Oysters

There are three species of oysters commonly found on Cornish shores. Two of the species are of commercial importance the Edible Oyster Ostrea edulis and the Portugese Oyster Crassostrea angulator, these are locally farmed.

Oysters have two valves, the upper valve is convex, the lower flatter. This lower valve is cemented to hard surfaces and is often distorted. The lower valve as it grows follows the shape of the surface it is cemented on.

       Edible Oyster Ostrea eduli

        Portugese Oyster Crassostrea angulato

        Common Saddle Oyster Anomia ephippium

Edible Oyster Ostrea edulis

Once abundant, but over the last century numbers have severely declined. These almost round shells are large up to 4 inches across. The outer shell has a layered pleated surface while the inner surfaces are smooth with a whitish nacre. The edible oyster throughout its life often alternates its sex, this being brought on by seasonal or water temperature changes.

Portugese Oyster Crassostrea angulator  

The shell differs from that of the edible oyster, being more elongated reaching 6 inches in length.

The shell possesses a rougher surface.

Not a native of these shores, but has been introduced to this area by oyster fisheries.

Common Saddle Oyster Anomia ephippium

The common saddle oyster is a roundish shell that can reach over 2 inches. Saddle oysters cement themselves to hard surfaces and grow to fit the surface. This often leads to distortion of the shell.

The upper valve is slightly domed.

The lower valve is flatter and has a distinctive large aperture through which the saddle oyster attaches itself.

The inside surface of both valves have a pearly lustre.