Marine Aquaculture
Marine aquaculture occurs in the sea, generally in the calm embayments of the coastal marine area such as the Firth of Thames and the Marlborough Sounds.
The main marine aquaculture activities in New Zealand are the farming of Greenshell™ mussels (Perna canaliculus), Pacific oysters (Crassostrea gigas), and king (or quinnat) salmon (Oncorhynchus tshawytschca).
Mussel aquaculture
The main mussel farming areas are in the top of the South Island (Golden and Tasman Bays, and the Marlborough Sounds) and the Coromandel (Firth of Thames). There are other smaller areas of mussel farming around New Zealand including Houhora Bay (Northland), the Hauraki Gulf (Auckland), as well as around Banks Peninsula and Stewart Island.
The farming method for mussels usually consists of floating backbones from which continuous looped longline ropes carrying mussels are suspended. Farms are generally located in sheltered to semi-sheltered areas where there is sufficient depth of water at low tide to keep the longline droppers off the bottom.
In recent years there has been research into offshore mussel farming in exposed areas up to several kilometres from shore. Farms in these areas, such as the farms offshore from Napier and Opotiki, use longlines suspended from backbones that are anchored up to 10 m below the water surface.
There are about 898 mussel farms in New Zealand covering a total of roughly 6535 hectares (as of December 2005). Which in 2004, generated an export market revenue of $141,400,000 (NZ$ FOB) contributing to a total market revenue of $181,400,000 (in NZ$).
Pacific oyster aquaculture
The main Pacific oyster farming areas are located in sheltered bays and harbours around the North Island. In particular, Pacific oyster farming takes place in the Whangaroa, Mahurangi, and Kaipara Harbours as well as the Coromandel and the Bay of Islands.
The farming method for Pacific oysters consists of wooden racks to which the oysters are attached. The racks are anchored in the lower intertidal region.
There are about 236 Pacific oyster farms in New Zealand covering a total of around 928 hectares (as of December 2005). Which in 2004, generated export market revenue of $14,000,000 (NZ$ FOB) contributing to a total market revenue of $26,000,000 (NZ$).
King salmon aquaculture
The main king salmon farming areas are in South Island waters. King salmon are grown in sea cages in the marine environment and in freshwater raceways. Sea cages are located in the Marlborough Sounds, Akaroa Harbour and Stewart Island. Freshwater raceways are located in several Canterbury rivers including the Clutha and Waimakariri Rivers.
The farming method for king salmon in the sea uses large floating cages moored to the sea floor. Each cage contains several thousand salmon, which are grown from smolt to a weight of around 3.5 to 4 kg.
The farming method for king salmon in freshwater uses cages placed in rivers. In the Mackenzie Basin salmon farms have been established in hydroelectric canals. Smolt from hatcheries are placed in the cages and raised to a weight of between 2 to 4 kg.
There are about 29 salmon farms in New Zealand covering a total of around 128 hectares (as of December 2005). These 29 farms account for roughly half of the worldwide farmed king salmon production. In 2004, king salmon generated export market revenue of $36,000,000 (NZ$ FOB) contributing to a total market value of $81,000,000 (NZ$).