Page 1 – Green-lipped mussels
Aquaculture in New Zealand
Green-lipped mussels, quinnat salmon and Pacific oysters are the backbone of New Zealand’s aquaculture industry and are significant export items.
With its long coastline bathed in cool ocean waters, New Zealand is ideally suited to a diverse aquaculture. New Zealand aquaculture is not restricted to the farming of fish, but also includes the rearing and cultivation of shellfish (molluscs), prawns, crabs and crayfish (crustaceans), sea cucumbers (echinoderms), sponges, seaweeds (algae) and watercress.
Aquaculture can occur in coastal waters, rivers, lakes, and on land – in excavated pools or specially constructed tanks.
From small beginnings in the 1960s, New Zealand aquaculture has become a multi-million-dollar industry. Since the 1980s it has been the country’s fastest growing rural business. By 2001 aquaculture produce was worth $280 million.
Giant Malaysian river prawns (Macrobrachium rosenbergii) have been commercially farmed in Taupō since 1991. The prawn farm uses waste water from the nearby Wairākei geothermal power plant to heat fresh water to temperatures between 24º and 28º C. Caring for the omnivorous crawlers is labour intensive, as they go through a series of moults before they are harvested at nine months of age. All 17 tonnes of annual harvest is consumed in New Zealand.
Mussels were harvested by hand from intertidal rocks until the 1960s, when a dredge industry attempted to satisfy local demand. However, mussel beds in Tasman Bay (Nelson region) and the Hauraki Gulf (Coromandel region) were quickly dredged out, so a few people turned their attention to mussel culture. The native green-lipped mussel (Perna canaliculus) was used to trial a cultivation technique in which young mussels (mussel spat) were grown on ropes suspended from rafts. The sheltered, clean waters of the Hauraki Gulf and the Marlborough Sounds, rich in nutritious plankton, provided an ideal environment. After 12–18 months the cultured mussels were ready for harvest, and the first went on sale in 1971.
As more growers entered the industry, the labour-intensive raft method of cultivation was dropped in favour of a modified Japanese longline system. Biodegradable stockings full of spat are tied to parallel rows of looped ropes, supported by buoys. The young mussels grow through the stockings and anchor themselves to the ropes with threads formed by a special secretion.
For some years, ropes were reseeded after harvest with spat found growing naturally in coastal waters. This proved risky, however, as the timing and volume of supply was unpredictable. In 1974 a marine scientist discovered abundant mussel spat attached to washed-up seaweed on Ninety Mile Beach, Northland. Local people began to collect the seaweed, pack it into buckets, and air freight it to mussel farmers. Kaitāia spat, as it was called, became the main source of seed mussels in New Zealand.
During the 1970s mussels had been exported to the United States as a powdered health supplement to relieve arthritis symptoms. This market collapsed overnight in 1981, when stringent US drug legislation controls were placed on the powder. Subsequently, extracts from mussels were developed in New Zealand, where they continue to be marketed as health products.
In the mid-1980s fresh green-lipped mussels were cheap and plentiful in New Zealand supermarkets, and the industry turned its attention to developing reliable export markets.
Frozen mussels in half shells became the dominant export item, patented with the trade name NZ Greenshell Mussels. By 2000 the industry was booming: mussels were New Zealand’s second most important seafood export, with sales of $170 million to over 60 countries. About 1,500 people were directly involved with mussel production on marine farms located predominantly in the Marlborough and Coromandel regions.