The common cockle (Cerastoderma edule ) is a species of edible saltwater clam, a marine bivalve mollusc in the family Cardiidae, the cockles. It is found in waters off Europe, from Iceland in the north, south into waters off western Africa as far south as Senegal. The ribbed oval shells can reach 6 centimetres (2.4 in) across and are white, yellowish or brown in colour. The common cockle is harvested commercially and eaten in much of its range.
It typically reaches from 3.5 centimetres (1.4 in) to 5 centimetres (2.0 in) in length, but sometimes it reaches 6 centimetres (2.4 in). The shells are pale or whitish yellow, grubby white, or brown. The shell is oval, and covered by ribs, which are flattened in the middle part of the shell. The digestive glands are light brown to dark green.
In contrast, the similar lagoon cockle has an elongated shell posteriorly, black digestive glands and is found in substrate of stagnant water.
This species is found in coastal areas of the northern and eastern Atlantic Ocean. It is widely distributed from Iceland and Norway in Europe, to Senegal along the coast of west Africa. The common cockle is one of the most abundant species of molluscs in tidal flats located in the bays and estuaries of Europe. It plays a major role as a source of food for crustaceans, fish, and wading birds.
This species is a filter feeder, meaning that it feeds by straining water to obtain suspended matter and food particles. Water is inhaled through an inhalant siphon, and exhaled through an exhalant siphon.
It tolerates a wide range of salinity (euryhaline), and wide range of temperatures (eurythermic), which helps to explain its very extensive range. It has a first spawning period in early summer, and a second one in the fall. Lifespan is typically five to six years, though it may perish earlier due to predation by humans as well as crabs, flounder, and various birds especially including oystercatchers. A green shore crab (Carcinus maenas ) can consume up to 40 common cockles a day, eating smaller cockles (under 1.5 cm diameter) much more quickly than larger ones. Hence they could have a greater impact in lean seasons where cockles did not grow so quickly.
