Huka Prawn Park; breeding, feeding and eating prawns

July 2006
This is New Zealands only prawn farm, producing up to 32 tonnes of prawns per year from 19 ponds, with around 99% consumed in the on-site restaurant.

Richard Klein, hands-on partner in the business, returned from time working as a mechanical engineer on oil rigs in the North Sea looking for a food 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 farms 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 became 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 wasnt enough cashflow to employ specialist biologists, so the learning curve for the men was huge. The first challenge was to keep the breeding stock Giant Malaysian Prawns 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

After massive experimentation, breeding problems were solved and cashflow improved enough to employ the two marine biologists (both ex oyster farmers) who work at Huka Prawn Park today.

Richard and Terrys engineering expertise meant they have been able to build and modify plant needed to achieve optimum conditions for farming.

In retrospect, Richard can see how valuable if desperate those years of experimentation were, giving him and Terry a good understanding of breeding and feeding productive prawns.

Huka Prawn Park uses waste hot water which would otherwise be released into the environment - from Contact Energys geothermal plant, via a pipeline. It is allowed to cool a little then goes through big heat exchanges (designed and built by Richard and Terry), which warm Waikato River water to 28 degrees celsius, ideal for prawn growth..

This helps the environment and helps us, with hot water a major cost in New Zealand.

New Zealand imports more than 2000 tonnes of frozen prawns per year, sold through restaurants and supermarkets. There is an opportunity to compete with fresh, chilled product.

Deloitte forecasts are that by 2020 50% of seafood will be grown by man.

Having consolidated by perfecting prawn growing technology as well as developing a successful restaurant/tourism business which generates 99% of cashflow, the company is now looking to expand both in New Zealand and overseas.

A couple of potential sites for a second North Island prawn farm are being considered, and opportunities for investment explored through Deloitte.

We are looking for a private investor, preferably with heat and land to offer.

It is likely a second farm could focus on local and/or export markets.

For six years, the company has been developing a pilot prawn farm in Iceland, in partnership with the Icelandic government. Geothermally heated wastewater is again used to heat the water. Small amounts of prawns have been sold through restaurants in Iceland and through UK supermarkets.

An investor (a prawn-fishing company) has now been found to finance the expansion of the Iceland operation to a commercial scale.

Niue is being considered as a possible location of another prawn farm, offering an ideal climate where water will not need to be heated.

Marine biologist, Andrew Harrison

The Giant Malaysian Prawn species found at Huka Prawn Park was selected for its fast growth rates and resistance to disease. If they escaped into the Waikato River they would not survive, because the water is so much colder than their ponds and they could not get to the sea to reproduce.

Freshwater prawns have a hard outer shell that must be shed regularly in order 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, postlarvae, 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 spawn 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. This is when mating takes place.

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 his 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 indicated by their bright orange eggs turning brown they are shifted out of fresh water tanks into a salt water mix, essential for larvae survival.

Larvae are skimmed out with a sieve, and removed to a salt water tank where they spend about a month being fed a diet of sieved mix of scrambled eggs and minced mussels. This process mimics nature, where females travel to river mouths to spawn, then return upriver.

Next, the post larval shrimps are moved to first an indoors fresh water nursery then to the big wide world of the ponds to grow. Their diet is now a custom-made high protein concentrate.

Andrew monitors the shrimps monthly, netting a few and bringing them back to the laboratory to be weighed. They are ready to harvest at about six to eight months of age, weighing around 30 grams on average (although there is a huge variation).

The harvest takes place most Wednesdays, with the plug pulled on the pond the previous evening and the harvesting crew picking up prawns the next day and grading them on size.

Algal blooms can be a problem for the farm, but these are overcome with the old farmers trick of placing a bale of barley straw in any pond affected.

There is next to no waste from the farm, due to sensible stocking. However, indoor tanks do need to be vacuumed occasionally (especially if a flood has filled them with silt) and ponds are cleaned out with a grader with the resulting muck taken home by staff for use in their gardens.

Adrienne Thompson

Huka Prawn Park is one of Taupos main tourist attractions drawing about 150,000 visitors a year. The main drawcard is the restaurant which seats 400, with diners consuming about 99% of the farms production.

There are four grades of prawns with the sweet-flavoured 30g the most popular. The significant number of Asian visitors especially enjoy the over 30 gram jumbos and smalls which they munch through unpeeled, head, tail and all. They often ask for females with eggs, regarded as especially delicious, but are out of luck here as eggs are water-blasted off to cater for majority taste.

Softs are peeled and minced for use in prawn burgers, chowder and pate.

Prawns are also supplied to two Taupo restaurants and 10-20kg/week is distributed through a Nelson fishing company.

In April, a 120 metre long bridge was built taking visitors from the hatchery to the fishing ponds. Here they can fish for prawns later cooked in the restaurant, ride prawn bikes and try teeing off across the ponds from a three metre golf platform.