Editing Oyster (section)

== Habitat and behaviour ==
[[File:Oyster reef Hunting Island SC.jpg|thumb|right|Oyster reef at about mid-tide off fishing pier at [[Hunting Island State Park]], South Carolina]]
A group of oysters is commonly called a bed or [[oyster reef]].
[[File:Oyster Dalian.JPG|thumb|Rocks in [[intertidal zone]] covered by oysters, at Bangchuidao Scenic Area, [[Dalian]], [[Liaoning Province]], China]]
As a [[keystone species]], oysters provide [[Habitat (ecology)|habitat]] for many marine species.
''Crassostrea'' and ''Saccostrea'' live mainly in the [[intertidal zone]], while ''Ostrea'' is [[subtidal]]. The hard surfaces of oyster shells and the nooks between the shells provide places where a host of small animals can live. Hundreds of animals, such as [[sea anemones]], [[barnacles]], and [[Ischadium recurvum|hooked mussels]], inhabit [[oyster reef]]s. Many of these animals are prey to larger animals, including fish, such as [[striped bass]], [[black drum]] and [[croakers]].

An oyster reef can increase the surface area of a flat bottom 50-fold. An oyster's mature shape often depends on the type of bottom to which it is originally attached, but it always orients itself with its outer, flared shell tilted upward. One valve is cupped and the other is flat.

Oysters usually reach maturity in one year. They are [[protandric]]; during their first year, they spawn as males by releasing [[sperm]] into the water. As they grow over the next two or three years and develop greater energy reserves, they spawn as females by releasing [[egg (biology)|eggs]]. [[Bay oyster]]s usually spawn from the end of June until mid-August. An increase in water temperature prompts a few oysters to spawn. This triggers spawning in the rest, clouding the water with millions of eggs and sperm. A single female oyster can produce up to 100 million eggs annually. The eggs become fertilized in the water and develop into larvae, which eventually find suitable sites, such as another oyster's shell, on which to settle. Attached oyster larvae are called spat. Spat are oysters less than {{convert|25|mm|in|abbr=on|0}} long. Many species of bivalves, oysters included, seem to be stimulated to settle near adult [[conspecific]]s.

[[File:Electric oyster MolluSCAN eye project.jpg|thumb|left|Pacific oyster ''Crassostrea gigas'' equipped with activity electrodes to follow their daily behaviour]]
Oysters filter large amounts of water to feed and breathe (exchange {{O2}} and {{CO2}} with water) but they are not permanently open. They regularly shut their valves to enter a resting state, even when they are permanently submersed. Their behaviour follows very strict circatidal and circadian rhythms according to the relative moon and sun positions. During neap tides, they exhibit much longer closing periods than during the spring tide.<ref>{{cite journal | url=https://pubmed.ncbi.nlm.nih.gov/21539422/ | pmid=21539422 | year=2011 | last1=Tran | first1=D. | last2=Nadau | first2=A. | last3=Durrieu | first3=G. | last4=Ciret | first4=P. | last5=Parisot | first5=J. P. | last6=Massabuau | first6=J. C. | title=Field chronobiology of a molluscan bivalve: How the moon and sun cycles interact to drive oyster activity rhythms | journal=Chronobiology International | volume=28 | issue=4 | pages=307–317 | doi=10.3109/07420528.2011.565897 | s2cid=25356955 }}</ref>

Some tropical oysters, such as the [[mangrove oyster]] in the family [[Ostreidae]], grow best on [[mangrove]] roots. Low tide can expose them, making them easy to collect.

The largest oyster-producing body of water in the [[United States]] is the [[Chesapeake Bay]], although these beds have decreased in number due to overfishing and pollution. Other large [[oyster farming]] areas in the US include the bays and estuaries along the coast of the [[Gulf of Mexico]] from [[Apalachicola, Florida]], in the east to [[Galveston, Texas]], in the west. Large beds of edible oysters are also found in Japan and Australia. In 2005, China accounted for 80% of the global oyster harvest.<ref>{{cite web
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title=China harvests almost 4 m tonnes of oyster in 2005
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access-date=12 July 2008
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archive-date=26 January 2012
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archive-url=https://web.archive.org/web/20120126052340/http://www.fao.org/figis/servlet/SQServlet?file=/usr/local/tomcat/FI/5.5.23/figis/webapps/figis/temp/hqp_30190.xml&outtype=html
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url-status=dead
}}</ref> In Europe, France remained the industry leader.

Common oyster predators include [[crab]]s, [[seabird]]s, [[starfish]], and [[human]]s. Some oysters contain crabs, known as [[oyster crab]]s.<ref>{{cite journal |last1=Christensen |first1=Aage Møller |last2=McDermott |first2=John J. |title=Life-History and Biology of the Oyster Crab, Pinnotheres ostreum Say |journal=Biological Bulletin |date=April 1958 |volume=14 |issue=2 |pages=146–179|doi=10.2307/1538845 |jstor=1538845 |s2cid=88045743 |url=https://www.biodiversitylibrary.org/part/16401 }}</ref>