Native oyster
Ostrea edulis
Native oysters have a rough shell that is
yellow, pale green or brown in colour, sometimes with bluish, pink
or purple markings. The two halves of a native oyster’s shell are
different shapes. One value is a deep cup and is cemented to
the seabed, while the other is very flat and forms a lid.
Individual oysters can vary widely in shape too, especially when
crowded together in dense beds.
The shell shape is a good way to distinguish
native oysters from Pacific oysters, which were introduced to the
UK in 1926, and which compete with the native oyster for space and
food. Native oysters have rounder shells with smoother edges,
while their Pacific relatives have a more elongated shell with
deeply grooved edges.
All native oysters start out as males, and
throughout their lives change back and forth from male to
female. A single female oyster can produce 2 million
eggs.
Although usually up to about 11cm long,
native oysters can grow to more than 20cm and can live as long as
20 years.
Native oysters can be found down to a depth of 80m on just about
any type of seabed from bedrock to mud. They are also
tolerant of wide range of wave and tidal conditions, and live in
sheltered bays as well as exposed coasts. They can tolerate
the reduced salinity that occurs when fresh and seawater mix, and
so can be found in estuaries.
Other common names
Common oyster
Edible oyster
Flat oyster
European distribution
The native oyster is widely distributed around UK coasts,
particularly in the south and west, with the main stocks found in
the south-east, the Thames estuary, the Solent and the River
Fal. Its wider European range extends from the Norwegian Sea
to the Atlantic coast of Morocco, and into the Mediterranean and
Black Sea.
Conservation status/need
This is a UK BAP Priority Species (BAP
species are now Species of Principal Importance/Priority
Species).- Species of principal importance for the purpose of conservation
of biodiversity under the Natural Environment and Rural Communities
Act 2006
- OSPAR List of Threatened and/or Declining Species and Habitats
(Region II - Greater North Sea and Region III - Celtic Sea)
Further information
JNCC - UK BAP Priority
Species and Habitats
OSPAR List of Threatened and/or Declining Species and
Habitats
OSPAR Commission –
Background Document for Ostrea edulis and Ostrea
edulis beds
Biodiversity Action Reporting System
Food
and Agriculture Organisation
Marine
Life Information Network
Marine Species Identification Portal