Aquaculture

New Zealand’s aquaculture sector is a significant primary industry, estimated in 2015 to have revenue in excess of $500 million, of which about 75 per cent is exported to 79 countries. ¹⁶³⁸  Māori own an estimated 50 per cent of the aquaculture industry. 

The most commonly farmed species in New Zealand are the indigenous green lipped mussel, which is not farmed anywhere else in the world, the introduced Chinook salmon (also called King Salmon) and the Pacific oyster. Mussels are predominantly farmed in the Marlborough Sounds, as well as in Tasman and Golden Bay, the Coromandel Peninsula, Waiheke, Northland, Opotiki, Great Barrier Island, Canterbury and Stewart Island. King Salmon are farmed in the Marlborough Sounds, Canterbury and Stewart Island as well as South Island rivers. Pacific oysters are mainly farmed in the Far North, as well as at Coromandel, Auckland and Marlborough. New Zealand also has growing industries in pāua and seaweed. Other species, including kingfish, eels, geoduck clams and Hāpuku have been farmed or trialled as possible species of the future. ¹⁶³⁹  Land-based aquaculture is also a rising sector.

The high quality of New Zealand’s coastal waters, the abundance of plankton, and the prevalence of sheltered harbours and inlets means that the country has considerable aquaculture potential. ⁴⁵⁹⁵ The consumer demand for seafood (including shellfish) is rising internationally, at a time when global wild stocks are under pressure, creating growing markets for farmed seafood products. The relative sustainability of marine aquaculture compared with land based meat production ⁴⁵⁹⁶ and the human helath benefits of diets rich in fish ⁴⁵⁹⁷ are matters that are frequently referred to by those seeking to highlight aquaculture's potential. In 2006, members of the industry working with the former Ministry for Economic Development, released a strategy aimed at making aquaculture a billion dollar industry in New Zealand by 2025. ¹⁶⁴¹

The Government’s Aquaculture Strategy and Five-year Action Plan to Support Aquaculture, developed in 2012, sets out a “whole-of-government pathway” to support growth in the aquaculture industry. This includes developing new farming space, improving the use of existing space, and increasing the value gained from production. ¹⁶⁴²

Farming Mussels

The main harvestable mussel species is the native New Zealand green-lipped mussel (Perna canaliculus), the shell of which can be up to 260 mm long, 110 mm wide and 90 mm deep. ¹⁶⁴³  These mussels have been harvested for eating since humans first settled in the country. ¹⁶⁴⁴

A mussel farm consists of a series of rope ‘back-bones’ suspended in, or on top of, the water column by a series of buoys. A continuous rope (the ‘long-line’), on which the mussels are grown, is suspended from the back-bone line. ¹⁶⁴⁵  The backbone is anchored to the seafloor at either end. A three-hectare farm would typically have nine lines of 110 surface metres length each. Each line is supported by 50 to 70 large plastic floats. Each float may support one ton of mussels. One 110-metre line will generally support 3500 to 4000 metres of crop rope.

Many crop lines are seeded with mussel spat (juvenile mussels), with the majority sourced from Ninety Mile Beach in the Far North where, at irregular times throughout the year, large quantities of spat attached to seaweed are washed up on the beaches. This spat is collected and transported by air or truck to farmers in other parts of the country. The collection of this spat is managed under the Quota Management System (QMS) based on a management plan prepared in association with local iwi. A substantial amount of spat is caught on lines at locations in Golden Bay and Tasman Bay, particularly at Wainui Bay. A substantial amount of spat is caught on lines in Golden Bay and Tasman Bay, and particularly at Wainui Bay.  It is thought that spat travels from parent-beds on the West Coast of the South Island on currents which deaccelerate in the vicinity of Golden Bay.  At that point the spat are old enough to attach on to structures which they do in great quantities.  Local spat catching also occurs on a smaller scale at some other mussel farm sites in Jackson Bay and in some bays in the Marlborough Sounds. Substantial new areas for mussel farming and spat catching within aquaculture management areas in Golden Bay and Tasman Bay have recently been given approval through an aquaculture decision process assessing impact on other fisheries.

