About two thirds of the dollars come from Greenshell mussels, New Zealand's trade-marked brand of farmed native green-lipped mussels. They are grown suspended on submerged ropes by more than a thousand farms, covering more than 11,000 hectares of sea around our shores.
The main Greenshell mussel farming areas are in the top of the South Island, in Golden and Tasman Bays, and the Marlborough Sounds, and the Coromandel in the 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.
Aside from their visual impact, the farms also deposit shell and other waste into the water and seabed nearby, consume plankton from the ocean and have been known to cause tangling problems for whales and other marine mammals. But recently the effects have not been so severe as to raise the ire of environmental groups or widespread public concern.
New Zealand is the world's largest producer of king salmon, chiefly exported to the United States, Japan and Australia. The fish are born in land-based hatcheries and transferred to sea cages or fresh water farms for up to 18 months, until they reach a harvest weight between 2-4kg. Most sea cage farming is in the Marlborough Sounds, Stewart Island and Akaroa Harbour, and there are also fresh water operations in Canterbury, Otago and Tasman.
The absence of any native salmon species, as well as New Zealand's rigorous bio-security measures, means that the king salmon raised here don't require vaccines and antibiotics. The salmon are fed specially formulated fishmeal pellets, which do not contain steroids or other growth enhancers.
According to the New Zealand Salmon Farmers Association's Finfish Aquaculture Environmental Code of Practice states that raw material for fish feeds should come from sustainably managed fisheries.
Done badly, fish farms can create severe impacts on the seas around them, especially through the resulting faeces and uneaten food that can pollute the water and seabed. As a result, salmon farms are generally not approved if they are proposed over reefs or complex habitats with a high diversity or abundance of species, or important fish spawning or nursery habitats.
In fact, farm site selection is so critical that only a handful of sites around the country are considered suitable.?But done well, fish farms can have a potentially positive effect, as the farms tend to attract wild fish around them because of the increased shelter and nutrients.
Carefully chosen sites with strong currents ensure the cages are well oxygenated and flushed of waste. Computer controlled feeding and video monitoring has also been installed in some fish farms to reduce food waste, the resulting cost to the environment and the farms' bottom line.
Kiwi ?culture
The combination of our relatively pollution free coastlines and these developments have led to New Zealand salmon farming's recognition as the world's greenest by the Global Aquaculture Performance Index, a project of the Seafood Ecology Research Group (SERG) at the University of Victoria in Canada.
Further afield, global standards for sustainable aquaculture are currently being finalised. It is hoped this will lead to the worldwide promotion of an Aquaculture Stewardship Council certification scheme.
This would be similar to those already in place for wild fish under the Marine Stewardship Council and wood products under the Forest Stewardship Council.
The mussel farming industry is worth about $200m a year to New Zealand.
