Huka Prawn Park

After years of perfecting farming techniques by trial and error, New Zealand’s only prawn farm has developed a winning business formula incorporating farming, tourism and hi-tech innovation.

The Huka Prawn Park near Taupo pioneered the use of wastewater streams and has become a famous aquaculture tourism venture.

Wairakei Geothermal Power Station is next to to the park, and the prawn farm has an arrangement to make use of discharge water from the station. Discharge from the plant sits between 96C and 98C with a flow rate of 450 metric tons per hour in winter, when night time ambient temperatures may fall to –2C. Wastewater from the plant provides sufficient low-cost and environmentally friendly heated water to the plant all year round.

The geothermal fluid is passed through a heat exchanger to heat water for grow-out ponds and tanks in the hatchery and nursery as part of the process of growing prawns for the onsite restaurant.

The park has 11 prawn production ponds and four dedicated prawn fishing ponds that remain between 27C and 31C. The design for the park was completed in-house, with engineers only required for the initial stages of building the system. A small staff maintains the system, which supplies a sustainable and eco-friendly 7.8 metric tons per year of prawns to the park’s restaurant from 4 hectares of ponds.

With resource consent to use discharge water from Contact Energy until 2026, the Huka Prawn Park looks set to continue to supply prawns to its busy restaurant for years to come, and low-temperature geothermal earth energy will prolong the attraction’s cost-effective energy supply.

Richard returned from time working overseas, looking to purchase a business that had both export and tourism opportunities. He identified the Huka Prawn Park (founded in 1987) as ideal with its strengths including being located in the tourist town of Taupo, the attractiveness of the site beside the Waikato River, and the opportunity to use heat from the adjacent geothermal plant to heat the farm’s water.

In 1991, he bought into the then non-existent tourism side of the business. That year a prawn restaurant was opened in an army tent on the side of the highway. The public loved it, providing the confidence to clear a site for building a restaurant on the riverbank.

The farming side of the business had some major problems, with breeding stock having run right down due to insufficient knowledge of farming techniques.

By 1995, Richard was a 50/50 shareholder in Huka Prawn Park with foundation shareholder, electrical engineer Terry Toomey. The farm was virtually shut down for a couple of years while they employed ‘Kiwi ingenuity’ to discover ways to re-build depleted breeding stock and increase production.

At the time, there wasn’t enough cashflow to employ specialist biologists, so the learning curve for the men was huge. The first challenge was to keep the Giant Malaysian Prawn breeding stock, which had been imported in 1988, alive.

Subsequent improvements included :

• increasing the sophistication of the heating plant
• trialing suitable foods for immature through to mature stock
• discovering the ideal water temperature, salinity and stocking levels for breeding (the biggest challenge) and growing prawns
• an innovative system of filtering the water that is recycled through the plant.

After massive experimentation, breeding problems were solved and cashflow improved enough to employ scientists to iron out the breeding and hatching systems for the farm and develop the technology to give the farm some security around the supply of prawns.

Richard says they are now at a point to start exporting their “know how” to other prawn farm operations in other parts of the world.

The Giant Malaysian Prawn species found at Huka Prawn Park was selected for its fast growth rates and resistance to disease.

Freshwater prawns have a hard outer shell that must be shed regularly for the creature to grow. Because of these periodic moults, growth occurs in increments, rather than continuously. This results in four distinct phases in the life cycle : egg, larvae, post larvae, and adult.

Breeding stock are kept in tanks indoors, dying at about two years of age. New breeding stock are brought in continuously, selected on size. A big female will produce 10,000-80,000 eggs versus 10,000-20,000 for a small female.

Females spawn up to five times a year and a 50 gram female can produce up to 50,000 eggs. Every three months or so, they snap out of their exoskeleton and become very soft and vulnerable to being eaten by others.

Each male has a ‘breeding flock’ of up to seven ‘ripe’ females. The males are jealous creatures, attacking other prawns which get too close and dragging into line any females that get too far away, with large pincers.

Within a few hours of mating, eggs are laid and transferred from the head to the underside of the tail.

When females are ready to spawn, which is indicated by their bright orange eggs turning brown, they are shifted out of fresh water tanks into a saltwater mix, essential for larvae survival and to replicate what happens in the wild when females migrate to an estuarine environment to spawn.

At the farm the females release their larvae and they are collected, and removed to a saltwater tank where they spend about a month.

Next, the post larval prawns are moved first to an indoor fresh water nursery, then to the ‘big wide world’ of the ponds to grow. Their diet is now a custom-made high protein shrimp and vegetable pellet.

The prawns are monitored regularly, netting a few and bringing them back to the laboratory to be weighed. They are ready to harvest from six to eight months of age, weighing around 30 grams on average.

The harvest takes place a couple of times a year, with the plug pulled on the pond in the evening and the harvesting crew picking up prawns the next day and grading them on size.

After harvest the ponds are left to dry and any waste material is removed.

Tourism has been the backbone of the business. Richard says the hatchery and farm, especially in the early days, were very expensive operations which sucked up money.

The restaurant has evolved into a tourist attraction for visitors to Taupo. In the beginning it was a tent and later a domed building with a roof kept up by air pumps. These days it’s a bigger, more solid and more profitable.

Some time ago Richard and Terry resolved to start developing tourism at the prawn park. These days there’s prawn fishing, which allows visitors to catch their own prawns and then get them cooked for free in the restaurant.