Perna canaliculus, the New Zealand green-lipped mussel, also known as the New Zealand mussel, the greenshell mussel, kuku, and kutai, is a bivalve mollusc in the family Mytilidae (the true mussels). P. canaliculus has economic importance as a cultivated species in New Zealand. Distribution Perna canaliculus occurs around all of New Zealand's mainland. It is usually found below the intertidal zone, but it can occur in the intertidal zone. P. canaliculus feeds on various types of phytoplankton. Description This shellfish is economically important to New Zealand. It differs from other mussel species in that it has dark brown/green shells with green lips around the edges, and has only one adductor muscle. It is also one of the largest mussel species, reaching in length. Aquaculture P. canaliculus is endemic to New Zealand. When grown for aquaculture there, it is marketed under the trademark name Greenshell. This industry produces over annually and in 2009 was valued in excess of NZ$250 million. The aquaculture of the New Zealand greenshell mussel relies heavily on the production of mussel seed, or spat, by wild mussel populations. Around 270 tonnes of wild spat which is attached to beach-cast seaweed are collected from Ninety Mile Beach in northern New Zealand each year to supply the aquaculture industry. Nowhere else in the country are such large quantities of mussel-covered seaweed washed ashore. The density of spat varies from of seaweed. This single beach provides around 80% of the seed mussels required for this aquaculture industry. The remaining 20% is caught using fibrous ropes which are suspended in the sea near mussel farms. Even with this industry’s heavy dependency on wild spat, the biological and environmental processes by which the spat arrives on Ninety Mile Beach and on spat collection ropes are largely unknown. Furthermore, the amount of mussel spat that lands on Ninety Mile Beach is highly variable. This uncertainty of supply has resulted in major production problems for the industry which must endure periods up to a year without the arrival of any spat. ‘Spatfall’ events are also affected by El Niño periods and can result in delays in mussel farm production due to the insufficient seed landing on Ninety Mile Beach. New Zealand greenshell mussel cultivation began in the 1970s and has since undergone massive expansion, with production growth of 708% from 1988 to 2000 (an average annual growth of 18%). Initial farms were based on