Traditionally, virtually all mussel stock farmed in New Zealand is collected as spat from the wild. However, in recent years there has been an increasing focus on the opportunities offered by the use of hatcheries, where mussels can be selectively bred for specific qualities such as higher meat yield and faster growth. Hatchery spat are grown from a “family” where the offspring are from two known parents. Each family may consist of several thousand siblings, grown together until they are large enough to transfer to the marine farm, with about 50 to 60 families per cohort needed to establish an effective breeding programme. ¹⁶⁴⁶

A team of scientists from SPATnz and the Cawthron Institute have been rearing 80 families as part of a Primary Growth Partnership programme between SPATnz, Sanford Limited and the Ministry for Primary Industries. ¹⁶⁴⁷  SPATnz’s grow-out trials commenced in April 2013 and the hatchery has now moved into commercial scale production. When fully developed, the SPATnz project anticipates being able to produce spat for around 30,000 tonnes a year of adult mussels. ⁴⁵⁹⁸

Once the spat are at the mussel farm, approximately 1000 to 5000 juveniles are wrapped onto each metre of rope, using biodegradable cotton stocking mesh. This mesh gradually disintegrates, by which time the spat have attached themselves to the rope. The mussels are left to grow for three to six months, and then these nursery lines are lifted and the young spat are stripped from the ropes, reseeded onto a final production rope at approximately 150 to 200 per metre, and then returned to the sea to grow. Mussels take between 12 and 18 months to grow to a harvestable shell size of 90 to 100mm. ¹⁶⁴⁹  The mussels are harvested by pulling the ropes up onto barges and removing the mussels. 

Offshore extensive farms hold some interest for the aquaculture industry. These can be several miles offshore (although still within the coastal marine area) and several thousand hectares in size. Due to the more exposed conditions offshore, the mussel lines must be spaced further apart to avoid entanglement. Such farms are still very much at the experimental stage, are untested commercially, and rely on substantial infrastructure investment before becoming viable.

In 2006, Eastern Sea Farms Limited, which is majority-owned by the Whakatōhea Māori Trust Board, was granted a license for a 3800-hectare marine farm to be established off the coast of Ōpōtiki. ¹⁶⁵⁰  The farm is sited three nautical miles offshore where the water depth and currents are suitable for mussel growing. The site has been chosen to minimise visual, navigational and environmental effects. It is away from sensitive habitats and important fishing areas. The planned marine farm will be the largest aquaculture venture in New Zealand, with the potential to produce approximately 20,000 tonnes of mussels per annum by the year 2025. ¹⁶⁵¹  There is also potential for further aquaculture development off the Ōpōtiki coastline.

Farming Oysters

Pacific oysters have been farmed in New Zealand since the 1960s. It is unclear as to when the Pacific oyster (Crassostrea giga) species arrived in New Zealand from Asia, but it is thought to have been in the late 1950s. ¹⁶⁵²  They soon started displacing the New Zealand native rock oyster and so farmers adopted the new arrival as their principal commercial species. 

Today Pacific oysters are the main farm-raised oyster in New Zealand. They are grown on wooden racks and baskets in sheltered and shallow intertidal bays around the northern North Island coast and in the Marlborough Sounds. The seed used to stock most farms is caught from the wild, predominantly from the Kaipara harbour. Oyster larvae drifting in the water settle on bundles of wooden sticks which are placed in the water column. The sticks are then transported to marine farms, where the larvae are transferred to racks for on-growing the baby oysters. Sometimes, the oysters are transferred to mesh bags, hanging baskets or wire racks for growing. Using baskets suspended on wires can be an effective method of farming, allowing oyster farms to be located in more exposed locations, because in rough weather the baskets swing and thereby resist the damage that would be caused to the traditional fixed racks. Pacific oysters grow to marketable size within 12 to 18 months. ¹⁶⁵³

