CLAM, MANILA, SHORT-NECKED OR RIBBED CARPET SHELL

BIOLOGY A bivalve mollusc with distinctive black and white shell markings, it is native to the waters of east Asia. Now widespread throughout the western world, with introductions made accidentally with oysters into North America, and deliberately as hatchery broodstock into Europe. In the wild it is found burrowing on coarse sediment in intertidal waters. Matures at about 2 years, with a corresponding shell size of about 20 mm. Maximum size about 65-75 mm. Spawning occurs in summer months. ADVICE All Manila clams in the UK are progeny of broodstock imported from the west coast of USA. They are grown in trays on trestles in the sea before planting out in ground plots or seabed. Only a small number of manila clams are farmed for the table in UK (6 tonnes, 2004), the biggest production is seed for ongrowing. Clams may be harvested by manual digging or raking, or by mechanical methods e.g. suction or hydraulic dredge. Manual harvesting methods cause less disturbance to sediment than mechanical methods. Shellfish farming is an extensive, low-impact method of mariculture and high quality water standards are required for cultivation of shellfish for human consumption. When buying any farmed fish, including shellfish, ask your fish supplier if they have a buying policy that ensures high environmental farming standards are required.