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Mussel industry is alive, alive 'o
by Keith Ingram

The aquaculture industry in New Zealand has got to be one of our success stories, with the New Zealand green lip mussel being the leader. With one notable exception, every species, whether animal or vegetable, currently farmed in New Zealand to any great extent has been imported. This exception is the New Zealand green lip mussel, or, as it is now branded and registered by the mussel industry, Greenshell¨ mussel.

Perna canaliculus is a native to New Zealand and is said to be unique in that it grows nowhere else in the world. Mussels have been a staple food in New Zealand for many centuries, being traditionally eaten by Maori and then enjoyed by European settlers since their arrival.

Their wide distribution around the coast and relatively easy harvesting by handpicking made mussels accessible all year round. While several species occur naturally in our waters, the focus has always been on the green shell mussel for commercial development.
Because they are a New Zealand native, the farming of green shell mussels presents no environmental problems. The success surrounding this shellfish was all about giving Mother Nature a helping hand. By doing this, New Zealand marine farmers have developed a safe, sustainable and environmentally friendly industry with numerous community benefits.
Decades of handpicking and some years of dredging produced signs of depletion in the early 1960s, which led to consideration of cultivation as a means of ensuring continued supply. Initial attempts to cultivate mussels utilised the European raft technique, but this proved costly and cumbersome. In 1972 the New Zealand Fishing Industry Board initiated a nine-year research and development programme in the Marlborough Sounds.
This programme brought about the establishment of the Japanese longline method of cultivation, and found answers to the essential matter of regular and reliable supply of seed (spat) mussels for growing. The longline technique created a better environment for growing mussels, and at the same time improved public boat safety by removing the cumbersome and heavy raft structures. Since those early days a considerable number of innovations and refinements have been developed and put into place.
Mussel farmers have vastly improved every aspect of their operation since these early beginnings, with sweeping improvements to the longline technique, transferring spat, growing strategies and harvesting methods. Gear, equipment and vessels once copied or borrowed from other uses are now designed and manufactured in New Zealand expressly for the mussel farming industry.
Several factors govern the siting of mussel farms. Clean, unpolluted water is the most essential consideration, followed by the need to site farms in areas of relatively calm sea conditions and out of the effect of ocean swells. Care also has to be taken not to site farms where they will interfere with or impede the passage of vessels of all types. Water depth is also important, with the average farm being in depths of 5m to 30m.
Greenshell mussels prefer the warmer waters of the North Island, but grow well in the Marlborough Sounds at the top of the South Island, which, with over 500 current farm sites, is the major growing region. The next important area is around Coromandel in the Firth of Thames, and the Hauraki Gulf, followed by Stewart Island in the far south.
Since the inception of mussel farming in the late 1960s minimal ecological imbalance has been observed on or near established marine farm sites. The very small uptake of food organisms passing through the farms, as a percentage of the whole, has no adverse effect on the food chain, and therefore does not disadvantage other marine life in the vicinity.
Mussel farming is environmentally friendly. The only artificial or man-made components are the inert floats, ropes and anchors which support the mussels while they grow. There is no use whatsoever of fertilisers, herbicides or pesticides, and in that respect mussel farming is even cleaner and greener than organic gardening.
Mussels are vulnerable to predation by various species of fish throughout their growing cycle, but especially in the early stages of growth. Because the loops of growing rope are suspended well clear of the seabed, neither bottom-dwelling fish such as starfish nor fouling cause a problem.
However, a number of species, principally snapper, spotties and leatherjackets, can cause problems for growers in certain areas. For that reason, where necessary, growers attempt to site nursery ropes in predator-free areas. In most cases, and provided they take care, recreational fishers are accepted and often welcomed by the growers to tie up to the farm and fish from it. Indeed, by providing a host environment, the loaded longlines actually benefit many other marine creatures. In many, if not most, sites this provides a flow-on benefit for recreational anglers.
In terms of the shared use of the environment, regulations governing the siting of marine farms and the longline arrangement within them ensure that they do not dominate the landscape. Ample provision is made in all areas to provide ready access for all other marine users. The statutory placement of lights and navigational aids make navigation easier for boaties, especially at night. Even so, some potential problems do exist with recreational boaties over the loss of access to safe anchorages. In an effort to enable future growth, the industry is currently investigating the options of deep, open-water farms as the development of advanced anchoring and longline suspension techniques is achieved.
The vessels used for mussel farming today are a far cry from those used in the days of development in the 1960s and 1970s. The first were small launches or fishing vessels which were converted and used for every phase of the job, from collecting spat through to harvesting and delivery. The use of these small boats meant that the work was very labour-intensive, physically demanding and time-consuming.
The rapid increase in production over the past three decades, coupled with an obvious need for innovation, has seen the development of a new style of fleet in the mussel industry. Today's vessels are far removed from the small 'do everything' vessels of the past, and have become specialised in every respect.
Specially designed vessels are used for the initial setting up of longlines and anchoring gear, while fast and manoeuvrable vessels carry out longline seeding along with maintenance and inspection chores.
Harvesting, which was originally carried out by hand and then largely by towed barges, is now done by specially designed large harvesting vessels working under contract. These are fitted with a complex array of efficient, purpose-designed and labour-saving equipment.
A series of in-line mini-cranes progressively raise the very heavy mussel-laden longline to where the hydraulic stripper pares the mussels from the longline rope. The rope is automatically fed into a container bag for cleaning ashore, and ultimate re-use.
As the mussels are stripped they pass into a revolving drum. This drum, with its high-pressure water jets and revolving action, cleans and declumps the mussels, which are deposited onto moving belts where final sorting takes place. Broken shell and the odd blue mussels are discarded, and the clean, fresh, live mussels are fed into either specially designed one tonne transporting sacks or 25kg wholesale sacks for the local market. The vessel's on-board crane stacks the full sacks along the deck as they are progressively filled.
These self-contained harvesting vessels employ a crew of between three and six depending on size.
The larger vessels can harvest over 100 tonnes of washed, separated, ready-for-processing mussels a day. They are self-propelled and can move quickly between farm sites to the nearest unloading point. These specialist vessels are all of shallow draught so that the state of the tide will not unnecessarily delay access to wharves or slow the delivery process.
The mussel industry is poised to become a major export earner and one of our largest coastal employers, which is a win for both the government's coffers and local communities.
In 1988 New Zealand exported 5800 tonnes of greenshell mussels valued at $24 million FOB. A decade later exports by weight peaked at 33,100 tonnes valued at $118 million, and in 2002 the country earned $185 million from 28,810 tonnes.
While the aquaculture reforms are proceeding through parliament, progress on aquaculture marine areas is becoming bogged down as local bodies and Maori start debating who should have control.
When I look around our coast I see two major future opportunities for our industry - mussels and logs.
The mussel industry has opened up a whole new opportunity for our boatbuilding and supporting marine industry, of which only a few companies have really made a mark. Besides the hull and deckhouse construction, these vessels are a hive of machinery and hydraulics driving harvesting gear and sea cranes. Some vessels provide live-aboard accommodation, while others are mainly set up as day boats. All this on-board equipment and marine farm materials has to come from somewhere. While many companies have secured a niche, the opportunities for other responsible manufacturing companies and suppliers to create market share is wide open.
Unlike the America's Cup, there will be no gravy train and fewer opportunities for the quick buck fly-by-nighters. But for those who do their homework and build relationships based on quality workmanship and service the future is bright, and like the mussels, 'Alive, alive 'o.'

We thank the Mussel Industry Council for their research material used in this article.

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