A cockle is an edible, marine bivalve mollusk. Although many small edible bivalves are loosely called cockles, true cockles are species in the family Cardiidae. True cockles live on sandy, sheltered beaches throughout the world. The distinctive rounded shells are bilaterally symmetrical and are heart-shaped when viewed from the end. Numerous radial, evenly spaced ribs are a feature of the shell in most but not all genera.
Cockles are a popular type of edible shellfish in both Eastern and Western cooking. They are collected by raking them from the sands at low tide. However, collecting cockles is hard work, and, as seen from the Morecambe Bay disaster, 23 people died, which can be dangerous if local tidal conditions are not carefully watched.
Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of mollusks, crustaceans, and echinoderms.
Although most kinds of shellfish are harvested from saltwater environments, some are found in freshwater. Shellfish are among the most common food allergens.