Eggs hatch into free swimming larvae then settle to the bottom as juveniles or spat after several weeks. The time of spawning varies with currents and temperatures. Food and Growth Cockle clams are filter feeders, straining phytoplankton through their gills. Major predators include sea stars, birds, and humans. Marine fishes prey on juvenile clams.
Age is determined by counting winter growth checks on the shell.
Cockles average three to four years of age and are usually are not more than seven years old, but may reach 15 years. Age of maturity is two years at about 50-70 mm. Cockles are usually not more than 100 mm in length but can reach 120 mm. There is a great variation in size at any age and is particularly noticeable in the first year. Growth in northern latitudes is slower than in southern latitudes, probably due to decreasing mean air temperature with increasing latitude.