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 a ...
native to the
Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
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 area ...
. 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 ...
in
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 the C ...
,
Australia,
Europe, 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 country ...
.
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 East ...
and its specific epithet ''gígās'' is from the Greek for "giant". It was previously placed in the genus ''
Crassostrea
''Crassostrea'' is a genus of true oysters (family Ostreidae) containing some of the most important oysters used for food. Some species in the genus have been moved to the genus '' Magallana''.
Species Extant species
Extant species include ...
''; from the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''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, a city
**Worms (electoral district)
*Worms, Nebraska, U.S.
*Worms im Veltlintal, the German name for Bormio, Italy
Arts and entertainme ...
,
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 simple polygon that is not convex is called concave, non-convex or ...
. 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 Taxonomy (biology), 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 ...
, 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 of ...
and
subtidal
The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth.
From the point of view of marine biology it forms a relatively stable and well-illuminated ...
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.
Th ...
often settle on the shell of adults, and great masses of
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 a ...
s can grow together to form
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 a ...
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](_blank)
Food and Agriculture Organization of the United Nations (FAO) The Pacific oyster is also a very temperature tolerant
species
In biology, a species is the basic unit of Taxonomy (biology), 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 ...
, 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 ...
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 sperm ...
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
Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...
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 devia ...
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 aquati ...
in the Pacific oyster occurs at 20 °C.
This species is very
fecund
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
, 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 aquati ...
.
Once released from 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 sperm ...
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 are ...
s), are then pushed through the
gill
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
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.
Th ...
of the Pacific oyster are
planktotrophic, and are about 70 µm at the
prodissoconch
A prodissoconch (meaning first or earliest or original shell) is an embryonic or larval shell which is present in the larva of a bivalve mollusk (clams, scallops, oysters, etc.). (The homologous structure in gastropods (snails) is called the pr ...
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
Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...
and settle as small
spat.
Similar to other oyster
species
In biology, a species is the basic unit of Taxonomy (biology), 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 ...
, 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
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
, and occurs primarily in temperate waters between 30° N and 48° N. It is now the most widely farmed and commercially important
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 a ...
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 primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
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.
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 ad ...
, where it is outcompeting native species, such as the
Olympia oyster
''Ostrea lurida'', common name the Olympia oyster, after Olympia, Washington in the Puget Sound area, is a species of edible oyster, a marine bivalve mollusk in the family Ostreidae. This species occurs on the northern Pacific coast of North Am ...
in
Puget Sound, Washington; the rock oyster, ''
Saccostrea commercialis'', in the North Island of
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 country ...
; and the blue mussel, ''
Mytilus edulis
The blue mussel (''Mytilus edulis''), also known as the common mussel, is a medium-sized edible marine bivalve mollusc in the family Mytilidae, the mussels. Blue mussels are subject to commercial use and intensive aquaculture. A species with a ...
'', 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
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 a ...
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
A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish, poultry or even turtles. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled condi ...
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 and
Europe.
Broodstock
Pacific oyster
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.Waples ...
s in hatcheries are kept in optimum conditions so the production of large amounts of high quality
eggs
Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
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, wh ...
can be achieved.
Pacific oyster females are very
fecund
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
, and individuals of 70–100 g live weight can produce 50–80 million
eggs
Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
in a single
spawn.
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 photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
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 to ...
of 25–32 ppt.
These individuals can be induced to spawn by thermal shock treatment.
Yet, the eggs from a small
sample of females (about six) are more commonly stripped from 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 sperm ...
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
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, wh ...
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 wa ...
veliger
A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells.
Description
The veliger is the characteristic larva of the gastropod, bivalve and scaphopod ta ...
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.
Th ...
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'' 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'' or ''
Thalassiosira pseudonana
''Thalassiosira pseudonana'' is a species of marine centric diatoms. It was chosen as the first eukaryotic marine phytoplankton for whole genome sequencing. ''T. pseudonana'' was selected for this study because it is a model for diatom physiolog ...
'').
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 environment ...
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
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard o ...
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 States c ...
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, 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 north ...
,
France 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
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
(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 northeast ...
(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
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
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 Ivanovsky's ...
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 enviro ...
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 deve ...
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 dehydrat ...
, and are introduced into the water column by
faecal matter, either from
sewage 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 periodic ta ...
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
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
Shellfish poisoning includes four syndromes that share some common features and are primarily associated with bivalve molluscs (such as mussels, clams, oysters and scallops.) As filter feeders, these shellfish may accumulate toxins produced by ...
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'', ''
Cancer productus'', ''
Metacarcinus gracilis''),
oyster drill
''Urosalpinx cinerea'', common name the eastern oyster drill or Atlantic oyster drill, is a species of small predatory sea snail, a marine gastropod mollusk in the family Muricidae, the murexes or rock snails.
They use chemoreception in their e ...
s, and
starfish
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...
species (''
Pisater ochraceus'', ''
Pisater brevispinus'', ''
Evasterias troschelii'', and ''
Pycnopodia helianthoides'') 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
Canoeing is an activity which involves paddling a canoe with a single-bladed paddle. Common meanings of the term are limited to when the canoeing is the central purpose of the activity. Broader meanings include when it is combined with other acti ...
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 att ...
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 dioxide ...
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 defini ...
. Overall, these effects combine to lower
recruitment
Recruitment is the overall process of identifying, sourcing, screening, shortlisting, and interviewing candidates for jobs (either permanent or temporary) within an organization. Recruitment also is the processes involved in choosing individual ...
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
Mortality is the state of being mortal, or susceptible to death; the opposite of immortality.
Mortality may also refer to:
* Fish mortality, a parameter used in fisheries population dynamics to account for the loss of fish in a fish stock throug ...
, 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'', is an oyster species belonging to the family Ostreidae.MolluscaBase eds. (2022). MolluscaBase. Saccostrea Dollfus & Dautzenberg, 1920. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/ ...
(''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 ...
species
In biology, a species is the basic unit of Taxonomy (biology), 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 ...
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 ...
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
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 States c ...
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
See also
*
Philippine cupped oyster (''Magallana bilineata'')
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) 327–333Crassostrea 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