The green mussel is native to New Zealand, which has exported it to the United States since 1979. Greenshells are farmed mussels, cultivated on ropes, rafts or longlines. Growing standards, including water quality and production levels, are tightly regulated by the New Zealand government, so quality of the product is consistently high. Green mussels boast an attractive, elongated shell that is brownish-green on one end but changes to green at its broad lip, interrupted by dark-brown striations. The mussels grow to over 8 inches, though market size is usually 3 1/2 to 4 inches. Upon harvesting, live mussels are typically cooled to about 36°F and held at that temperature throughout the shipping process. Prior to shipping, their shells are cleaned and, in high-end operations, they are hand-graded and packed within hours of harvest. Look for the grower’s name on the mussels — a dependable sign of safety and high quality.