Paua Polyculture

September 2007
Four years ago Hongoeka Development and NIWA got together to talk possible uses for a strip of coastal land that their people own at Plimmerton - north of Wellington.

The project began with an investigation of a low cost, ecologically balanced acquaculture system what the scientists call a polyculture - which allows maximum use of space while reducing waste.

What theyve come up with is a system for producing paua.


A pilot project to develop economically sustainable aquaculture systems that make aquaculture accessible to Maori and small coastal communities in general.

Polyculture allows maximised use of space while reducing waste.

First time a polyculture system has been based around abalone.

Development of a low cost modular system for land-based aquaculture. Modularity allows extra species to be added.

Accessible Aquaculture

Maori participate in all aspects of the seafood industry but Maori involvement in the aquaculture industry is less than it should be. The barriers to greater involvement include high capital costs and long lag-times before profits are realised. This research programme uses polyculture technologies to develop economically sustainable systems that make aquaculture accessible to Maori.

The Hongoeka project

About four years ago the Hongoeka Development Ltd and NIWA got together

to find a way to establish an aquaculture project at a quarry site in Plimmerton. The quarry was closing and they were looking for a new development opportunity.

The idea of an aquaculture based venture was built around the concept of an abalone farm, where the waste was recycled to produce other high value foodstuffs. This concept had been applied to other systems worldwide, but had never been used where abalone were the main producer of waste within the system. The highly experimental nature of the project and its innovative nature are what attracted funding from the Foundation for Research, Science & Technology (FRST).

The project, within Hongoeka's overall plan, was one part a planned tourism, training and hatchery venture.

The polyculture system

Polyculture is a system of growing two or more species together in a single sustainable system. The aim is to achieve an ecologically balanced system that maximises growth of the main culture species while reducing waste and culturing additional species. This offers the potential to maximise economic value from limited aquaculture space while reducing impacts on the environment.

The initial species selection for the Hongoeka project was to be based around the concept of the waste produced by paua coupled to species that had relevance to Maori. NIWA offered suggestions and Hongoeka got to choose which ones they wanted.

The final selection was paua, karengo (removes dissolved ammonia), oysters remove suspended solids) and sea cucumbers (remove settled solids).


To produce paua plus one other commercial crop (seaweed) and include other species that are of benefit to water quality. Aim to produce 1 tonne of paua per year.

Reduce capital costs through low cost filtration systems to maintain water quality and low head loss to minimise pumping costs.

Map and manage changes in water quality through the system, including: suspended solids, nitrogen, pH.


A pilot polyculture system was developed and tested at NIWAs coldwater aquaculture research facility at Mahanga Bay, in Wellington Harbour.

Research progressed on two fronts simultaneously:

1. Designing a system that was low cost, low maintenance and robust.

2. Defining how well each species fitted within the system.

The system

The research succeeded in designing a robust, low maintenance system based on novel recirculation technology:

self-cleaning abalone tanks mean relatively constant input of suspended solids.

large suspended solids are removed using a simple settling basin (bioclarifier) which only requires cleaning every three weeks.

fine suspended solids are removed by foam fractionators.

The species

Paua: grew well in the pilot system at Mahanga Bay (2-3 mm per month was common). This is as good as any other farm in New Zealand and better than most. Growth rates in this recirculation system are better than in flow-through systems. However, more attention has to be paid to removing waste products and maintaining pH levels.

Oysters did not live in the system and were replaced by mussels.

Mussels: the filtering capacity of mussels is quite high and very few were needed to reduce the suspended solids load. Estimated capacity was just a few kg -certainly not enough to warrant any meaningful harvest from the system.

Sea cucumbers: research showed that this species, whilst efficient at eating settled solids and able to grow on waste from paua fed a natural algal diet, would not survive on the waste produced by paua when the paua were fed the artificial diets that are used in NZ. Some really useful data on sea cucumber energy budgets was derived, but sadly if they won't eat the solids in the system then they could not be included.

Seaweed: we have tested two species of red seaweed, Porphyra (karengo). Both can be cultured within the system and will remove some of the ammonia from the water. Were still investigating growth and ammonium uptake at various temperatures.

Current status of the system at Hongoeka

The system is based on paua and seaweed only. About 30,000 paua are now on site and seaweed will be introduced in the next week or two.

They have monitored several variables including : suspend solids, pH, ammonium, oxygen and temperature.

Facts and Figures

The full scale site is capable of holding 1 tonne of paua. It holds 23 cu/m of seawater, and there's 3 cu/m of new seawater entering the system each day.

Tipper buckets empty the water into multi lay trays. Each one holds about 40kg of paua. Water movement is crucial to the set up, keeping things clean.

The setup is modular so the system can easily be expanded.

Paua Industry.

NIWAs focus has shifted in the past five years from producing baby paua to the challenges of growing paua to marketable size. The main issues are slow growth rates, due to low temperatures in winter and poor water quality. The scientists believe these recirculation technologies are the solution to the problem.

In the past paua has been grown in flow through systems. These needed large volumes of seawater pumped directly from the sea. Its expensive additionally so to heat the water. Recirculation systems retain clean warm water, thereby saving power.

In 2002 a prototype was developed by NIWA in Wellington. They found paua grew 50% faster than those in traditional systems. They also think oxygen and pH have a big affect on paua growth rates.

In 2003 the first commercial scale paua recirculation system was contracted and another shortly after. The paua in both these farms are taking only 26 months to reach commercially marketable size of 75mm.

The technology is now attracting world wide interest

The Future

Once the system is fully functional Niwa and HD Ltd plan to continue their collaboration by running training courses at Plimmerton that combine the theory of paua farming and water quality management with practical experience. HD is also keen to turn the project into an ecotourism venture.