Clams are bivalve mollusks, so they have a hinged shell like mussels, oysters, and scallops. Natives of the North American Atlantic coast, hard clams have been introduced to the Gulf of Mexico. For farming purposes, they have also been introduced to Washington and California as well as Europe and Asia. Clams have slow growth rates and live 12-20 years on average, but can live up to 40 years. Female clams produce 1–5 million eggs per spawning event, with numerous events occurring per year. Hard clams are reproductively mature at approximately 1 year of age.Clams completely burrow into the sediment on the ocean floor, leaving only the incurrent and excurrent siphons exposed for feeding. Clams are suspension feeders, meaning that they get their food from particles suspended in the water column. Because of this, they are highly efficient at removing excess nutrients from ecosystems in the form of microscopic algae, so they contribute to a high level of water quality in the surrounding area.