Ostrea edulis

Researched By	Angus Jackson	Data Supplied By	MarLIN
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Ostrea edulis	Common name	Native oyster
MCS Code	W1758	Recent Synonyms	None
Phylum	Mollusca	Subphylum
Superclass		Class	Pelecypoda
Subclass		Order	Ostreoida
Suborder	Ostreina	Family	Ostreidae
Genus	Ostrea	Species	edulis
Subspecies
Additional Information	Also commonly known as the flat oyster and European oyster.
Taxonomy References	Howson & Picton, 1997, Hayward & Ryland, 1995b, Campbell, 1994, Christensen, 1980, Anonymous, 1999(b), Tebble, 1966, Yonge, 1960, Korringa, 1952
General Biology
Growth form	Bivalved	Feeding method	Active suspension feeder
Mobility/Movement	Permanent attachment	Environmental position	Epifaunal
Typical food types	Suspended organic particles.	Habit	Attached
Bioturbator	Not relevant	Flexibility	None (< 10 degrees)
Fragility	Robust	Size	Small-medium(3-10cm)
Height	Insufficient information	Growth Rate	Insufficient information
Adult dispersal potential	None	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	There is some evidence that reduced growth, weight and poor conditions are a consequence of high population densities (300 per square yard). Size and shape can be extremely variable. Because the oyster cements itself to the substratum, growth of neighbouring individuals may result in competition or space and distort the usual shell shape. Feeding is carried out by pumping water through a filter in the gill chamber removing suspended organic particles. The native oyster starts life as male, becoming mature at around 3 years of age. After spawning the oyster becomes a functional female. Larvae are seldom produced by oysters under 50 mm. Growth is quite rapid for the first year and a half. It then remains constant at around 20 grams per year before slowing down after five years. In the British Isles, the main growing season is from April to October. The oyster faces serious competition from the introduced species Crepidula fornicata, the slipper limpet. Brought over from the United States this species can occur in very high densities competing for space and food. The slipper limpet deposits pseudo faeces which forms 'mussel mud' changing the substratum and hindering settlement. Native oysters are preyed on by a variety of species including starfish and Ocenebra erinacea, the sting winkle or rough tingle. Buccinum undatum, the common whelk also feeds on oysters but not as exclusively as the sting winkle. Urosalpinx cinerea, the American oyster drill was accidentally introduced to the British Isles with American oysters. This species lives on oyster beds and feeds almost entirely on oyster spat.
Biology References	Lilley, 2000, Dare, 1982, Sheldon, 1968, Richardson et al., 1993, Askew, 1972, Hutchinson & Hawkins, 1992, Yonge, 1960, Korringa, 1952
Distribution and Habitat
Distribution in Britain & Ireland	Widely distributed around the British Isles but less so on the east and north-east coasts of Britain and Ireland. The main stocks are now in the west coast of Scotland, the south-east and Thames estuary, the Solent, the River Fal, and Lough Foyle.
Global distribution	Found naturally from the Norwegian Sea south through the North Sea down to the Iberian Peninsula and the Atlantic coast of Morocco. Found in the Mediterranean Sea and extends into the Black Sea.
Biogeographic range	Not researched	Depth range	0-80m
Migratory	Non-migratory / Resident
Distribution Additional Information	The native oyster has also been introduced and is cultivated in North America, Australia and Japan. Cultivated populations may be encouraged through the use of an artificial substratum (limed tiles) used preferentially for larval settlement. Oysters are found on a wide variety of substrata but typically where the seabed is hard. Can form into dense 'beds' of oyster shells.
Substratum preferences	Large to very large boulders, Small boulders, Cobbles, Pebbles, Gravel / shingle, Artificial (e.g. metal/wood/concrete), Muddy gravel, Muddy sand, Mud, Bedrock	Physiographic preferences	Open coast, Sealoch, Ria / Voe, Estuary
Biological zone	Lower Eulittoral, Sublittoral Fringe, Upper Infralittoral, Lower Infralittoral, Upper Circalittoral, Lower Circalittoral	Wave exposure	Exposed, Moderately Exposed, Sheltered, Very Sheltered, Extremely Sheltered
Tidal stream strength/Water flow	Insufficient information	Salinity	Full (30-40 psu), Variable (18-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	I
Distribution References	Hayward & Ryland, 1995b, Campbell, 1994, Anonymous, 1999(b), Tebble, 1966, Lilley, 2000, Yonge, 1960, Korringa, 1952, Moore, 2002
Reproduction/Life History
Reproductive type	Protandrous hermaphrodite	Developmental mechanism	Planktotrophic
Reproductive Season	June to September	Reproductive Location	As adult
Reproductive frequency	Annual protracted	Regeneration potential	No
Life span	6-10 years	Age at reproductive maturity	3-5 years
Generation time	Insufficient information	Fecundity	Up to 2,000,000 in large females
Egg/propagule size	ca 150 µm diameter	Fertilization type	Internal
Larvae/Juveniles Larval/Juvenile dispersal potential >10km Larval settlement period Insufficient information Duration of larval stage 11-30 days
Additional Information	A life span of 5-10 years is probably typical (majority of individuals in populations are 2-6 years old). However, they may reach in excess of 15 years old. Oysters are protandrous alternating hermaphrodites. This means that they start off as males producing sperm then switch to egg producing females, back to males and so on. Gamete maturation begins in March or April and is in part temperature dependent. Gametogenesis may be continuous in warmer conditions e.g. California. On the west coast of Ireland there is at least one spawning in each sexual phase during the summer. There may be some periodicity in spawning with peaks during full moon periods. Fecundity may be as high as 2,000,000 in large individuals. The eggs are around 150 microns in diameter. Eggs produced during the female stage are held in the gills and mantle cavity. The eggs are fertilized by sperm drawn in by the inhalant water flow used for feeding and respiration. The fertilized eggs are retained for 7-10 days for the early development until the veliger stage is reached. This is sometime called larviparous or incubatory development.
Reproduction References	Lilley, 2000, Dare, 1982, Orton, 1936, Wilson & Simons, 1985, Yonge, 1960, Korringa, 1952