A growing proportion of oyster spat is obtained from hatcheries where it has been selectively bred. Cawthron’s Pacific oyster breeding programme has seen growth rates more than 20 per cent higher than those normally achieved from a crop of wild spat. ¹⁶⁵⁴  Hatchery-bred oysters have become much more important to the industry, during the past couple of years, due to the devastating impact of the Ostreid herpesvirus (OsHV-1). Aquaculture New Zealand and the New Zealand Oyster Industry Association, through the Ministry for Primary Industries’ Sustainable Farming Fund, are undertaking a selective breeding programme which has been designed to assist the oyster industry overcome the virus. The programme is using selective breeding, and survival trials, to enable hatchery supply of reliably resistant juvenile oysters. ¹⁶⁵⁵  The oysters will be on-grown to bigger sizes, before they are transferred to locations where the water temperatures and environmental conditions create a risk of small oysters succumbing to the virus.

The endemic Flat oyster (Tiostrea chiensis) is referred to by a number of names, including Chilean oyster, dredge oyster and Bluff oyster. These oysters were found all over the coast, but particularly in extensive beds in the Foveaux Strait, Golden Bay and Tasman Bay, where they were dredged since the late 1800s. ¹⁶⁶⁶ Recently, the farming of flat oysters has been affected by the parasite Bonamia Ostreae.  It was first detected in the Marlborough Sounds and Nelson in 2015 and in May 2017 it was detected on two flat oyster farms on Stewart Island.

Farming King Salmon

New Zealand is responsible for approximately 70 per cent of the global King Salmon production. Sea pen farming of finfish has become widespread internationally, driven by a growing demand for fish and global pressure on wild stocks.  

New Zealand has no native salmonids, and only King Salmon (Oncorhynchus tshawytscha), which is native to the cool waters of the northern Pacific rim, have been successfully farmed here. Historically Sockeye has been farmed and Atlantic salmn have been trialled both unsuccessfully. After their introduction, King Salmon became established on the east coast of the South Island, and to a lesser extent also on the South Island’s west coast. Commercial farming of salmon started in the 1970s, both in inland ponds and in coastal waters. Today, most commercially sold salmon are grown in pens in the sea. ¹⁶⁵⁷

No imports of live salmon have been allowed into New Zealand for the last 100 years ─ instead eggs and milt are collected from captive broodstock. Fertilised eggs are incubated in a freshwater hatchery, where newly hatched fry are reared for another six to 12 months. The fish are then transferred to the sea pens, where they remain until they reach harvestable size, in about one and a half to three years. ¹⁶⁵⁸

Whereas shellfish feed on naturally occurring plankton, farmed fish such as salmon are top-end carnivores. They are fed an artificial diet of food pellets. Historically, much of the protein and oil in the feed was sourced from wild fisheries. However, in recent years, land-based proteins have increasingly been used to reduce the wild fish component. For example, Skretting Australia now produces fish pellets where only 28 per cent of the protein is from wild fisheries and 60 per cent is from land-animal proteins, with the balance derived from vegetables. Of the wild fishery component, just under half is sourced from fish processing wastage, with the rest consisting of wild-caught Peruvian anchovy. ¹⁶⁵⁹  Fish pellets are not currently manufactured in New Zealand because of the small size of the finfish aquaculture industry here.

Farming Indigenous finfish

The farming of indigenous finfish in New Zealand, such as Hāpuku (Polyprion oxygeneios) and Yellowtail kingfish (Seriola laland), has yet to occur on a commercial scale. Interest in the development of finfish aquaculture in the FirthofThamesandsouthern Hauraki Gulf led the government to legislate a zone of approximately 390 hectares for the culture of Yellowtail kingfish and Hāpuku in the Waikato regional coastal plan. ¹⁶⁶⁰  A resource consent is still required before such farming can proceed. Ngāi Tahu held a resource consent to farm a number of species including Hāpuku in Beatrix Bay, Marlborough Sounds.  That trial has ended, but resource consents are still in place. 

