the mussel with the iridescent green lip
- Size
- Shell: 10–15 cm, Weight: 50–100 g
- Lifespan
- 10–15 years
- Diet
- Phytoplankton and organic particles. Filters food from the water using its gills. Draws water in through its siphon and extracts microscopic algae. Feeds continuously when submerged.
- Habitat
- Rocky reefs, wharf piles and mussel farms from the low tide mark down to 30 metres depth. Attaches to hard surfaces using strong byssus threads. Prefers sheltered areas with clean, nutrient-rich water and strong currents.
- Range
- Coastal waters of the North and South Islands from Northland to Stewart Island. Most common in harbours and sheltered bays. Farmed throughout the Marlborough Sounds, Coromandel and Stewart Island. Endemic to New Zealand.
- Endemism
- Endemic
- Main Threats
- Disease outbreaks are the primary threat. Climate change affecting water temperatures and ocean acidification impacting shell formation. Water quality degradation in farming areas. Storm damage to farms.
- Population
- Populations are managed through the aquaculture management system. The greenshell mussel industry is one of New Zealand's most valuable aquaculture sectors. Farmed mussels are grown on lines suspended in the water column.
- Conservation Status
- Not Threatened
New Zealand's most famous and valuable shellfish is named for the bright green lip along the edge of its shell. This green edge is a distinctive feature that sets it apart from the blue mussel found in other parts of the world. The green colour comes from a pigment in the shell that is unique to this species. It is farmed extensively in the Marlborough Sounds, Coromandel and Stewart Island, making it one of New Zealand's most important aquaculture products. Its sweet, plump flesh is exported around the world, from China to the United States.
The Maori names Kuku and Kutai are also used for the blue mussel, reflecting the similarity between the two species. Both names refer to the mussel's habit of clinging to rocks and wharf piles, a behaviour that has been observed by Māori for centuries. Greenshell mussels attach to ropes and lines in farms using strong byssus threads, growing to harvest size in 12 to 18 months. These threads are made of a protein that is both strong and elastic, allowing the mussel to withstand the force of waves and currents.
The greenshell mussel industry began in the 1970s and has grown rapidly since. Today, it is worth hundreds of millions of dollars annually. The mussels are grown on long lines suspended in the water, allowing them to feed on natural plankton without the need for artificial feed. This makes mussel farming one of the most sustainable forms of aquaculture.
Disease outbreaks are the greatest threat to the industry. In recent years, a bacterial disease has caused significant losses in some farming areas. Scientists are working to understand the disease and develop resistant strains of mussels. Climate change is also a concern. Warmer water temperatures could allow new diseases to establish, and ocean acidification could make it harder for mussels to build their shells.
The greenshell mussel is also studied for its health benefits. Research suggests that the green-lipped mussel contains compounds that reduce inflammation, making it a popular dietary supplement for people with arthritis. The mussel that feeds New Zealand also heals it.