Natural England - Native oyster

Native oyster

Ostrea edulis

Native oyster © Paul Kay

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

Flat oyster, common oyster, edible oyster

Brief description of 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.