in New Zealand
In New ZealandNew Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, the Pacific oyster was unintentionally introduced in 1950s, most likely through ballast
Sailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...
water and from the hulls of ships. Aquaculture farmers at the time noticed the Pacific oyster outcompeted the endemic species, rock oyster (Saccostrea commercialis), which naturally occurs in intertidal areas in the North Island. 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 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in most areas, and constantly was attaching to the rock oyster collection sticks. A few years later, Pacific oysters were the dominant oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
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
Marlborough Sounds
The Marlborough Sounds are an extensive network of sea-drowned valleys created by a combination of land subsidence and rising sea levels at the north of the South Island of New Zealand...
, 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 speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
along with king salmon
Chinook salmon
The Chinook salmon, Oncorhynchus tshawytscha, is the largest species in the pacific salmon family. Other commonly used names for the species include King salmon, Quinnat salmon, Spring salmon and Tyee salmon...
and the greenshell mussel
New Zealand green-lipped mussel
The New Zealand green-lipped mussel, is a bivalve mollusc in the family Mytilidae. P. canaliculus has great importance as a cultivated species for New Zealand.-Distribution:Perna canaliculus has a wide distribution which covers all of New Zealand's mainland. P...
s. Pacific oyster aquaculture production has grown from an export value of $11 million in 1986 to $32 million in 2006. In 2006, there were 23 Pacific oyster farms throughout New Zealand, which cover a total of 750 hectares of marine space and produce 2,800 tonnes of product per year. Annual production is now between about 3,300 and 4,000 tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s. In 2005, the value of New Zealand's Pacific oyster production was $12 million domestically, and $16.9 million for export. New Zealand’s main export markets are Japan, Korea, the US, the EU and Australia.
External links
- Crassostrea gigas, Food and Agriculture Organization of the United Nations
- Pacific oyster, United States National Oceanic and Atmospheric AdministrationNational Oceanic and Atmospheric AdministrationThe National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
- http://findarticles.com/p/articles/mi_m0QPU/is_2_24/ai_n15384489
- http://www.stefannehring.de/downloads/142_Nehring-2003_Aliens-17_pacific-oyster.pdf