Currently there is limited information available about the specific finfish farming methods which might be adopted. However, assessments of the anticipated impacts of such farms have assumed that the two finfish species would be grown in floating sea-pens, with juvenile stock sourced from land-based seawater hatcheries. Plastic circular pens (typically 28 to 51 metres in diameter) are anticipated because the wave energy is expected to be too great for the square metal pens used at the South Island salmon farms. ¹⁶⁶¹

Hāpuku

Hāpuku is a member of the Polprionidae or wreckfish, which is comprised of nine species of largefish that live and feed on or near the bottom of the sea. Hāpuku is large and thick bodied, reaches 150 cm in length, and can vary in colour from silver and blue, to a pink, brown and silver combination. Most often found in deep waters over a depth range of 50 to 854 metres, this species is found throughout southern waters, and is common in the waters around New Zealand and Australia. Where stocks are still abundant (such as around the Chatham Islands) the species is known to frequent shallow waters. Unlike kingfish, hāpuku is a winter spawning species producing eggs in late July to early September. ¹⁶⁶²  NIWA and Plant and Food has been undertaking detailed research on growing hāpuku in controlled environments and these early trials indicate that the species could potentially be farmed in New Zealand.

Yellowtail kingfish

Yellowtail kingfish are widely distributed throughout the warm–temperate waters of the southern hemisphere. New Zealand kingfish, also known as kingi or yellowtail, are found from the Kermadec Islands to Banks Peninsula during the summer months. In the wild they can reach 1.7 metres in length and weigh 56 kilograms. Commercial catches of New Zealand kingfish are small, seasonal and unpredictable. Closely related species are commonly farmed overseas, in countries such as Japan and Australia.

Research undertaken by NIWA indicates that kingfish could be an attractive aquaculture species for a number of reasons including: ¹⁶⁶³

• It is highly valuable (earning up to $17 per kilogram on the European market)
• It has a rapid growth rate (reaching marketable size of three kilograms in 12–15 months)
• It is amenable to aquaculture conditions
• It has excellent flesh quality for a range of product options (such as whole fillets, sushi and the highly valued sashimi)
• It has significant domestic and international market opportunities

Around 500,000 kingfish fingerlings per year could be produced from NIWA’s facility in Northland, which would meet the needs of the early stages of an industry in New Zealand. Research is now focused on selective breeding, and the on-growing technology, including the setting up and running of sea pens to grow the hatchery-produced fingerlings to marketable size. ¹⁶⁶⁴

Eels

Freshwater eels are found in many river systems and lakes throughout New Zealand. Worldwide eel aquaculture is estimated to be worth over US$1 billion, accounting for 65 per cent of total eel production. Asia and Europe are the largest eel markets, but a decline in glass eel (returning juvenile stage) stocks in both regions has opened up opportunities for exploitation of species in other areas. ¹⁶⁶⁵

Eel farming involves catching juvenile eels, when they enter freshwater from offshore spawning areas, and on-growing them to a marketable size. Glass eels can be grown to maturity in two years in captivity. Eel aquaculture requires knowledge of upstream glass eel migration patterns, together with effective collection methods, and appropriate water quality and temperature conditions for culture. ¹⁶⁶⁶

As there is also a commercial and customary eel fishery in New Zealand, there is some opposition to the farming of eels if it is to be at the expense of the wild fishery, the management of which is currently being reviewed by the Ministry for Primary Industries. Primarily the limitation for further development is the need to close the breeding and early rearing phase so as to reduce/remove reliance on the wild elver returns. 

Last updated at 1:55PM on February 2, 2018