- A very common bivalve mollusc (various species) found worldwide usually attached to rocks near the water line, but some bury themselves in the sand. Most have dark blue to black shells up to 8 cm long, but some from New Zealand have blue and green shells. Generally sold live in their shells or removed, cooked and preserved in brine, sauce or by canning. Sometimes sold smoked. Cooked as any other mollusc. The mussel is a highly productive shellfish producing up to 10000 kg of meat per hectare per year. Varieties include the common mussel, green-lipped mussel, horse mussel and fan mussel.